1: “I WISH TO WORK MIRACLES”

2: “GENIUS SO ELEVATED”

3: “PAINTER TO LUDOVICO”

4: A HORSE FOR FRANCESCO

5: THE DUKE'S FAVORITE

6: A LADY’S IRON WHIM

7: TO SERVE THE BORGIAS

8: NEW COURSE FOR THE ARNO

9: THE RIVALS

10: PAINTING SWANS - AND FLYING?

11: THE ARTIST AS TROPHY

12: CRADLED BY A KING

GALLERY

NEW WORD CITY

COPYRIGHT

Leonardo da Vinci personified the Renaissance, the extraordinary age in which he lived. Born a bastard in a hillside town in northern Italy, he became the protégé of princes, popes, and kings. Though many of his projects went unfinished, he set new benchmarks in painting and created stunning works of architecture, sculpture, and the written word. He mastered so many branches of science that scholars still debate whether he was more accomplished as an anatomist, botanist, cartographer, engineer, geographer, or naturalist.

By the time he died in 1519, Leonardo seemed to have accomplished his boyhood ambition: “I wish to work miracles.” Nevertheless, he died unhappy, believing he had failed to live up to his potential.

Leonardo’s genius set the standard that Western civilization still struggles to attain, and he serves as a reminder of the untold breadth and depth a single brilliant mind can span.

After the gloom and superstitions of the Middle Ages, the Renaissance that began in the early 1400s dispelled the immense cloud suspended over a Europe devastated by plague and war. A new spirit of intellectual rigor and scientific inquiry spread through universities and monasteries, where unconventional notions of liberty were born and depictions of nature appeared in a fresh guise. Artists and sculptors, confined for generations within the conventions of medieval art, embraced and explored naturalism and new forms of human expression. It appeared to many that a new world was emerging, one where people would be freed by reason and knowledge and all the secrets of the universe could be found and put to use.

At the center of this vortex was Florence, but as the new era expanded, it became evident that the Renaissance would transform all of European civilization and eventually the world.

The man who came to personify the era, Leonardo da Vinci was born on April 15, 1452. Widely admired in his own day, he left a posthumous treatise on the art of painting - 7,000 pages of manuscripts and 3,000 pages of notes filled with his writings and drawings. Yet at his core, he remains a puzzle. “Leonardo is the Hamlet of art history,” wrote scholar and art critic Kenneth Clark, “whom each of us must recreate for himself.”

What we know of him is pieced together from surviving church and town records, a few contemporary letters, and brief accounts of his life written in the century after his death. Scholars and historians have expanded that material into nuanced, insightful studies, but they remain partly speculations. “His mind and personality seem to us superhuman,” noted art historian Helen Gardner, “the man himself mysterious and remote.”

Leonardo sprang from the provincial village of Vinci, and lacking the pedigree to warrant a surname, he made do with da Vinci - “from Vinci.” The town was a long day’s ride - and an even longer cultural journey - from Florence twenty miles away. His family history gave no hint of greatness. Leonardo’s father, Piero, was a notary charged with handling the legal affairs of the town. The people of Vinci called him “Ser” or “Master” out of respect. Ser Piero da Vinci was a link between the slow, backward town - a cluster of stone buildings around a castle and a church - and the wealth and glamour of Florence, where he had many friends among the city’s artists, craftsmen, and merchants.

Leonardo was born from Piero’s liaison with a young woman named Caterina. She is usually described as a peasant, but the only early biographer who mentions her - Anonimo Gaddiano, who wrote about the lives of several Renaissance artists in 1540 - said she came “of good blood.” The baby was baptized the next day in the parish church in a rough stone font. Some eight months later, Piero married the bride his family had chosen: sixteen-year-old Albiera di Giovanni Amadori, daughter of another prosperous notary. After Albiera proved childless, young Leonardo, who had spent his first five years in his mother’s house, moved in with Piero and Albiera in their home just outside the castle walls. There he found ample affection from his stepmother and Piero’s younger brother, Francesco, who made time to play with Leonardo and take him for long walks in the Tuscan countryside.

Vinci sat high on the slopes of Mount Albano, between the olive trees and orchards of Lucca and the rugged mountain range with its rushing streams, twisting paths, and dramatic vistas, and uncle and nephew delighted in exploring the valley below Florence. These walks gave the boy a love of nature and its creatures. Giorgio Vasari, himself an accomplished painter, wrote of Leonardo in 1550: “He took an especial delight in animals of all sorts, which he treated with wonderful love and patience. For instance, when he was passing the places where they sold birds, he would often take them out of their cages with his hand, and having paid whatever price was asked by the vendor, he would let them fly away into the air, giving them back their lost liberty.”

Leonardo himself told only two stories of his childhood. The first, which he took as an omen, has usually been interpreted as a fantasy, but he wrote of it as a vivid vision of a hawk hovering over him: “. . . I was in my cradle . . . a kite came to me, and opened my mouth with its tail, and struck me several times with its tail inside my lips.” Leonardo was taking notes on the flight of birds when the memory struck him, and he preceded the story with this line: “Writing like this so particularly about the kite seems to be my destiny, since the first memory . . .”

The second story rings with both authenticity and hidden meanings. He wrote that while walking alone, “I came to the mouth of a huge cavern before which for a time I remained stupefied . . . my back bent to an arch, my left hand clutching my knee, while with the right I shaded my eyes; and I bent first one way and then another in order to see whether I could make out anything inside, though this was almost impossible because of the intense darkness within. And after remaining there for a time, suddenly there were awakened in me two emotions, fear and desire: fear of the dark, threatening cavern and desire to see whether there might be any marvelous thing in it.”

Leonardo seemed not much different from other boys, but the older he grew, the more he felt like a misfit in Vinci – not just because he was illegitimate and a stepchild, but because of his intense intelligence and curiosity.

Leonardo described himself as an “unlettered man,” because he had not been taught the formal language of Latin. His education was haphazard and informal, and he dropped a subject as soon as he learned what he wanted to know. “He would have been proficient at his early lessons if he had not been so volatile and unstable,” Vasari wrote. “He set himself to learn many things only to abandon them almost immediately. When he began to learn arithmetic, in a few months he made such progress that he bombarded the master who was teaching him with questions and problems and very often outwitted him.” Perhaps because he was left-handed, he took to his famous mirror-writing - from right to left on the page, with each letter formed in reverse. Viewed in a mirror, it looks like normal handwriting. The boy was fond of music, Vasari reported, and “he never left off drawing and sculpting, which suited his imagination better than anything.”

As he grew older, Leonardo regretted this magpie style of learning, but it’s doubtful he could have absorbed half as much had he been more methodical. In any case, he could not have progressed in a more formal education; because Piero never married Caterina and legitimized him, Leonardo could not have entered a university.

Leonardo had a talent for drawing. He kept a collection of snakeskins, bird eggs, small animal skulls, insects dried on pins, and odd-looking plants in his room and made repeated sketches of them. His father provided him with as much paper as he wanted, a precious resource in those days. Looking over the boy’s work one day, Piero made the obvious connection: His son could become an artist.

When Leonardo reached the age of fourteen or fifteen, Piero took a crucial step. On one of his frequent visits to Florence, he brought along a selection of the boy’s drawings and showed them to his friend, the painter and sculptor Andrea di Cione, known as Verrocchio.

Beginning as a goldsmith, Verrocchio had become one of Florence’s most illustrious painters and sculptors. After making his fortune working for Pope Sixtus IV in Rome, he had come home to Florence to establish a studio and a school. His apprentices and associates included such famed artists as Domenico Ghirlandaio, Pietro Perugino, Sandro Botticelli, and Lorenzo di Credi. Verrocchio immediately agreed with Piero that Leonardo was talented, and the boy moved to Florence to start his apprenticeship.

Florence in 1466 was home to 50,000 people, studded with 108 churches, twenty-three grand palazzi, and no fewer than fifty piazzas of varying sizes. It was a city of craftsmen, with 270 woolworkers’ shops and eighty-three silk makers; the eighty-four woodcarvers outnumbered the butchers. Little more than twenty years after Johannes Gutenberg built the first printing press, Florence was full of books – not only religious works, but volumes of maps, books on math and astronomy, and the writings of Aristotle, Plato, and other great philosophers. Leonardo devoured them and began collecting books of every description.

Florence was ruled by the greatest of all the dynasties in the Italian city-states. The Medicis were financiers, statesmen, warriors, popes, and patrons of the arts. Beginning as wool merchants in the 1300s and then as bankers, they became most likely the wealthiest family in Europe. Around 1400, Giovanni di Bicci de’ Medici opened the Medici Bank and quietly emerged as the most powerful man in the city. When he died in 1434, his son Cosimo assumed his mantle. Neither held formal office, but they ran Florence behind the scenes, rewarding their friends and bankrupting their enemies.

Cosimo controlled Florence for thirty years and expanded the city’s influence by taking over Arezzo, Livorno, and Pisa, successfully keeping a balance of power with the rival city-states of Milan and Venice. After his death, his weak and ailing son Piero ruled for only five years; then Piero’s son, just twenty years old, began the twenty-three-year reign that won him the name Lorenzo the Magnificent. Lorenzo was the patron of Leonardo’s teacher, Verrocchio, and may have helped Leonardo in his early career.

Apprentice artists in those days might begin work around the age of ten, setting out on a long path to learn their craft and become members of the artists’ guild. Leonardo lived in Verrocchio’s house; in return for food, lodging, and education, he did various chores around the workshop.

Verrocchio’s apprentices swept the floor and kept the studio tidy. Slowly they learned the secrets of master painters – for instance, how to prepare wooden panels for painting. Canvases weren’t yet used, and the seasoned wooden panels were first boiled to prevent them from splitting, then dried, coated with glue, and given another coat of gesso, a fine plaster used to provide a smooth surface for the paint. The paint used in those days was egg-based tempera, with colors ground by hand from minerals and chunks of raw pigment, another chore for the apprentices. Brushes were made from bundles of animal hairs stuck into wooden handles.

The apprentices also tried their hand at sculpture, working with chisels in both wood and stone. They drew with chalk or pencils, beginning with studies of folds of cloth and progressing to figures drawn from plaster casts or live models. They learned proportion and perspective and molded figures out of clay or wax. Leonardo was an eager student, quick to learn and always willing to attempt a new technique.

He showed both aptitude and originality. According to Vasari, a peasant in Vinci had made himself a round shield and asked Piero da Vinci to have it decorated. Piero took it to Florence to Leonardo, who painted the shield with an image of a monster spitting fire, a work so intimidating that Piero sold it to an art dealer in Florence for the considerable sum of 100 ducats. Piero then bought a shield decorated with a heart pierced by an arrow, which he handed off to the grateful peasant. Vasari doesn’t say whether Leonardo got any of the profit.

The work of famed masters surrounded Leonardo - Florentine sculptors Donatello and Lorenzo Ghiberti and painters Fra Filippo Lippi, Andrea del Castagno, and Domenico Veneziano, all nearing the end of their careers.

The painterly vocabulary was exploding. Painters began to replace the flat gold backgrounds of medieval paintings with landscapes, many of them modeled on the Tuscan hills and valleys. Piero della Francesca had made a detailed study of perspective and was the first painter to study the science of light. Dutch and Flemish painters introduced new themes and techniques that would revolutionize Italian painting. Filippo Brunelleschi had figured out how to use perspective and shading to make paintings appear three-dimensional. Botticelli used billowing draperies, blowing hair, and blurred lines to suggest movement in his paintings. The Sicilian Antonello da Messina, who worked only in oil paint, arrived in Venice, where the acknowledged master Giovanni Bellini saw his work and all but abandoned tempera in favor of oils. And in Verrocchio’s workshop, Leonardo was soon using oils to touch up and enhance details of the studio’s tempera paintings.

A popular artist, Verrocchio got many commissions. Most patrons wanted portraits of themselves and their relatives or religious paintings that focused on the lives of Christ and the saints. In religious scenes, patrons would sometimes appear kneeling reverently to one side. Still-life drawings and landscapes were used only incidentally, as background for the paintings, and apprentices and journeymen artists often got the job of painting backgrounds and details of costumes, curtains, and the like. Leonardo soon developed a masterly touch for crisp detail and specialized in curly hair, every strand distinct. The small white dog trotting along with Verrocchio’s “Tobias and the Angel” is unmistakably Leonardo’s work.

Since Verrocchio wasn’t just an artist but a skilled engineer, his apprentices also got a grounding in mathematics and structures and many elements of carpentry, metalworking, chemistry, metallurgy, leatherworking, and plaster casting. Leonardo soaked it all up and hungered for more. The studio could turn from casting a bronze bust to painting a portrait to building the framework that would combine three paintings into an altarpiece. Verrocchio was once hired to make a gilded copper ball to top the cupola of the Cathedral of Florence, Santa Maria del Fiore. That, too, was grist for the apprentices’ mill – as was the formidable chore of hoisting the two-ton ball to the top of the cathedral, securing it there, and placing a cross on top.

When his apprenticeship ended in 1472, Leonardo, at twenty, was admitted to Florence’s painters’ guild. As an acknowledged master, he could now accept commissions, employ craftsmen, and have his own apprentices. For several years, however, he chose to stay on as a paid journeyman for Verrocchio. He was trusted to take on more difficult parts of the paintings, including whole figures.

During this time, Leonardo collaborated with Verrocchio on a painting depicting the baptism of Jesus. Verrocchio painted the majority of the picture, but one of the two angels beside Christ is Leonardo’s. In the painting, Jesus is standing in a rocky stream while John the Baptist pours water over his head. Leonardo’s angel has an upturned face with a hint of a smile, and he looks kind and wise, so full of life that the rest of the painting seems stiff in comparison. The background, also painted in oil by Leonardo, is innovative for the time. Unlike most contemporary background landscapes with unnatural, sharply outlined trees, mountains, and other features, Leonardo’s background is fuzzy and unclear, with solid, three-dimensional features that appear blurred, as they would when seen far off by the naked eye. This gives the painting depth, with the figures in the foreground jumping out in relief.

As Vasari tells the story, when Verrocchio saw Leonardo’s finished work, he put away his brush and never painted again. That story may well be apocryphal, but it’s true that Leonardo took over more and more of the studio’s painting work, while Verrocchio concentrated on sculpture, which he seemed to prefer.

Leonardo’s next major work was “The Annunciation,” a larger painting that seems to be mostly his own. It shows the angel Gabriel appearing to the Virgin Mary, telling her she will give birth to the Son of God. Although it is not fully realized, “The Annunciation” shows Leonardo’s increasing mastery. Notably, his Virgin is neither submissive nor surprised by the angel’s news; she is serene and composed, with a finger marking her place in the scriptures she has been reading.

Still in his early twenties, Leonardo produced other notable works in Verrocchio’s studio: a second, smaller Annunciation for a cathedral altarpiece, and “The Virgin with the Flowers,” one of several small altarpieces of the Virgin and Child he painted. His final drawing for a tapestry of Adam and Eve in a flowery meadow was widely praised. He also completed his first known portrait, of a prominent young Florentine woman, Ginevra de’ Benci. Regarded by some as Leonardo’s first masterpiece, it’s a clear departure from the style of Verrocchio’s workshop. Ginevra – young, beautiful, and rich – was one of the city’s social celebrities born into the family of one of Lorenzo de’ Medici’s bankers. The portrait is an enchanted scene; the viewer has a sense of looking into it as if through a window as Ginevra sits uncannily still with heavy eyelids and glowing alabaster skin, gazing distractedly into the distance. The only hint of motion is the small cascade of ringlets surrounding her face, accenting the portrait’s stillness and mystery.

With his reputation on the rise, Leonardo left Verrocchio’s workshop and set up his own studio when he was twenty-five. He had spent ten years with Verrocchio, but now he was on his own in a hotly competitive market.

The art scene in Florence was a fraternity of sorts, and Leonardo associated with other prominent men – Sandro Botticelli, Filippino Lippi, Domenico Ghirlandaio, Pietro Perugino, Andrea della Robbia, and the Pollaiolo brothers, Antonio and Piero. He had patrons who gave him commissions and paved the way to commissions from others.

Leonardo’s first commission in his own studio, an altarpiece for the Chapel of San Bernardo in the Palazzo Vecchio, came in 1478. He received an advance on his fee, but the subject he chose is not known, and he never completed it. The job was given five years later to Ghirlandaio, who was displaced in 1485 for a new painting by Filippino Lippi.

Why did Leonardo forsake his first major commission? No one knows, but it was an omen: Leonardo was to abandon many projects, while much of his completed work deteriorated and crumbled because his quest for innovation kept him experimenting with new materials and techniques. However brilliant such work may have been, it couldn’t stand the test of time. In the end, Leonardo’s reputation rests on only fifteen paintings that scholars agree are his. His Florentine contemporary, the satirist Pietro Aretino, wrote, “I say to you that Leonardo was equal to the greatest. His limitation was that he had so elevated a genius that he was never satisfied with what was done.” In the case of the altarpiece, perhaps he was simply a perfectionist who couldn’t produce the vision he saw in his mind’s eye. Or perhaps, as with many later projects, he was sidetracked while studying his subject and jumped into a new one. His restless curiosity often stood in the way of earning a living.

The constant political turmoil in Florence was an endless distraction. Never a tranquil city, it was again being dragged into war. Throughout the early 1400s, the city had been sucked into clashes between the popes and the Holy Roman Emperors and also caught up in conflicts with the rival city-states of Italy. In 1440, Cosimo de’ Medici triumphed for Florence over the Viscontis of Milan in the Battle of Anghiari. The Medicis were also bankers for Pope Sixtus IV. But when Cosimo’s grandson Lorenzo broke with Sixtus, the pope turned over his finances to the Pazzis, a rival family of Florentine bankers.

In 1478, just as Leonardo was striking out on his own, the Medicis’ quarrel with the Pazzis erupted into a spectacular assassination in Florence’s cathedral. As Lorenzo de’ Medici and his brother Giuliano knelt in prayer, two men – Francesco de’ Pazzi, one of the heads of the family, and Bernardo di Bandino Baroncelli, a banker for the Pazzis – ran up with daggers drawn and stabbed Giuliano nineteen times. Two other assassins, dissident priests, attacked Lorenzo. Giuliano bled to death on the cathedral floor; the wounded Lorenzo was hurried to safety.

The attack was part of an attempt to overthrow the Medicis, but it failed. The conspirators were hunted down by infuriated mobs, and some twenty of them were killed. The Medicis hailed their triumph by commissioning Verrocchio to produce three life-size wax figures of Lorenzo with a scarf around his wounded neck, just as he appeared at a window of the Palazzo Medici; Botticelli was paid forty florins for a painting of the hanged assassins.

The Pazzi plot provided a telling sidelight on Leonardo’s relationship with Lorenzo de’ Medici. Assassin Bernardo Bandino hid in the bell tower of the cathedral and escaped the mobs, but a year later was tracked down in Constantinople, bought back to Florence in chains, and hanged from a window of the Bargello. Leonardo sketched his dangling body, with notes on the colors and style of his garments, indicating that he meant to do a full painting. But if he hoped for a reward like the ones Verrocchio and Botticelli had won for providing Medici propaganda a year earlier, he was disappointed.

In the following years, the Medicis’ feud with the pope escalated into a war that divided most of Italy. Inevitably, Leonardo was drawn to the conflict. While he had no experience in warfare, Verrocchio had taught him that an artist could design anything. Later, he would call war “beastly madness,” but at the time, he draw war machines, including armored cars, a machine gun, and even a submarine, complete with a conning tower and screw propeller.

Some were practical; others were not, because they relied on faulty theories or because they couldn’t have been built by fifteenth-century artisans. But all were ingenious.

The war raged for two years until Lorenzo de’ Medici brought it to a close by a daring stroke of diplomacy: With only a small retinue, he traveled to the enemy city of Naples, whose king, Ferrante, had sent his armies to reinforce the pope. The king might well have captured or killed Lorenzo, but the Magnificent used his charm to persuade Ferrante to desert the pope’s cause and back Florence instead. Without Naples, the papal assault collapsed. Lorenzo made a truce with Pope Alexander VI and with the pope’s former allies, the Sforza of Milan. With the return of an uneasy peace, Florentines again focused on the arts.

Leonardo was still trying to establish his studio. He won some minor commissions for small religious works and portraits, but lacked major projects.

One of his interests in the late 1470s and early 1480s was poetry. While Leonardo himself produced little verse, his Florentine circle included a group of burchiellesco poets – wry, slangy, rough-edged, and often bawdy writers. He was especially friendly with Antonio Camelli, known as “Il Pistoia,” a satirist whose style was summed up by a contemporary as “jokes, salt, and honey.” Leonardo’s notes and papers during those years also contain frequent references to prominent scholars, physicians, scientists, and mathematicians; he knew Leon Batista Alberti, sometimes called the “first Renaissance man,” and he had contacts within the intellectual circle of philosopher Marsilio Ficino.

Leonardo was also nurturing his lifelong passion for technology, further developing the hoists and cranes originally designed by Brunelleschi that lifted the great ball atop Florence’s cathedral when Leonardo was Verrocchio’s apprentice. According to Vasari, Leonardo offered the Signoria a plan to raise the entire Baptistery several feet and place a set of steps beneath it. “His arguments were so powerful that many people were persuaded it could be done,” Vasari wrote, “until they left his company and thought it over and realized it was impossible.” Leonardo’s drawings included a device for ripping the bars from a prison window, machines for pumping water to elevated tanks, and water-powered machines.

His studio included at least one apprentice, Tommaso Massini. Massini - who was to become a longtime friend, assistant, and general factotum for Leonardo over the next twenty-five years – was a flamboyant, talented, and likable man who was given a series of nicknames but was buried under a tombstone inscribed with the best-known one: Zoroastro.

The son of a gardener in a village near Florence, Zoroastro claimed to be the illegitimate son of Bernardo Rucellai, brother-in-law of Lorenzo the Magnificent. Rucellai, also a patron of Leonardo, took an interest in Zoroastro and may have helped place him in the studio. Zoroastro became a metalworker and a magician, an expert in casting bronze, and something of a court jester, but was also trusted with the household money and purchases. A vegetarian like Leonardo, he “would not kill a flea for any reason,” wrote one biographer, and “preferred to dress in linen so as not to wear something dead.” Later in life, Zoroastro took up alchemy. He seems to have been universally liked and respected – in the words of his epitaph, “a man outstanding for his probity, his innocence, and his liberality.”

During this period, Leonardo produced three notable works. The first, the “Benois Madonna,” is a small gem: Flawed in detail, seemingly unfinished, and showing signs of later repainting, it is nonetheless an unforgettable depiction of Mary as an unsophisticated young mother, delighting in the baby on her lap as he takes in the beauty of a small flower. It is the essence of the Renaissance painters’ newfound ability to show spontaneous, informal human moments. As he would do in later paintings, most notably the “Madonna of the Yarnwinder,” Leonardo introduced a note of foreboding: The flower that fascinates the child is the bitter cress, a four-petaled member of the Crucifera family and a portent of his death.

The second, more powerful, striking work of Leonardo’s first Florentine period is “St. Jerome in the Wilderness.” Produced for an unknown patron and never finished, it shows the saint as a hermit in the Syrian Desert, anguished and emaciated, striking himself with a stone as he gazes at a crucifix. In the foreground is a huge lion, the saint’s symbol, posed in a sweeping curve with its tail in a counter-curve. The lion is lightly and powerfully sketched, but every muscle and tendon in the saint’s arm and neck stands out as if in an anatomical drawing.

In 1481, Leonardo received his first important postwar commission, an altarpiece for the monks of the monastery of San Donato a Scopeto, just outside Florence. Leonardo’s father had been handling the monastery’s business affairs and may have had a hand in obtaining the commission, but since the monks knew about the unfinished altarpiece in the Chapel of San Bernardo, the contract required Leonardo to finish the job in two and a half years at most.

Leonardo was paying a heavy price for his independence and lack of dependability. The monks gave him no cash in advance, and his payment was to be only about 150 florins in the form of a property in the Val d’Elsa, south of Florence. In debt to the monastery for sums advanced to buy pigments for the painting, he was buying food and wine on credit and decorating the monastery clock in return for firewood.

Leonardo chose the Adoration of the Magi as his subject, and he planned an ambitious tableau of the Nativity. In a series of detailed drawings, he worked out the painting’s perspective, changing it repeatedly and switching the sixty-seven figures around in intricately composed groups. Yet once again, after working on it for seven months, he gave up on his painting.

Leaving his altarpiece unfinished, he closed his studio and packed his goods and went to Milan. Along with hundreds of drawings and many notebooks, he made an inventory of his recent work, including: “. . . certain figures of St. Jerome . . . drawings of knots . . . some machines for ships [and] for water . . . many heads of old men . . . a Madonna, finished . . . another almost, which is in profile.” Zoroastro went with him, and so did Atalante Migliorotti, a model who would become a singer and maker of musical instruments. Leonardo also took a letter of introduction to Ludovico Sforza, his prospective new patron, describing the marvels of engineering that he could perform – and mentioning almost in passing that he could paint, too.

It was a major gamble. Leonardo wasn’t a boy with the world before him; he was a man of thirty, competing on unfamiliar turf with new and talented rivals for the favor of a patron he had never met. He knew how capricious any patron’s favor could be and how even a major talent could be spurned or ignored. But he had the certainty of a genius: He would prevail.

Ludovico wasn’t yet the actual Duke of Milan; he was acting as regent for his ten-year-old nephew, who was too young to take over when his father, Ludovico’s brother, was assassinated in 1476. But Ludovico kept the heir isolated and powerless. Burly, ruthless, and unscrupulous, he was called “Il Moro,” the Moor, because of his dark complexion and as a pun on one of his names, Mauro. (Quattrocento Italians were obsessed by puns, and Leonardo was no exception; several times he paired his name with leone, lion.) Ludovico liked his nickname and used a moor’s head as part of his coat of arms.

Ludovico wanted to reinforce the fortress of Casalmaggiore on the Po River, and Leonardo’s offer of military expertise probably caught his attention. Leonardo’s drawings in Milan include both an armored car and a portable cannon that “fires out small stones, almost as if it were a hailstorm” – an early version of the grapeshot widely used in naval and land battles of the eighteenth century.

Because he was a Florentine, Leonardo had a certain edge in Milan. The two cities had a relationship rather like New York and Chicago or London and Paris; Milan both recognized and resented the cultural superiority of Florence. There was a prominent Florentine faction at the court of Ludovico, including the Medici banker Benedetto Portinari, the diplomat Benedetto Dei, and the Hellenist scholar Bartolomeo Calco, Ludovico’s secretary, who had been hired to help “purify the coarse speech of the Milanese.” All were in the inner circle and could be of help to Leonardo.

The painter and architect Donato Bramante, regarded as the foremost artist in Milan at the time, soon became a good friend. But it was Leonardo’s friendship with two local painters - Ambrogio and Evangelista de Predis - that resulted in his first Milanese commission. The three were hired by a religious group, the Confraternity of the Immaculate Conception, to paint an altarpiece that became the dark, elusive, haunting “Virgin of the Rocks.” It was to hang in the Confraternity’s chapel in the church of San Francesco Grande, then the biggest church in Milan except for the Duomo.

Ambrogio de Predis was already established as a “painter to Ludovico,” but Leonardo’s reputation preceded him: The contract called Leonardo magister and assigned him to paint the central panel of the altarpiece, with Ambrogio de Predis responsible for the two smaller side panels and his brother Evangelista to decorate the frame. They were promised 800 florins and given a deadline of eight months. The content of the painting was stipulated in almost comic detail: The Madonna and Child would be grouped with a band of angels and two prophets, and each side panel would feature four angels singing or playing instruments. Perhaps needless to say, hardly any of this materialized.

The painting shows the meeting of the infant Christ with the infant John the Baptist during the Holy Family’s flight from Egypt. They are in a grotto in the wilderness. With Mary’s hand on his shoulder, John is worshiping the Christ child, who blesses the Baptist in return, while an angel, seated beside Jesus, points to John. The Virgin’s left hand hovers over her son with its own sign of blessing.

There are two versions of the “Virgin of the Rocks” - one at the Louvre in Paris and the other in London’s National Gallery. The painting in the Louvre is thought to be the original and entirely the work of Leonardo; the London painting was probably painted later and by both Leonardo and Ambrogio de Predis. The Louvre version better reflects Leonardo’s early Florentine style, with the Virgin’s lovely face, graceful pose, and long ringlets. The London version is darker and more austere, and the figures are equipped with haloes, which Leonardo usually shunned.

One theory that explains the two paintings holds that after the artists finished the first version, Ludovico himself bought it and sent it to Holy Roman Emperor Maximilian in 1493 when Maximilian married Ludovico’s niece. Antonio Billi, a sixteenth-century merchant who wrote extensively about Quattrocento artists, has a note supporting this account, and it is a matter of record that Ambrogio de Predis was at the imperial court in Innsbruck for the wedding. If it happened this way, the Confraternity could have used part of the payment from Ludovico to hire Leonardo and Ambrogio to paint the second version for their altarpiece.

The painters delivered an altarpiece in 1485, but a legal dispute over the payment followed. In 1492, still squabbling, Leonardo and the brothers asked the court again for a fair payment or for permission to take back the painting, saying they had another offer. Litigation with the Confraternity erupted again in 1503 and lasted for five years, again over payment for “Virgin of the Rocks.” It seems likely that this dispute involved the second painting.

Leonardo’s obsession with flying machines - a dream that would stay with him all his life – showed up again in Milan. He had drawn his first such machine in Florence in a doodle probably done between 1478 and 1480; it showed a bat-like wing over a pod for the pilot, with a control mechanism that allowed only limited movement of the wings, suggesting a glider rather than a machine designed for self-propelled flight. In his early Milan notes, he conveys the idea of air having substance: “See how the beating of its wings supports a heavy eagle in the highly rarefied air . . . Observe also how the air in motion over the sea fills the swelling sails and drives heavily laden ships . . . So a man with wings large enough, and duly attached, might learn to overcome the resistance of the air, and conquer and subjugate it, and raise himself upon it.” He even envisioned a helicopter, with a giant linen screw for a propeller, noting that if it were turned rapidly, “the screw will find its female in the air and will climb upward.”

It took Leonardo several more years to design the more complex ornithopter, a flying machine with wings that mimicked an eagle’s. Ever the pragmatist, he was already imagining what could go wrong in the air and what to do about it, and around 1485, he sketched a working parachute. In the shape of a pyramid, twenty-four feet square with pine poles bracing the open bottom, the design was eminently practical – as proved in the year 2000 when an English sky-diver built one and jumped from a hot-air balloon 10,000 feet above the Kruger National Park in South Africa. He floated down gently, taking five minutes to descend 7,000 feet. Then, because Leonardo’s parachute weighed nearly 200 pounds and might crush him on landing, the skydiver cut himself loose and made the final drop with a modern parachute. He reported “a feeling of gentle elation and celebration,” adding: “It took one of the greatest minds who ever lived to design it, but it took 500 years to find a man with a brain small enough to actually go and fly it.”

Leonardo’s notes show his mind ranging incessantly, with allegorical drawings of pain entwined with pleasure and virtue with envy. Perhaps because Milan was enduring a three-year bout of the bubonic plague, he was also musing about designs for the “ideal city.” Leonardo’s city would be built on two levels. The upper one was designed for pedestrian traffic, with shops, public buildings, palazzos, piazzas, gardens, sculpture, and loggias. The lower level, with tunnels and canals as well as streets, would be for warehouses, animals, carts transporting goods, and the dwellings of “ordinary” people. Leonardo recommended spiral staircases between the levels, noting that people tended to urinate in the dark corners of square staircases.

To this point, Leonardo’s notes were a jumble of loose sheets, which he would rearrange from time to time; over the centuries, they floated from hand to hand and can be roughly dated only by changes in his mirror-script handwriting and drawing style. But in the mid-1480s, he began keeping proper notebooks. The earliest of these, which scholars now call Paris MS B, is in the Institut de France in Paris; besides the ideal city and the ornithopter, it contains designs that include churches, submarines, a steam-powered cannon, and a helicopter.

Another early notebook, now in London’s Victoria & Albert Museum, features a series of drawings of Archimedean screws for lifting water, with a long spiral turning inside a snugly fitted tube to force the water upward. There are also notes on grammar and vocabulary, lists of books he owns, drafts of letters, abstruse riddles, architectural notes and drawings, satiric stories written to entertain his friends, and jokes. The jokes were dense with puns, which was sometimes their only point – for example, his tongue-in-cheek substitution of lauro, the bay-tree, for Laura, to whom the poet Petrarch addressed his love poems: “If Petrarch was so madly in love with bay-leaves, it’s because they taste so good with sausage and thrush.”

But the early success in Milan seemed hollow. After five years as one of Ludovico’s courtiers, Leonardo had little to show for it. There’s no record of any ducal commissions, stipends, or even handouts. One of Leonardo’s drawings involves remodeling a pavilion in the Sforza castle garden, but it’s unknown if the plan was carried out or whether Leonardo was paid for it. But then, in 1489 or 1490, Leonardo was chosen to paint Ludovico’s young mistress, Cecilia Gallerani.

Cecilia was in her mid-teens, the daughter of a good but not wealthy Milanese family, and her affair with Ludovico has been underway for some two years. By all accounts, he was so besotted with Cecilia that he was delaying his arranged marriage to Beatrice d’Este, daughter of the Duke of Ferrara.

The wedding did occur, in January 1491, if only because it was part of a triple alliance that would cement a new political order in northern Italy. As Ludovico married Beatrice, her sister Isabella married Francesco Gonzaga II, Marquis of Mantua, and her brother Alfonso d’Este, who would become the Duke of Ferrara, was being wed to Ludovico’s niece, Anna Sforza. The Gonzaga had feuded with the Visconti while they ran Milan, but the three marriages linked to the d’Este clan, one of the oldest in Italy, now gave Mantua Milan as an ally. And the parvenu Sforza now had both Ferrara and Mantua on his side.

Even after Ludovico’s wedding, however, the Ferraran ambassador to Milan reported that the duke had confided to him that he wanted to be with Cecilia and that Beatrice was refusing to consummate the marriage until he gave up his mistress. Soon, nature took a hand: Cecilia was heavily pregnant and was sent from Ludovico’s private rooms to an apartment in the city. Her son was born in May.

It was probably early in the pregnancy when Leonardo painted Cecilia’s portrait, “Lady with an Ermine.” Slim and graceful, fashionably but not richly coiffed and dressed, she is cradling an ermine – a kind of weasel whose coat turns white in winter. (In the portrait, the ermine’s pelt has been yellowed by layers of varnish.) Since the animal’s name in Greek is galè, it is a visual pun on her name, Gallerani. Perhaps more significant, Ludovico himself had recently been invested in the Order of the Ermine by the King of Naples and was using the title, L’Erminello. In Leonardo’s painting, the ermine is vigilant and muscular, with its claws clutching Cecilia’s sleeve, an obvious invocation of the duke guarding his treasure.

Like many of Leonardo’s works, the portrait has a twisting, pyramidal composition. Cecilia sits facing diagonally to her right, but her head turns back to her left; her expression is expectant, and her eyes focus on something or someone outside the frame, where the ermine seems to look as well. Cecilia’s skin is luminous, almost translucent, and her hand caressing the animal is so finely modeled that a close viewer can see each wrinkle around the knuckles and the flexing of the tendon in her bent forefinger.

The painting was an immediate success. Ludovico’s court poet, Bernardo Bellincioni, wrote in a sonnet: “O Nature how envious you are / of Vinci who has painted one of your stars, / The beautiful Cecilia, whose lovely eyes / Make the sunlight seem dark shadow.” Cecilia kept the portrait after her liaison with Ludovico ended.

The modeling of Cecilia Gallerani’s hand was no accident. By the late 1480s, Leonardo had begun the systematic anatomical studies that he would pursue for the rest of his life, underpinning his painting with scientific knowledge that gave his works lifelike energy and realism. He had studied anatomy under Verrocchio, which was reflected in the arm and neck of “St. Jerome.”

But Leonardo’s intellectual interest in anatomy led him far deeper into the subject than other painters considered necessary. Some of his contemporaries and early biographers deplored his scientific work as a waste of time. In the course of his life, Leonardo would dissect some thirty human cadavers, working without the benefit of refrigeration and in spite of the taboos and doctrinal bans of church and state alike. From the beginning, he probed well beyond the joints, tendons, and muscles visible in a painting; in 1489, he drew eight studies of a human skull in finely shaded detail from multiple angles, showing hidden features that no painting could ever reflect.

Leonardo’s interest was partly metaphysical: His notes show him searching for the “confluence of the senses,” a physical spot where common sense and the “vital spirits” postulated by medieval medical theorists might be found. In later life, his language would be simpler and more bluntly descriptive, but he would never give up his formidable task of learning how human bodies work. Among the endless topics he posed for himself: “Which tendon causes the motion of the eye, so that the motion of one eye moves the other”; “What sneezing is”; “shivering with cold”; “Describe the beginning of man, and what causes it within the womb, and why a child of eight months cannot survive.”

More pertinent to a painter – and more useful in teaching apprentices – were Leonardo’s studies of the proportions of the human body and the mathematical ratios of one part to another. His study of Vitruvius, the Roman engineer and architect, led to Leonardo’s most famous anatomical drawing, the “Vitruvian Man.”

The drawing shows a man, in two simultaneous poses, standing inside a circle and a superimposed square. The mirror-written text above the drawing quotes Vitruvius: “The measurements of man are distributed as follows: that four fingers make one palm, and four palms make one foot; six palms make a cubit [forearm];” and so on, down to the distance from the hairline to the eyebrows being identical to the distance from the tip of the chin to the mouth.

In the drawing, the man - with his feet together and his arms outstretched horizontally - stands within the square, illustrating that his reach is equal to his height. The second figure, with legs akimbo and arms raised higher inside the circle, makes a different point: “If you open your legs so much as to decrease your height by 1/14th, and raise your outspread arms until the tips of your middle fingers are level with the top of your head, you will find that the center of your outspread limbs will be the navel, and the space between the legs will be an equilateral triangle.”

By the late 1480s, Leonardo had set up his own studio in Milan, where he was an instant hit for his talent, among others, for playing a lyre of his own creation, described as a kind of violin – in the shape of a horse’s skull – with a silver soundbox. A talented musician, Leonardo “gave some time to the study of music and learnt to play on the lute, improvising songs most divinely,” according to Vasari.

The location of his Milan studio is unknown, but evidence indicates it included at least eight artists and apprentices, including the two De Predis brothers and the faithful Zoroastro. Two wealthy amateurs, Giovanni Antonio Boltraffio and Marco d’Oggiono, joined the studio not as apprentices but as associate painters, and under Leonardo’s eye both of them became notable artists. An early apprentice was Francesco Galli or Napoletano, who went on to his own degree of fame; his “Madonna and Child with St. John the Baptist and St. Sebastian” can be seen in the Zurich Kunsthaus. Another was a German called Giulio, like Zoroastro a metalworker rather than a painter.

Other newcomers to the studio would come and go, but one became part of Leonardo’s life for the next twenty-eight years. In one of his notes, he records, “Giacomo came to live with me on St. Mary Magdalen’s day [July 22] 1490.” Ten-year-old Giacomo’s father, an obscure villager named Pietro Caprotti, was willing to pay for his upkeep while the boy served as Leonardo’s servant, errand-boy, and studio model - and eventually one of his apprentices.

How soon Giacomo slept with Leonardo is a matter of conjecture, but there’s not much room for doubt that he did. As Vasari describes him, he “was extraordinarily graceful and attractive. He had beautiful hair, curled and ringletted, in which Leonardo delighted.” Another of Leonardo’s commentators, the artist Giovanni Paolo Lomazzo, was the first to assert Leonardo’s homosexuality, if only indirectly. In an imagined exchange between Leonardo and the long-dead Greek sculptor Phidias, Lomazzo has Phidias refer to Giacomo as one of Leonardo’s favorite pupils, to which Leonardo says, “. . . he was a very fair young man, especially around the age of fifteen.”

Giacomo was a special case – an unruly, mischievous, unmannered scamp who soon earned the lifelong nickname of “Salai,” an Arabic-rooted word meaning “little devil.” The list of Salai’s misdemeanors in his first year of service is impressive, as recorded by Leonardo, in what was presumably a draft of a letter to the boy’s father:

“On the second day [July 23] I had two shirts cut for him, a pair of stockings and a jerkin, and when I put aside the money to pay for these things he stole the money out of my purse, and I could never make him confess, though I was quite certain of it.

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“The day after this I went to supper with Giacomo Andrea, and the aforesaid Giacomo ate for two, and did mischief for four, insofar as he broke three table-flasks, and knocked over the wine . . .

“Item. On 7 September he stole a pen worth twenty-two soldi from Marco [d’Oggiono] who was living with me. It was a silverpoint pen, and he took it from his studio, and after Marco had searched all over for it, he found it hidden in the said Giacomo’s chest.

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Leonardo’s accounting to Salai’s father ends with a list of the boy’s clothing costs, and in the margin are four words: thief, liar, obstinate, greedy. But there is an unmistakable tone of rueful amusement in this indictment, and no hint at all that Leonardo wants to be rid of his imp.

Indeed, Salai stayed on - as model, servant, companion, and, in time, apprentice. But the relationship between the head of the studio and his student was never entirely smooth. On one sheet of notes are the words, “Salai, I want to rest, so no wars, no more war, because I surrender.” This was written in someone else’s handwriting almost as part of a shopping list, as if overheard. Whoever wrote it, Leonardo let it remain in his official notes.

Over the years, Leonardo spent heavily on luxuries for Salai, along with loans for expenses such as a dowry for Salai’s sister. Eventually, Salai took possession a house outside Milan that Ludovico had given Leonardo, renting it out and keeping the proceeds. And for the “good and kind services” Salai had provided, Leonardo left him the house in his will.

In the summer of 1493, a woman he referred to only as Caterina also joined Leonardo’s household. She could have been a servant, but is more likely to have been Leonardo’s mother. She would have been in her mid-sixties then, and her husband had died three years earlier. He made no further note of her until about two years later, when he listed the costs of her modest funeral.

Like the studios of other Quattrocento artists, Leonardo’s bottega turned out several kinds of works. Some were almost entirely his own doing, as in the portrait of Cecilia Gallerani. Paintings by his associates Boltraffio and d’Oggiono would benefit from his tutelage, criticism, suggestions, and perhaps even a touch of paint here and there. Such works wouldn’t command Leonardo’s price, but would be seen as from his studio. His apprentices might contribute varying amounts of work on drapery, backgrounds, or even a figure in a large scene, which would be priced accordingly.

In 1489, about the same time Ludovico hired Leonardo to paint his mistress, the duke gave him a far more important commission: to create a giant statue of Francesco Sforza, the duke’s father, in full armor, mounted on a horse. At the time, there were four notable equestrian statues in Italy, two of them dating from classical times, and Ludovico wanted his father’s monument to be bigger and grander than any of them.

Leonardo had been angling for this job since his first letter to Ludovico, in which he offered “to begin work on the bronze horse which will be to the immortal glory and eternal honor of the Prince your father’s happy memory and of the famous house of Sforza.” But even after giving him the commission, Ludovico seems to have had doubts that Leonardo could fulfill his vision; he had the Florentine ambassador to Milan write to Lorenzo the Magnificent asking if he could engage experts in bronze casting to assist with the job.

The duke’s misgivings were understandable. Casting bronze on such a scale would be a formidable task for anyone, and while Leonardo had probably helped Verrocchio with the planning of the great equestrian statue of Bartolomeo Colleoni in Venice, he had left the studio before Verrocchio did the actual casting. To make the job even more complex, Leonardo had conceived of something never before tried. The other four horses were sculpted in a trotting pose, with three feet on solid ground. Leonardo’s first sketches for the Sforza horse show it rearing on its hind legs – a dramatic but precariously unstable pose.

The horse was clearly the most formidable part of the commission, and Leonardo began with it, leaving the design of the armored rider aside for the moment. He explored at least two possible solutions to the technical problem of a rearing horse. In one, a fallen soldier connects one of the horse’s front feet to the ground; in another, the soldier has been replaced with a tree stump. But when Leonardo traveled to Pavia, some twenty miles south of Milan, to see the classical equestrian statue in the trotting pose known as Il Regisole, he was stunned by the realism of its arrested movement. It was probably there that he gave up the idea of a rearing horse. His field notes contain the line, “It is more praiseworthy to imitate antiquities than modern things”; all his subsequent studies of horses show variations of the trot.

Leonardo needed a huge studio to build the clay model around which the bronze would ultimately be cast, and Ludovico furnished one. Leonardo was installed in the Corte Vecchia, the dilapidated castle that had been the seat of the Visconti family until Francesco Sforza took over and began building his own Castello Sforzesca. Leonardo’s workshop was the former grand ballroom. Adjacent rooms served as his study, laboratory, and living quarters for the maestro and his helpers.

The model for the great horse was colossal: tons of clay packed around a supporting metal armature. It stood some twenty-four feet high. It was exhibited in November 1493 at the proxy marriage of Ludovico’s niece Bianca to Emperor Maximilian, and viewers were awed not just by its size but with its fine detail and spirited pose. “See how beautiful this horse is: Leonardo da Vinci alone has created it,” wrote the poet Baldassare Taccone, and Vasari noted, “Those who saw the great clay model that Leonardo made considered that they had never seen a finer or more magnificent piece of work.”

Ludovico had set aside approximately seventy-five tons of bronze for the casting, and as soon as the model was finished, Leonardo began planning the details of the casting process. He intended to cast the horse in a single piece, a challenge that some considered impossible. It involved making an outer mold of kiln-baked material, preserving every detail of the surface of the clay model, and supporting it with an armature of iron. The mold would then be coated with a layer of wax as thick as the intended bronze casting, and an inner mold would cover the wax. The united mold, upside down, would then be placed in a huge pit, with sand packed around it to support the weight and heated until all the wax melted and drained away. Then, molten bronze would be poured into the empty cavity where the wax had been and allowed to cool. When the outer mold was peeled away, the horse would be finished.

The pitfalls were tremendous. Channels had to be created to ensure all the wax drained and that no air bubbles kept the mold from filling with liquid bronze. If the mold wasn’t hot enough when the bronze was poured in, the temperature difference would crack it. In December 1493, Leonardo wrote, “I have decided that the horse should be cast without its tail, on its side.” But that meant another delay to redesign the network of channels needed for the casting. Leonardo’s notebooks are filled with drawings of molds for the horse, cranes, pulleys, and other mechanisms for hoisting the mold and its seventy-five tons of bronze.

In the end, the delays were fatal. Ludovico was under pressure; his father-in-law Ercole d’Este, the Duke of Ferrara, was angry about Ludovico’s friendship with French King Charles VIII and worried about defending Ferrara in case of a French invasion. Ludovico owed D’Este 3,000 ducats, and to pacify the duke, he offered him the bronze meant for the horse, to be cast into cannon.

The only record of Leonardo’s reaction is a half-page draft of an angry letter to Ludovico, torn vertically so that only fragments of sentences remain. Among them: “And if any other commission is to be given to me by some . . . Of the reward for my service, because I am not in a position to . . . My Lord, I know your Excellency’s mind is much occupied . . . my life in your service, holding myself always in readiness to obey . . . Of the horse I will say nothing, because I know the times . . . .”

By some accounts, five years later, the clay model was moved to a garden. Ludovico had been overthrown by his onetime French allies, and French archers occupying Milan used the horse for target practice. No trace remains.

Despite the disappointment, 1493 marked a year in which Leonardo’s studio was thrumming as he embarked on new works. His notes suggest that he had built a full-scale working model of his ornithopter on the roof of the Corte Vecchia, and he may have even tried to fly it. He was taking on a number of assignments from Ludovico - from interior decoration to creating emblems and allegorical drawings that served as a kind of propaganda for the duke, portraying him as the benevolent protector of his people.

Ludovico was still officially the regent for his nephew, Gian Galeazzo Sforza. Ludovico had married him off advantageously in 1490 to Gian Galeazzo’s cousin, Isabella of Aragon, whose father Alfonso stood to inherit the kingdom of Naples and was thus a prime ally for Ludovico.

For the wedding, Leonardo created the first of his elaborate pageants, an extravaganza depicting Il Paradiso, a representation of heaven, dramatically unveiled near midnight after a night of music, dancing, masques, and elaborate tributes to the young duke and his new duchess. As the diplomat Jacopo Trotti described it, “Il Paradiso was made in the shape of a half egg, which on the inner part was all covered with gold, with a very great number of lights, as many as stars, and with certain niches where stood all the seven planets [men dressed in appropriate costumes] . . . Around the top edge of this hemisphere were the twelve signs [of the Zodiac], with certain lights behind glass, which made a gallant and beautiful spectacle. In this Paradiso were heard many songs and many sweet and graceful sounds.”

Accounts of the event suggest that the actual pageant, with lyrics by the court poet Bellincioni, were less impressive than Leonardo’s stage setting and costumes. A year later, for the wedding of Ludovico himself to Beatrice d’Este, Leonardo created an even more dramatic show to be put on by Ludovico’s son-in-law, Captain Galeazzo Sanseverino. With a splendid golden helmet and matching shield, Sanseverino led a large band of “wild men” on horseback, dressed in animal skins and carrying clubs, accompanied by, one observer noted, “huge drums and raucous trumpets.”

Leonardo appeared to enjoy these theatrical events; he had a taste for fantasy and drama. On the street, when Leonardo saw someone interested him, he would follow that person until he knew his or her face well enough to go back to his studio and draw it – sometimes as a rough portrait, but often as a caricature or grotesque. As he once noted, he was fascinated with the “buffoonish, ridiculous, and really pitiable.”

During his years in Milan, Leonardo began his painstaking studies of light and shade, discerning seven distinct kinds of shadows and proposing to write a treatise on each one. Another manuscript from the time discusses different sources and qualities of light, with drawings showing how to depict them.

The Milan notebooks also offer practical advice to painters. To succeed, Leonardo wrote, you must “quit your home in town, and leave your family and friends, and go over the mountains and valleys into the country.” Also, portraits are best done “in dull weather, or as evening falls . . . See in the street toward evening, or when the weather is bad, how much grace and sweetness can be seen in the faces of the men and women. Therefore, O painter, use a courtyard where the walls are colored black, or with some kind of overlapping roof . . . and when it is sunny it should be covered with an awning. Alternatively work on the painting toward evening, or when it is cloudy or misty, and this will be the perfect atmosphere.”

Leonardo’s own studio was busily turning out work shot through with his influence, whether actually painted by the maestro or done by his associates and apprentices under his guidance and in his characteristic Leonardesco style. Besides the portrait of Cecilia Gallerani, there are three paintings of this period that critics attribute entirely or mostly to Leonardo.

The earliest, dating from about the same time as Cecilia’s portrait, shows a young man holding a musical score, the reason the painting is usually called “The Musician.” It is the only known Leonardo portrait of a man. His face is striking and lively under a bright red cap, standing out against the velvety dark background Leonardo advised and uniformly used in these years. In contrast, the musician’s tunic and hand seem almost sketched in; the painting is sometimes called unfinished – like the portrait of Cecilia, with her left hand shading into darkness rather than fully modeled. It seems probable that Leonardo did this deliberately to sharpen the composition and focus attention on the faces of his subjects.

The second portrait was of another lovely woman, with a bold gaze and a sensual mouth. The subject was almost surely Lucrezia Crivelli, Ludovico’s next mistress after Cecilia, who bore him another acknowledged son in 1497.

Other paintings from the Milan studio are obviously Leonardesco (strongly influenced by Leonardo’s style), with or without the maestro’s actual intervention: Boltraffio’s “Madonna and Child,” Ambrogio de Predis’ “Lady with a Pearl Necklace” (perhaps a portrait of Ludovico’s wife, Beatrice d’Este), d’Oggione’s copy of “Virgin of the Rocks.” And the fees for all these works would have followed Leonardo’s ordering, ranging from expensive to “quite cheap” depending on how much he was involved. When Boltraffio and d’Oggioni collaborated on an altarpiece of the Resurrection in the church of Milan’s San Giovanni sul Muro, the contract awarded them fifty ducats, just a quarter of what Leonardo and the de Predis brothers were promised for “Virgin of the Rocks.”

As a monument to the Sforza dynasty and a kind of family mausoleum, Ludovico was expanding and modernizing the Dominican monastery of Santa Maria delle Grazie, and soon after the great horse project failed, he commissioned Leonardo to paint a mural on the north wall of the monks’ refectory. The subject was the Cenacolo – Christ’s last supper with his disciples.

Traditionally, paintings of the last supper had shown the initiation of the covenant embodied in communion: “Eat this in remembrance of me.” But Leonardo chose the more dramatic moment when Christ announced, “Verily I say unto you, that one of you shall betray me.” “The Last Supper” shows the savior, sorrowful and resigned, at the center of the long table, with his disciples flanking him, electrified in shock and dismay. In Leonardo’s preliminary notes, he describes the painting:

“One who was drinking and has left the glass in its position and turned his head toward the speaker.

“Another twisting the fingers of his hand together, turns with stern brow to his companion, and he with his hands spread shows the palms and shrugs up his shoulders to his ears, and makes a mouth of astonishment.

“Another who has turned, holding a knife in his hand, knocks over a glass on the table . . .”

In the finished work, the details have changed. The white-bearded James is the disciple holding up his hands and shrugging; the man knocking over a glass has become Judas the betrayer, spilling a salt cellar in nervous anxiety. Philip, rising from his seat, is asking, “Master, is it I?” But the mural is precisely what Leonardo meant it to be, a stop-action point in a vivid narrative.

Both in Leonardo’s notebooks and on the monastery wall, “The Last Supper” evolved. He did it in oil and tempera rather than as a fresco, which would have required him to paint segments of the mural quickly on a fresh coat of plaster before it dried. Oil paint let him work more slowly and rethink later; subsequent restorations have revealed the way Christ’s fingers grew shorter, a dish changed position, and each of the four groupings of three disciples was subtly rebalanced.

The novelist Matteo Bandello, who as a boy watched Leonardo at work on the painting, recalled that sometimes he would paint from dawn to dusk, not even stopping to eat; at other times, he stood in front of the picture for as long as four days without touching a brush. This infuriated Bandello’s uncle, the prior, who urged Leonardo to hurry up and complained to the duke that the artist was loafing. But once, Bandello wrote, the painter was “driven by some sudden urge, at midday, when the sun was at its height, leaving the Corte Vecchia . . . to come straight to Santa Maria delle Grazie, without seeking shade, and clamber up onto the scaffolding, pick up a brush, put in one or two touches, and then go away again.”

The prior’s criticism echoes in an account of Leonardo searching through the seamiest district of Milan for a model with a face wicked enough to do justice to Judas and telling the duke, “If I cannot find one I will have to use the face of this reverend father, the prior.” Ludovico laughed loudly, Vasari wrote, and “the unfortunate prior retired in confusion to harass the laborers working in his garden.”

Sadly, the great painting was another victim of Leonardo’s restless innovation. Because of his use of oil and tempera rather than fresco technique, and perhaps because of lingering dampness in the refectory, the mural began to deteriorate and flake off the wall within a few years. By the time Vasari saw it in 1556, he described it as no more than “a muddle of blots.” Repeated efforts to restore it ruined many of Leonardo’s subtleties and hid details under layers of varnish. Then in 1796, anti-clerical French soldiers threw stones at the painting and climbed ladders to scratch out the apostles’ eyes. At one point, a door was cut through the painting, and later bricked up; it appears as the blank arch in the lower front of the mural, cutting off the view of Christ’s feet. And in 1943, Allied bombs came close to destroying the refectory and the painting with it.

Starting in 1978, a major restoration lasting twenty-one years dramatically changed the painting. Previous repaintings were peeled away, bit by microscopic bit, to try to uncover the original pigments, and many of the faces (including Judas’) became much more like Leonardo’s sketches. Only a fifth of the original paint was left. The parts of the painting that could not be saved were repainted in less vivid watercolors, giving a sense of the full composition but not hiding what wasn’t original.

The restoration was guided by a full-scale copy of “The Last Supper” painted by Gianni Pietro Rizzoli, known as Giampetrino, one of the apprentices who worked on the mural with Leonardo.

Perhaps inevitably, even this scrupulous work has been criticized as too intrusive and having lost the soul of Leonardo’s painting. But most critics say what is left reflects what he intended – and at least will not continue to deteriorate.

By this time Ludovico was Duke of Milan by title as well as force. His nephew Gian Galeazzo had died in 1494 - amid widespread suspicion that Ludovico had poisoned him - and Ludovico was proclaimed duke the next day. But Italy was in turmoil. The French king, Charles VIII, was capitalizing on rivalry among the city-states to claim weak territories. With French troops camped outside Florence, Lorenzo de’ Medici’s son and successor, Piero, had signed a treaty granting the French control of Pisa and several other towns. The outraged Florentines had overthrown the Medicis, opening the way for the charismatic Dominican friar Girolamo Savonarola to set up a puritanical theocracy featuring “bonfires of the vanities,” which were fueled by paintings, books, and anything else deemed corrupt or heretical.

Charles VIII was obviously eager to expand his realm; nevertheless, Ludovico kept up his alliance with the French king, ignoring the fact that one of the French generals, the Duc d’Orleans, was the grandson of a Visconti and thus had a claim to the dukedom of Milan.

Political machinations aside, Leonardo was established as Ludovico’s favorite artist and enjoyed his patronage; estimates of Leonardo’s annual income range from an adequate 500 ducats to a princely 2,000. But Leonardo was not above grumbling. He complained in a letter that he hadn’t received payments: “If your Lordship thought I had money, your Lordship was deceived . . . It vexes me greatly that . . . my having to earn a living has forced me to interrupt the work on “The Last Supper” and to attend to lesser matters instead of following up the work which your Lordship entrusted to me.”

When Leonardo finished the mural, Ludovico gave him three acres of land outside the city walls with a house, garden, and vineyard. It was a refuge from the heat and clamor of Milan, and Leonardo cherished it.

After “The Last Supper,” Leonardo had two years of comparative tranquility. He puttered in his garden, hobnobbed with cronies, and embarked on remodeling and redecorating the north wing of the ducal palace, which Ludovico turned into his private quarters after his duchess, Beatrice d’Este, died in childbirth. At the age of forty-five, Leonardo’s mind was as busy as ever, and a compatible mind arrived in Venice in the body of Fra Luca Pacioli, a scholar in mathematics and philosophy, who soon became Leonardo’s friend. Leonardo provided the intricate geometrical illustrations for Pacioli’s book, Divina Proportione, including a drawing of a dodecahedron with shadings that make it nearly three-dimensional.

Leonardo was also at least toying with the notion of starting his own academy, a group of intellectuals that might have included the architect Donato Bramante, the court poet Gasparè Visconti, the architect Giacomo Andrea, and the physician Giuliano da Marliano. Scholars differ on whether such an academy was actually organized, but it exists in Leonardo’s notes along with elaborate drawings of knot designs that spell out variations of “Academia Leonardo Vinci.”

This interlude for Leonardo was destined to be brief: Ludovico and the Sforza dynasty were about to be toppled. Early in 1499, the French were preparing to invade Italy. Charles VIII had died, and new King Louis XII, the former Duc d’Orleans, was determined to add Milan to his possessions. French troops crossed the border into Italy in May, and by late July, they neared Ludovico’s territory.

From his notebook, we can reconstruct a vivid picture of Leonardo preparing his studio for the arrival of looting soldiers. He counted the money in his cashbox: 1,180 lire, which he divided into packets and wrapped in paper, hiding them in nooks and crannies around the studio, and putting the small change back in the cashbox where it could easily be found. In late July, he observed another kind of preparation: “In the park of the Duke of Milan I saw a 700 pound cannon-ball shot from a height of one braccia. It bounced twenty-eight times, the length of each bounce having the same proportion to the previous one as the height of each bounce had to the next.”

Some of Ludovico’s allies were defecting, and his political foes whipped up a riot in which his treasurer was killed. On September 2, the duke fled the city, hoping for help from the Emperor Maximilian in Innsbruck. Four days later, the French took over Milan. There was no resistance.

Leonardo apparently tried to ingratiate himself with the French during the six weeks that the king stayed in Milan. He kept a coded note reminding himself to get in touch with the Comte de Ligny, whom he had met before, and another from an unidentified person urging him to “produce as soon as possible the report on conditions in Florence, especially the manner and style in which the reverend father Friar Jeronimo [Savonarola] has organized the state of Florence.”

But in December, Leonardo made plans to leave the city. The French had left, and Ludovico’s people said the duke was coming back with Swiss mercenaries and the backing of the emperor. It would hardly be prudent for a man who had collaborated with the occupiers to stick around to greet the patron he had failed to defend. His list of to-do notes, beginning with “Have two boxes made,” concludes a bit bleakly, “Sell what you cannot take with you.” So, after eighteen years and the completion of some of his greatest works, Leonardo left Milan.

Isabella d’Este wanted desperately to be Leonardo’s next patron. Her family was one of Italy’s oldest and most distinguished. Isabella was one of the three d’Este siblings whose marriages in 1491 cemented a new set of alliances in northern Italy. She began her collection with gems, intaglios, and cameos, but branched into busts and small sculptures and soon began commissioning paintings. In 1498, she had written, somewhat imperiously, to Cecilia Gallerani, asking to borrow Leonardo’s “Lady with an Ermine,” so that she could compare it with a portrait by Giovanni Bellini. (The request was a bit indelicate, since Cecilia was well-known to be the mistress of her sister’s husband.) Isabella was filling two large display rooms in her palace with her growing collection, which included two large allegories by Andrea Mantegna, two by Lorenzo Costa, and one by Perugino. But she had no paintings by Leonardo, and she badly wanted one.

Leonardo was probably accepting a standing invitation when he left Milan for Mantua in December 1499, and while he was Isabella’s guest that winter, he did a drawing of her. It shows a proud, aristocratic woman, past her prime, with the air of someone accustomed to getting her way. Shown in profile, the rendering bears a marked resemblance to a portrait of her sister Beatrice by Ambrogio de Predis.

The atmosphere in Isabella’s court may not have been entirely simpatico. Although considered intelligent, she was also strong-willed and capricious; when her lapdog died, court poets were called on to write tributes to it both in Latin and Italian. In any case, by mid-March, Leonardo was in Venice, and Lorenzo Guznago, a musician from Ferrara, visited him in his lodgings there and wrote a letter to Isabella reporting that her portrait was coming along splendidly – “very true to nature and beautifully done. It couldn’t possibly be better.”

While in Venice, Leonardo studied copperplate engraving and was busy with major works of engineering. His notes indicate that he was hired by the Venetian Senate to look into fortifying the Isonzo River, in the Friuli region northeast of the city, to ward off a Turkish invasion.

Leonardo learned of Ludovico Sforza’s last chapter in Milan. Troops loyal to the duke under Galeazzo Sanseverino had entered the city, but Ludovico’s army of Swiss mercenaries was routed, and he was captured and imprisoned. Leonardo’s note was laconic: “The duke lost his state, and his goods, and his freedom, and none of his works was completed.” It was a farewell not only to his patron, but to the great horse and “The Last Supper” as well.

In 1500, back in Florence after eighteen years, Leonardo found the city of his youth a diminished place. The theocracy of Savonarola was gone; the monk had been hanged and burned two years earlier. But Savonarola’s bonfires of the vanities had consumed Florence’s gaiety and confidence along with many of its treasures, and the Medici had yet to return; Florence was now a republic. After the French abandoned Pisa, city fathers had declared independence from Florence, and the Signoria had embarked on an unnecessary and badly waged war to regain control. Now Florence was bankrupt.

The artistic scene had changed considerably as well. Many of the older painters had died, including the Pollaiolo brothers and Domenico Ghirlandaio, but Botticelli and Lorenzo de Credi were still wielding brushes. Rising star Michelangelo Buonarroti, still only twenty-five, was in Rome, finishing his “Pieta” for St. Peter’s.

For the moment, however, Leonardo was a revered master. The fame of “The Last Supper” had preceded him, and he had no trouble finding work. The Servite friars had commissioned Filippino Lippi to do an altarpiece for the church of Santissima Annunziata, but Vasari wrote that Lippi, “like the good-hearted person he was,” stepped out of the way to let Leonardo have the job. “Then the friars, to secure Leonardo’s services, took him into their house, and met all his expenses and those of his household.”

Leonardo showed his gratitude in characteristic fashion. “He kept them waiting a long time without even starting anything,” Vasari wrote. But then, in the spring of 1501, he produced a drawing of Mary and her mother, St. Anne, with the infant Christ: the “Virgin and Child with St. Anne.” Put on display for two days, the drawing was a sensation. “This work not only won the astonished admiration of all the artists,” Vasari wrote, “it attracted . . . a crowd of men and women, young and old, who flocked there as if they were attending a great festival, to gaze in amazement at the marvels he had created.”

Fra Pietro Novellara, vicar-general of the Carmelites, wrote a description of the drawing: “An infant Christ, of about one year old, almost escaping from the arms of his mother. He has got hold of a lamb and seems to be squeezing it. The mother, almost raising herself from the lap of St. Anne, holds onto the child in order to draw him away from the lamb.”

Here, as in the “Benois Madonna,” Leonardo was prefiguring the Passion. But unlike that early work, this time, mother and child both know what the lamb means; he is embracing his fate, while she is dreading it. This scene changed repeatedly in the ten years it took Leonardo to finish it. Another drawing shows Mary on her mother’s lap holding her son, who is playing with an infant St. John. Vasari described a drawing that had St. John playing with a lamb while Christ gazed at both of them, but if that version ever existed, it has disappeared. The only indisputable fact is that it took a long time for Leonardo’s vision to fix itself – and that yet another altarpiece wouldn’t be delivered.

Though Leonardo escaped the daily urgings of Isabella d’Este, she had hardly given up on him; she wanted not only her portrait, but a larger painting for her gallery. Isabella asked the Carmelite Novellara for a report on what Leonardo was doing and whether he intended to produce something for her. In his response, he described the “St. Anne” drawing, saying it was the only work Leonardo had done since coming to Florence and added a discouraging word: “From what I understand Leonardo’s life is extremely irregular and haphazard, and he seems to live from day to day.” Apart from the drawing, Novellara wrote, Leonardo had only added a few touches to copies of his works done by his assistants. “He devotes much of his time to geometry and has no fondness at all for the paintbrush.”

In a second letter to Isabella, Novellara reported that he had talked to Salai “and some others who are close to him” and they had taken him to see Leonardo. Diplomatically, the maestro said he would like nothing more than to paint for her, and if he could escape his obligations to the King of France, he would start on Isabella’s portrait. Novellara said he had seen a painting that Leonardo was working on for one of the king’s favorites, Florimond Robertet, and described the “Madonna of the Yarnwinder.” The maestro hoped to be done with that within a month, Novellara said. “This is as much as I could get from him.”

Isabella sent a letter to Leonardo, delivered by another messenger, with no better result. Leonardo, the go-between wrote, “Sent back answer that for now he was not in a position to send another reply to Your Ladyship, but that I should advise you that he has already begun work on that which Your Ladyship wanted from him.” This evasion wasn’t much comfort, since Isabella had been told that Leonardo was working on her portrait more than a year earlier. In the end, the only service she got from him was an appraisal of some antique vases - formerly owned by the Medici family - she was thinking of buying.

“The Madonna of the Yarnwinder” was another portent of Christ’s passion. This time the infant Christ gazes rapturously at a cross-shaped gadget used for winding yarn, while his mother seems troubled. As in the “Virgin and Child with St. Anne,” both of them know – or at least have forebodings about – what the cross means.

Early in 1501, Leonardo also took a brief trip to Rome, where his friend Donato Bramante was beginning the redesign of St. Peter’s cathedral.

Still dodging his easel, Leonardo left Florence again in the summer of 1502 to serve an even craftier and more unscrupulous patron than Ludovico Sforza: Cesare Borgia, scion of Italy’s most notorious family and the model for Niccolo Machiavelli’s The Prince.

Originally known as the Borjas, the family hailed from the kingdom of Valencia in what is now Spain and came to power in 1455 when Alphonso Borgia, Bishop of Valencia, became Pope Callixtus III. He held the papacy for only three years, but that was time enough to name his nephew, Rodrigo, a cardinal. Rodrigo, in turn, became Pope Alexander VI, a brilliant but corrupt statesman who was arguably the greatest libertine in the long and colorful history of the papacy. As Florentine historian Francesco Guicciardini wrote of him, Alexander “was perhaps more evil, and more lucky, than any other pope before him . . . He had in the fullest measure all the vices of the flesh and of the spirit.”

Alexander had at least four children, three of them by his longtime mistress Vanozza de’ Cattanei, and he dedicated himself to their advancement. His oldest son, Giovanni, inherited Alexander’s former title and riches as Duke of Gandia and became commander of the papal troops, while Cesare was made Bishop of Pamplona at the age of fifteen and got his cardinal’s red hat just three years later. Daughter Lucrezia was married off three times at varying levels of nobility to enrich her and cement Alexander’s shifting alliances.

All three siblings became infamous throughout Italy. They were accused of a variety of murders, and no doubt committed at least some of them. Both Giovanni and Cesare are said to have slept with the wife of their half-brother, Gioffre, while Lucrezia was accused of incest with both Cesare and her father. When Giovanni was found floating in the Tiber with his throat cut in 1497, the investigation was abruptly terminated. Cesare was widely suspected of ordering the assassination. The accusations were never proved, but Cesare soon resigned as cardinal to assume his brother’s former title as captain-general of the church and head of the pope’s armies.

Cesare then negotiated an alliance between his father the pope and the King Louis XII of France; he married the French king’s cousin, Charlotte of Albret, and the king named him Duke of Valentinois, after which Italians called him Il Valentino. A strapping man with piercing blue eyes, Cesare was intelligent, charming, unscrupulous, and a canny military leader, whose speedy maneuvers and surprise attacks kept his enemies constantly off balance.

Leonardo had met Cesare Borgia when Cesare came to Milan with Louis XII in 1499 as Ludovico’s sometime ally. By 1502, however, the strategic situation was considerably different. Ludovico was in a French prison, and Cesare had embarked on a campaign to pacify the turbulent Romagna region north of Rome. Nominally under papal control, the Romagna was actually a patchwork of independent principalities. Beginning in 1500, with a large force of French troops and Swiss mercenaries supplied by Louis XII, Cesare rapidly subdued city after city culminating with Faenza, Florence’s trade route to the Adriatic. Then he marched on Florence, which, still trying to quell the revolt in Pisa, couldn’t resist Cesare’s troops. So the Florentines bought him off, hiring him as a condottiere – a mercenary champion – for the handsome fee of 30,000 ducats per year.

Throughout his campaign, Cesare Borgia showed no scruples. How Leonardo came to join him is not recorded. Whatever the particulars, Leonardo was with Cesare in July 1502, having made a quick reconnaissance through much of Borgia’s newly won territory, notes on terrain and fortifications.

Leonardo met the duke at Urbino, where Cesare had commandeered the luxurious palazzo of the former ally he had betrayed. When the duke left for Milan to court Louis XII, Leonardo, armed with Cesare’s passport giving him license to survey anything he wanted, toured more of his territory. According to Rafael Sabatini in his biography of Borgia, Leonardo supervised the building of a canal from Cesena to the Adriatic port of Cesenatico, drew maps of the valley of Chiana, and created a large-scale map of the rivers of central Italy featuring contour shading that conveyed a topographical sense of the terrain. When Cesare returned and resumed his campaign to subjugate the Romagna, a vivid picture of Leonardo at work was recorded by the historian Luca Pacioli: “One day Cesare Valentino, Duke of Romagna and present Lord of Piombino, found himself and his army at a river which was twenty-four paces wide, and could find no bridge, nor any material to make one except for a stack of wood all cut to a length of sixteen paces. And from this wood, using neither iron nor rope nor any other construction, his noble engineer made a bridge sufficiently strong for the army to pass over.”

Cesare set up his winter headquarters at the small fortress town of Imola. Leonardo drew a beautifully detailed and shaded map of the town, recording ground plans and measurements of the fortress, with a forty-foot moat and fifteen-foot-thick walls. Machiavelli joined the group there; as secretary of Florence’s Second Chancery, he had been assigned by the Signoria, against his wishes, to keep an eye on the duke and report on his doings.

There was plenty to report. On the day after Christmas, Machiavelli wrote: “This morning Messer Rimino was found lying in the piazza cut into two pieces; he still lies there, so that everyone has had an opportunity to see him.” Beside the body was a bloody knife and a wooden wedge used by butchers to split animal carcasses. Why Rimino was killed wasn’t clear, the envoy wrote, “except that such was the pleasure of the Prince, who shows us that he can make and unmake men according to their deserts.”

Leonardo’s notebooks during his service to Cesare Borgia are filled mainly with sketches – a bunch of grapes, a window, a drawing of the duke – and innocuous notes on the local design of carts. It is as if the usually keen observer weren’t there at all; biographer Nicholl sensed “a deep ambivalence about the nature of his employer and of the destruction and violence he was helping to spread.” If Leonardo had once been an enthusiastic designer of war machines, Cesare Borgia had taught him the reality of war – as he would later write, “the most brutal kind of madness there is.”

Cesare Borgia was at the peak of his power. The next year, his father, Pope Alexander VI, died. Cesare managed to install his own candidate as Pope Pius III, but the new pope died after only twenty-six days in office. Cesare’s enemy, Cardinal Giuliano della Rovere, promised him money and continued support in exchange for Borgia’s backing in the next conclave. The ailing Cesare accepted the offer, but after della Rovere was elected Pope Julius II, he broke his promises – a betrayal that a healthier Cesare Borgia would probably have foreseen. Another ally turned on Cesare and imprisoned him in Naples in 1504, and Julius II confiscated his lands. He escaped from a Spanish prison, but died ignominiously in 1507 in an ambush in Navarre.

Leonardo was back in Florence at the beginning of March.

Leonardo’s time in the Borgia camp hadn’t restored his taste for the paintbrush or sated his appetite for large-scale works of engineering, even if they might end in failure. For years, he had been pondering a grand scheme to make the Arno River navigable by turning it into a canal all the way from Florence to Pisa on Italy’s west coast. The Signoria recognized the benefits of this idea, especially in light of the opening of trade with the Americas, but had no appetite for its staggering cost. Now, however, there was a reason to tackle one segment of the plan: to cut off Pisa’s access to the sea.

Florence’s dispute with its former tributary had been underway for years. Pisa was well fortified and could hold out indefinitely as long as it could get supplies by way of its port at the mouth of the Arno, ten miles downstream. If the river could be diverted, Florence could retake the city by siege.

Piero Soderini was now Florence’s gonfalonier, or prime minister, with Machiavelli as his chief assistant, and both were impressed when Leonardo proposed to divert the river. In June 1503, they sent a detachment of troops to occupy a fort above Pisa; from there, Leonardo made two preliminary surveys and reported that the project was feasible.

The plan was to dig a huge ditch, a mile long and thirty-two feet deep, which would then fork into two smaller trenches to carry the river another ten miles south of its normal course to a marshland near Livorno on its way to the sea. By Leonardo’s calculations, about a million tons of earth would have to be excavated. At the bottom of the main ditch, he figured, every bucket of dirt would have to be handled by fourteen workers before it reached the top. He concluded that it would take 54,000 man-days to complete the project – unless “machines” were used to help. He had a design in his notebook for just such a mechanical digger.

Inexplicably, when the excavation began a year later, another engineer, Colombino, was in charge, and, after 80,000 man-days, the job was only in its earliest phases. Then, in October, a storm flooded the ditches, which led to the collapse of their walls. Eighty men were killed. The surrounding farms and plain were inundated, and the project was abandoned. When the Florentine troops left the scene, the citizens of Pisa filled in the ditches.

A somewhat less ambitious, but no less risky proposal by Leonardo involved building a bridge across the Golden Horn, linking the peninsular city then called Constantinople with Galata to the north. On a brief trip to Rome with Cesare Borgia in 1502, Leonardo heard the Sultan was looking for an engineer; Michelangelo, then squabbling with Pope Julius II, had expressed interest, too. Leonardo’s letter was flowery and obsequious: “I, your servant, have heard about your intention to build a bridge from Stamboul to Galata, and that you have not done it because no man can be found capable of it. I, your servant, know how . . . I will make it so that a ship can pass under it even with its sails hoisted . . . May God make you believe these words, and consider this servant of yours always at your service.”

There is no record of any reply, but Leonardo’s notebook from that time shows a working drawing of a 1,200-foot-long bridge spanning the water – exactly the width of the Golden Horn. Strikingly modern in design, the bridge would have risen to 140 feet above water level; at the time, it would have been the longest bridge in the world.

During this period in Florence, Leonardo also started work on arguably the most famous painting in the world, the “Mona Lisa,” propelled into notoriety in 1911 when it was stolen from the Louvre. The painting was recovered two years later when the thief, Italian painter Vincenzo Perugia, took it out of hiding, beneath his stove, and was arrested trying to sell it.

For centuries, a great deal of needless mystery has been generated regarding the identity of the woman who posed for “Mona Lisa.” In the simplest version, as Giorgio Vasari reported some fifty years after the fact, “For Francesco del Giocondo, Leonardo undertook to paint a portrait of his wife, Mona Lisa; he worked on it for four years and left it unfinished.” Vasari was referring Francesco del Giocondo, a prosperous silk and cloth merchant in Florence; his third wife, Lisa Gherardini, would have been about twenty-four years old in 1503, when Leonardo started work on the painting.

Speculation over the sitter’s identity was fueled by a visitor to Leonardo’s studio in 1517, who wrote that Leonardo told him it was the portrait of “a certain Florentine lady, done from life at the instigation of the late Magnifico Giuliano de’ Medici.” Giuliano was, in fact, Leonardo’s patron, but that was in Rome from 1513 to 1515. Lovers of intrigue have focused on women who might have been Giuliano’s mistresses. But Lisa Gherardini fits the bill neatly.

Like many of Leonardo’s patrons, Francesco del Giocondo never got his painting; it was still in Leonardo’s studio as late as 1517. In all likelihood, as he did with his “Virgin and Child with St. Anne,” he kept rethinking and reworking “Mona Lisa” until he was satisfied with it. A painting called La Gioconda was listed in Salai’s estate when he died in 1524; Leonardo may have left it to him – or it may have been one of Salai’s many copies of Leonardo’s works.

Leonardo and Michelangelo were the two greatest artists of the day, or perhaps any day: men of supreme talent and contrasting temperaments, sharing air and glory in the hotbed of Renaissance creativity. It was inevitable that they would become rivals.

Leonardo was older, having made his name when Michele Agnolo di Lodovico Buonarroti was a boy. By the time Leonardo returned to Florence in 1500, Michelangelo was the city’s new star. He was in Rome during Leonardo’s first months in the city. But, in the summer of 1501, Michelangelo signed a contract with the Florence Signoria to carve his great “David.”

Two years later, with the statue standing more than seventeen feet tall and comprised of some six tons of stone, Michelangelo was still liberating the figure “from the prison of the marble,” as he described it. Leonardo had begun painting Mona Lisa and had also taken on a major work for the Signoria: a fresco on the wall of Florence’s huge Council Hall of the Palazzo Vecchio, where city rulers met.

The subject of Leonardo’s mural was to be the Battle of Anghiari, a Florentine victory over Milanese troops led by the condottiere Niccolo Piccinino. In truth, the battle was a minor skirmish in which only one man died by accident when a horse fell on him. But in folklore, it was known and told as a grand clash of forty squadrons of cavalry and 2,000 troops, with St. Peter himself appearing in the heavens to urge on the Florentine warriors.

Leonardo had taken over a large unused refectory at the nearby monastery of Santa Maria Novella to use as a studio, where he would draw the enormous sketch from which the outlines of the painting would be transferred to the wall of the Council Hall. As in his work on “The Last Supper,” he had private living quarters next to the refectory. A ten-foot-wide platform was hung from a system of pulleys so that Leonardo could reach the whole surface of his drawing. By late spring of 1504, he was hard at work, his notebook filled with the snarling faces of warriors and the straining, contorted muscles of their horses. The great fresco would be no idealized triumph, but a grisly depiction of the true horrors of war.

By then, Michelangelo’s “David” – referred to merely as “the giant” by Florentines – was nearly finished. There’s no record of how the two rivals got along up to this time, but they were hardly compatible. By all accounts, Leonardo was cool, fastidious, and almost unfailingly courteous; he shunned conflict, and his rare outbursts of temper always surprised those around him. By contrast, Michelangelo was brash, a swaggerer, with a flattened nose smashed in a fistfight.

It would hardly be surprising if Leonardo resented the young genius - on top of everything else, Michelangelo’s “David” was already eclipsing the Verrocchio sculpture for which Leonardo himself had been the youthful model. So when the Signoria called together twenty-nine illustrious Florentine artists to vote on where in the Piazza della Signoria Michelangelo’s masterpiece was to be permanently displayed, Leonardo’s opinion was a bit dismissive. “I say that it should be placed in the loggia,” the record quotes him, “behind the low wall . . . in such a way that it does not interfere with the ceremonies of state.” But he was in the minority: The statue was hauled to a position of honor in the piazza, outside the main entrance of the Palazzo Vecchio, where visitors would see it before they could view Leonardo’s mural.

Whether it was before or after Leonardo’s harsh words, the rivalry produced a confrontation on the streets of Florence. Anonimo Gaddiano, who apparently heard the story from someone who was there, recorded this vivid anecdote: “Leonardo was walking with P. da Gavine through the Piazza Santa Trinita, and they passed the Pancaccia degli Spini where there was a gathering of citizens arguing over a passage of Dante; and they called out to the said Leonardo, asking him to explain the passage. At that point, by chance, Michele Agnolo was passing by, and Leonardo answered their request by saying, ‘There’s Michele Agnolo, he’ll explain it to you.’ Upon which Michele Agnolo, thinking he had said this to insult him, retorted angrily, ‘Explain it yourself – you who designed a horse to cast in bronze, and couldn’t cast it, and abandoned it out of shame.’ And so saying he turned his back on them and walked off. And Leonardo was left there, his face red because of these words.”

On another occasion, Gaddiano records, Michelangelo jeered at Leonardo, “So those stupid Milanese actually believed in you?” Not long after this, he wrote a veiled comment on Michelangelo’s characteristically tense and straining bodies in his paintings: “You should not make all the muscles of the body too conspicuous . . . If you do otherwise you will produce a sack of walnuts rather than a human figure.”

With “David” completed, the Signoria was inspired to ratchet up the rivalry between the two artists: In October 1504, Michelangelo was commissioned to paint a separate mural on the Council Chamber wall opposite Leonardo’s. He was to depict another martial scene, the Battle of Cascina, dating from an earlier war with Pisa.

It wasn’t to be. As soon as he learned of the new commission, Leonardo left Florence. His father had died in July, and his journey was in part to visit relatives in Vinci. But one biographer believes his departure was at least partly “a piqued withdrawal from the scene: a walk-out.”

Meanwhile, Michelangelo was given another large studio to produce his own drawing. He chose to paint a scene prior to the battle, showing surprised Florentine soldiers hastily putting on their armor after being caught swimming in the Arno by the enemy. As Vasari described it, “Michelangelo’s inspired hand depicted them . . . in various unusual attitudes, some upright, some kneeling or leaning forward, or halfway between one position and another, all exhibiting the most difficult foreshortenings.”

Michelangelo exhibited his finished draft in February 1505; Vasari says that “all the other artists were overcome with admiration and astonishment.” Michelangelo then left for Rome to discuss designing a tomb for Pope Julius II. A copy of his drawing remains, but there is no record that he ever started work on the painting itself.

By the time Leonardo started painting his Council Room wall, he had reached the deadline by which he had promised “without any exception or cavil whatsoever” to finish the whole project. He painted throughout the year while the Signoria paid his monthly stipend of fifteen florins. But the councilors were grumbling, and Vasari recorded a telling incident: “It is said that when [Leonardo] went to the bank for the salary which he was accustomed to receive from Piero Soderini every month, the cashier wanted to give it to him in piles of quattrini [small coins]. He did not want to take them, saying, ‘I am not a penny painter!’ There were complaints about this behavior, and Piero Soderini was turning against him. So Leonardo got many friends of his to gather up a whole pile of quattrini, and he took them to him to return the money; but Piero did not want to accept them.” The payments to Leonardo continued through the end of October.

Some records suggest that the painting ran into technical problems akin to those of “The Last Supper.” Writer Antonio Billi said Leonardo’s pigments weren’t adhering to the wall because he had been fobbed off with adulterated linseed oil. Whatever the cause, Leonardo never finished the mural, though a large central portion was near completion when he left Florence in May 1506. As late as 1549, writer Anton Francesco Doni wrote to a friend, “Go up the stairs of the Sala Grande, and take a close look at a group of horses and men, a battle-study by Leonardo da Vinci, and you will see something miraculous.” But twelve years later the painting was gone, covered by a huge multi-wall fresco done by Giorgio Vasari.

Unless the painting had deteriorated, Vasari would likely have taken steps to preserve a work of Leonardo’s before plastering the wall for his own fresco. In fact, a tiny inscription in a corner of Vasari’s painting reads Cerca Trova, seek and ye shall find. In recent years, various high-tech means have been used to probe the walls for a buried painting. But the results have been ambiguous, and it isn’t even certain which wall of the chamber Leonardo painted. Even if Vasari’s fresco were ripped away, there might be nothing but fragments left of “The Battle of Anghiari.” And as a Florentine councilor recently argued, “Vasari may not be Leonardo, but he is still Vasari.”

Leonardo’s initial drawing for the painting has also vanished. There are several copies of varying quality, but the closest we are likely to get to Leonardo’s work is a marvelous watercolor attributed to Peter Paul Rubens. Rubens never saw the original mural, but his version was painted sometime after 1600 directly on top of an earlier Italian drawing of the fresco. Rubens conveys all the fury, turmoil, and brutality of Leonardo’s preparatory sketches.

Leonardo turned to classical themes during his second stay in Florence, creating a drawing of Neptune in his chariot for his patron Antonio Segni, a Florentine banker. He seems to have painted a Bacchus as well; Alfonso d’Este, Isabella’s brother and the Duke of Ferrara, wrote to one of his business agents that he wanted to buy Leonardo’s “Bacchus,” but the agent replied that the painting had already been promised to the Cardinal of Rouen. If the painting did exist, it has been lost.

Leonardo’s classical period neared its peak in “Leda and the Swan,” a painting that Antonio Segni may have commissioned and Leonardo may or may not have finished. Several drawings in Leonardo’s hand exist, along with copies of several versions of the painting, apparently by Leonardo’s apprentices. The French royal collection once included a “Leda” attributed to Leonardo, but it was dropped from the list late in the seventeenth century. It has long been rumored that Madame de Maintenon, mistress and secret wife of King Louis XIV, found the painting immoral and ordered its removal.

She would have had reason. The painting depicts the classical myth of Jupiter, disguised as a swan, courting the lovely princess Leda. None of Leonardo’s sketches of the scene are as erotic as earlier interpretations of the scene by other artists, which show the swan forcing itself upon Leda; his versions stress fecundity and fertility, portraying Leda as a Rubensesque beauty with a brood of small children hatching from eggs at her feet. In Leonardo’s most striking drawing, Leda rests on one knee, with the other leg poised to lift her to her feet, while the amorous swan seems to be nibbling at her ear. Finished copies of the painting show Leda standing on both feet, and there is also a full-scale copy of a preliminary drawing of the standing Leda done by Raphael while he was in Florence in 1505 or 1506. Of the painting itself, if it existed, there is no trace.

But more than one swan inhabited Leonardo’s thoughts in those years. He had returned to his obsession with flying and flying machines, sketching detailed designs for such parts as rotating wing joints, and musing repeatedly on what it would be like to soar through the air. A small notebook now in the Royal Library in Turin is filled with these notes, drawings of bird flight, and observations on aerodynamics.

“A bird is a machine working within mechanical laws,” Leonardo wrote. “It lies within the power of man to reproduce this machine with all its motions, but not with as much power.” A machine built to fly would lack only “the spirit of the bird,” he said, which the spirit of man would have to supply. In his own spirit, he was already in the sky, mounting thermals with his wings steady or banking with the wind: “If the north wind is blowing and you are gliding above the wind, and if in your straight ascent upward that wind is threatening to overturn you, then you are free to bend your right or left wing, and with the inside wing lowered you will continue a curving motion . . .”

He may actually have tried his flying machine. The Turin notebook contains two versions of what amounts to a press release, an announcement worthy of P.T. Barnum: “The big bird will take its first flight above the back of the Great Cecero, filling the universe with amazement, filling all the chronicles with its fame, and bringing eternal glory to the nest where it was born.” The “great Cecero” is Leonardo’s version of Monte Ceceri, a peak near Florence; no doubt he spelled it Cecero because that is Florentine dialect for swan.

For all the notebook braggadocio, if he did try to fly, it must have been in secret. If there had been any such public event, it is hard to imagine that it was never recorded, by Leonardo or anyone else. The only surviving note is a tantalizing sentence by the mathematician Girolamo Cardano, who wrote in 1550 that Leonardo was an “extraordinary man” who tried to fly “and was frustrated.” Leonardo would surely have left word of such an experiment, whether it was a success or a failure; he would have learned too much from either to let it pass. In all probability, he spread his wings only in his imagination.

By 1506, Leonardo had become a trophy, sought after by cities, nobles, and kings who squabbled over his talents, his attention, and his very presence.

Milan was calling him back, primarily to settle the long legal battle over payment for the “Virgin of the Rocks,” but Florence didn’t want him to leave, especially without finishing “The Battle of Anghiari.” In May, the Signori reluctantly permitted him to go to Milan if he promised to return in three months, with a penalty of 150 florins if he stayed longer – guaranteed by the manager of the bank where he kept his savings.

Milan now had a French governor, Charles d’Amboise, an intelligent, vigorous and self-indulgent young aristocrat – “as fond of Venus as of Bacchus,” one historian wrote – who was already a fan of Leonardo. He took him into his castle, the former Sforza stronghold, and Leonardo almost immediately began making detailed plans for a summer villa d’Amboise intended to build outside the city. He visualized the landscaping in exquisite detail, including orange and lemon trees, an arbor covered with a net of copper wire to keep songbirds inside, and a mock windmill powered by water to act as a fan on warm days.

The two men became as close as a master and servant can be. “We loved him before meeting him in person,” d’Amboise was to write, “and now that we have been in his company . . . we see in truth that his name, though already famous for his painting, has not received sufficient praise for the many other gifts he possesses, which are of an extraordinary power.” To mark Leonardo’s fifty-fifth birthday, the count gave him back his vineyard, which the French had confiscated soon after they took over Milan in 1500.

As Leonardo’s deadline for returning to Florence approached, d’Amboise wrote the Signoria asking for permission for Leonardo to extend his stay until the end of September to “supply certain works which he has at our request begun.” The Signoria agreed, not wanting to offend Florence’s powerful but touchy French allies. Early in October, however, with the painter still in Milan, Soderini wrote d’Amboise angrily pointing out that Leonardo “has not behaved as he should have done toward the republic, because he has taken a large amount of money and made only a small beginning on the great work he was commissioned to carry out. . . . We do not wish any further requests to be made on this matter.”

Early in December, d’Amboise wrote again, saying he would not seek any further extension but asking that Florence treat Leonardo with the respect and honors he deserved. Then, however, Soderini’s ace was trumped: His ambassador to France reported that Louis XII wanted Leonardo to stay in Milan until the king himself arrived there on a planned visit, because the king wanted “certain little pictures of Our Lady, and other things as they occur to my fantasy, and perhaps I will get him to paint my own portrait.” Soon, Soderini received the king’s own confirmation: “We have necessary need of Master Leonardo da Vinci, painter of your city of Florence.”

On an earlier visit to Milan, King Louis had been powerfully taken by “The Last Supper,” even exploring the possibility of removing the fresco from its wall and hauling it back to France. Then his courtier Florimond Robertet had shown him the “Madonna of the Yarnwinder,” and the king’s appetite for Da Vinci paintings became voracious.

There’s no record of any immediate commission for Leonardo after King Louis arrived in Milan at the end of April 1507, but the king did provide him some added income: the tolls from a section of Milan’s system of canals. The demand for Leonardo’s services had not subsided – Isabella d’Este was still writing imploring letters, and Soderini was still fuming in Florence – but the king’s whim was law, and there was no immediate need for Leonardo to leave Milan.

Legal wrangling over the “Virgin of the Rocks” would drag on for years. By this time, the dispute was about the second version of the painting, done mostly by Ambrogio de Predis after Ludovico Sforza sent the first one to Emperor Maximilian; the new painting was to replace the original in the chapel of the Confraternity of the Immaculate Conception.

The second painting was, in fact, delivered to the Confraternity sometime after 1499, but Ambrogio complained to King Louis in 1503 that the friars still owed money for it. The king sent the case to arbitration, and after three years the ruling went against the artists: The painting was imperfetto, meaning either incomplete or not good enough - perhaps simply that Leonardo’s hand wasn’t sufficiently evident. In either case, Leonardo was ordered back to Milan to finish it.

The judgment awarded the painters 200 lire on completion - less than they wanted, but twice what the friars had offered - and the Confraternity came up with half this amount in August 1507. But that didn’t end the dispute. The retouched painting was delivered early in 1508, but in August of that year, a new contract was drawn up: Instead of the final payment of a hundred lire, the painters would get the right to do yet another copy of the painting and sell it. Ambrogio was to do the painting under Leonardo’s supervision, and the two men would share equally in whatever price it brought. If this third “Virgin of the Rocks” was ever painted, it has vanished.

Another legal dispute finally took Leonardo back to Florence – a bitter fight with his half-brothers over the will of his uncle, Francesco.

When Leonardo’s father, Ser Piero da Vinci, died in 1504, Leonardo was passed over in his will. There may have been tensions simmering between father and son, or because Leonardo was by then a successful artist, with a growing retinue of apprentices and servants, he had less claim to Piero’s money than his eleven legitimate children. In either case, there is no record that Leonardo challenged Piero’s will.

But the omission evidently rankled Piero’s younger brother. Francesco had been Leonardo’s boyhood mentor on those long walks through the Tuscan countryside, and after Piero’s death, his brother drew up a new will naming Leonardo as his only heir. This reneged on an earlier agreement between the brothers that Francesco’s estate should go to Piero’s legitimate children, and when Francesco died, they moved immediately to have his will invalidated.

Leonardo took a large part of his household back to Florence to fight the case. It rapidly grew as rancorous as family fights get; Leonardo wrote that his brothers treated him “not as a brother but as a complete stranger” and that they had “wished the utmost evil” to Francesco while he was alive.

Leonardo brought some powerful guns to bear. Even before he arrived in Florence, the Signoria had a letter from King Louis asking for direct intervention in the case on behalf of “our painter and engineer in ordinary,” Leonardo’s official title. Another letter from Charles d’Amboise asked the council to expedite the legal matter as swiftly as possible. And a letter from Leonardo to Cardinal Ippolito d’Este, another of Isabella’s brothers, asked him to intervene with Ser Raffaello Hieronomo, a member of the Signoria who was adjudicating the case.

There is no record of how the dispute was resolved, but it was still dragging on in mid-1508, when Leonardo was back in Milan. But six years later, when his brother Giuliano was in Rome needing help to claim a benefice, Leonardo tried to provide it; and a cordial letter from Giuliano’s wife conveying greetings to Leonardo was among Leonardo’s papers when he died. Whatever the outcome, the bitter family feud ended in reconciliation.

In the Milanese court of Charles d’Amboise, Leonardo resumed another role of the Sforza years: the showman-in-chief, stager of public celebrations, masques, and entertainments for the count and his retainers. He began with a grand welcome for Louis XII, with arches of greenery over the streets from the Duomo to the castle, a triumphal chariot carrying actors depicting the cardinal virtues, the arms of France and Brittany prominently displayed, and the god Mars “holding in one hand an arrow in the other a palm.”

King Louis was welcomed again the next year when he returned to Milan after routing the Venetians at the Battle of Agnadello. This festa included an allegorical battle between a dragon, representing France, and the lion of Venice. Leonardo’s stage, set for a production of the operetta Orfeo, dramatizing Orpheus’ trip to the underworld to rescue his wife Eurydice, had a mountain that opened (by means of pulleys and counterweights) to show Pluto at home in hell, complete with devils, furies, and in Leonardo’s notes, “many naked children weeping.” There were appropriate musical themes for the characters: trombones for Pluto, treble viols for Eurydice, contrabass viols for Orpheus, and guitars for Charon, ferryman on the River Styx.

While he was in Florence battling his brothers, Leonardo picked up the anatomical studies he had begun there years earlier. He was staying with linguist and mathematician, Piero de Braccio Martelli, also an intellectual and patron of the arts, and Leonardo used the long intervals between formal court proceedings to hobnob with other artists, to reshuffle his notes en route to a final organization of his papers that never materialized, and to perform dissections, both on animals and human corpses.

By this time, Leonardo wrote, he had dissected “more than ten human bodies.” But in late 1507 or early 1508, he witnessed a strangely peaceful death: “This old man, a few hours before his death, told me he had lived for more than a hundred years and that he was conscious of no deficiency in his person other than feebleness. And thus, sitting on a bed in the hospital of Santa Maria Nuova in Florence, without any movement or sign of distress, he passed from this life. And I made an anatomy to see the cause of a death so sweet.”

He was especially interested in the vascular system, and he boasted about his skill in exposing its intricacies: He had stripped away “in the most minute particles all the flesh that lies around these veins, without causing any flow of blood save a scarcely perceptible bleeding of the capillary veins.” He discovered that the old man’s arteries were “very dry, thin and withered,” and “in addition to the thickening of their walls, these vessels grow in length and twist themselves in the manner of a snake.” The old man’s death, he concluded, came from “weakness caused by a lack of blood to the artery which feeds the heart and lower members.” He found that the liver was deprived of blood and “desiccated, like congealed bran in color and substance,” while “the skin is almost completely deprived of nourishment” and therefore “the color of wood, or dried chestnuts.” Leonardo followed that dissection with one of the body of a two-year-old boy, “in which I found everything to be the opposite to that of the old man.”

Leonardo’s drawings from this period are wonderfully detailed and shaded, showing three-dimensional layerings of muscles, bones, and tendons. He drew male and female genitalia and a standing woman showing her uterus in early pregnancy. He left studies of the lungs and abdominal organs of a pig and the placenta and uterus of a cow, with a small fetus inside. And he described the grisly work of dissection without refrigeration, telling the reader: “You will perhaps be deterred by the rising of your stomach.” One body wouldn’t last long enough for a thorough exploration of the vascular system, he noted, so “it was necessary to use several bodies in succession . . . I repeated this process twice, in order to observe the variations.”

Two years later, Leonardo traveled twenty miles south of Milan to Pavia, where he spent several months listening to Marcantonio della Torre’s lectures on anatomy. “Messer Marcantonio,” as Leonardo called him, was a young man, but an acknowledged master of the skill, and Leonardo made swift drawings as the professor lectured and his assistants carved the bodies in the anatomy theater of Pavia’s famous university.

Della Torre and Leonardo were kindred spirits, both seeking the deepest possible knowledge of the body and all its works. They equally detested “abbreviators,” their term for ostensible scholars who simply rehashed the work of others in digested form. “The abbreviators of works insult both knowledge and love,” Leonardo wrote, “seeing that the love of something is the offspring of knowledge of it . . . Impatience, the mother of stupidity, praises brevity, as if we did not have a whole lifetime in which to acquire complete knowledge of a single subject, such as the human body.”

Leonardo was working in his studio during his second Milan period with varying degrees of urgency. He was soon done with retouching the “Virgin of the Rocks” and went to work for Louis XII; in a letter Leonardo mentions “two Madonnas of different sizes done for our most Christian king,” which have been lost. He still had his “Mona Lisa” in the studio, and was probably reworking and retouching it whenever he felt moved to do so. In 1508, he drew several studies of lips, including the unmistakable half-smile that appears in the painting; it’s likely that this defining feature of “La Gioconda” first appeared then, too. Leonardo and his assistants were working on several versions of “Leda” during this period as well; one finished painting by Leonardo’s talented associate Giampetrino (Gianni Pietro Rizzoli) probably dates from 1510 or 1511 and shows Leda on one knee, surrounded by four babies and broken eggshells - but without the swan.

In Milan, Leonardo’s concept of the “Virgin and Child with St. Anne” continued to evolve. The great cartoon now in London’s National Gallery dates from 1508, and in this version Mary, on her mother’s lap, is holding the infant Christ, who is blessing a slightly older John the Baptist. But this cartoon was apparently never used for a painting. An oil painting, now in the Louvre and generally regarded as less powerful than the cartoon, reverts to Leonardo’s original concept, showing Christ reaching for a lamb but without John the Baptist. The painting was probably done around 1510 and was still in Leonardo’s studio in 1517. Part of a study for this painting has been detected beneath the surface of the Giampetrino “Leda.”

For a while, another great equestrian statue was in the works - for the tomb of the condottiere Gian Trivulzio, who had made himself Marshal of Milan. Trivulzio set aside 4,000 ducats for this grandiose monument, and Leonardo drew many studies for it and roughly estimated what it would cost to sculpt and cast. The horse and its armored rider were to be prancing atop a huge carved marble arch, adding considerably to the cost, but even so Leonardo’s estimate came in at less than 3,000 ducats, leaving a hefty profit margin. Leonardo’s sketches are magisterial: dynamic and lifelike chargers ready to burst into action. But the project never materialized - for Leonardo or any other sculptor. The tomb remained Trivulzio’s fantasy.

There is evidence, albeit meager, that around age fifty-five, Leonardo had sex with a woman. In the early nineteenth century, artist, critic, and Leonardo aficionado Giuseppe Bossi baldly asserted that there had been such a relationship. Arguing that an artist must experience a passion in order to depict it, Bossi wrote: “That Leonardo . . . loved the pleasures of life is proved by a note of his concerning a courtesan called Cremona, a note which was communicated to me by an authoritative source. Nor would it have been possible for him to have understood human nature so deeply, in order to represent it, without becoming, through long practice in it, somewhat tinged with human weakness.”

If Leonardo wrote a note about such a woman, it has been lost, and Bossi said nothing more about his “authoritative source.” The only other hint of La Cremona’s existence is a list, in Leonardo’s writing, of his companions on a journey, possibly the trip to Pavia in late 1509 to hear Marcantonio della Torre’s anatomical lectures. Besides identifiable associates including Salai, there is a “chermonese,” Leonardo’s spelling for Cremonese, a native of Cremona. At about the same time, a distinctive new face appears in Leonardo’s studies for the head of Leda and for a series of drawings, reminiscent of the “Mona Lisa,” known as the “Nude Gioconda.” The model for these drawings - in a pose similar to Lisa’s - is nude to the waist.

As evidence, this is circumstantial at best. But it is plausible that Leonardo, with his passion for firsthand knowledge of everything from grinding pigments to dissecting corpses, would be curious about heterosexual love. In his notes, he muses about a spontaneous triggering of desire that appears to refer to a woman.

Meanwhile, the tide of war was on the rise again in northern Italy. Pope Julius II had now turned against his French allies, decreeing that they must be driven out of the country. By the end of 1511, the pope’s Swiss mercenaries were threatening Milan. In April 1512, the French won a tenuous victory at Ravenna, but by year’s end, they had abandoned Milan to Ludovico Sforza’s son Massimiliano and the forces of the Hapsburg emperor Maximilian, who was in league with the pope.

Still wary of how the returning Sforza might reward his apostasy to Ludovico, Leonardo made himself scarce. He was still on the French king’s payroll, but his patron Charles d’Amboise had died and his purse was a good deal thinner. Now, however, he was safe with friends at the comfortable country house of soldier and engineer Girolamo Melzi on a bend of the Adda River near the village of Vaprio. In truth, he was only twenty miles from Milan, but that was far enough.

Melzi was the father of one of Leonardo’s pupils, Francesco Melzi, nicknamed Cecco, who had joined the studio in 1507 and quickly made himself indispensable. He was to become a fine draftsman and painter (he drew a lovely red chalk drawing of Leonardo at about sixty years old), but he functioned primarily as Leonardo’s secretary and scribe. His elegant handwriting appears throughout Leonardo’s notes, copying faded or illegible writing, providing captions and footnotes, and taking dictation from the master. Melzi, an educated aristocrat, had the manners and breeding that Salai so clearly lacked. Leonardo was fond of him, but the relationship was probably not homosexual; in later life, Melzi married one of the most beautiful women in Milan, who bore him eight children.

After Leonardo’s death in 1519, Francesco Melzi became his literary executor, collecting and preserving Leonardo’s papers and generally preserving the flame. Melzi assembled and published the great Treatise on Painting that Leonardo promised during his lifetime but never got around to. As we have seen, a good many of Leonardo’s paintings and papers have not survived him, but without Melzi, much more would have been lost.

In retreat at the Villa Melzi in 1512 and early 1513, Leonardo resumed his lifelong study of water, sketching eddies, currents, and complex swirls resembling braided hair. He did a series of anatomical studies, some apparently worked up from sketches made during the Pavia lectures and others from animal dissections done at the villa. There is a self-portrait of the artist at sixty, a drawing that critic Kenneth Clark called not so much a portrait as a self-caricature exaggerating the ruefulness and decrepitude that Leonardo felt on passing another decade. He drew himself sitting with crossed legs, chin resting on a long staff, his beard white, one hand to his forehead, with hooded eyes gazing wistfully into the distance. Cecco Melzi’s red chalk drawing, probably done about the same time, shows a man still handsome and vigorous with an unlined face, steady eyes and a firm mouth. Even allowing for Melzi’s affection for Leonardo, it is probably the better likeness.

Leonardo was in dire need of a patron. French governor of Milan Charles d’Amboise, his friend and benefactor, was dead. King Louis XII was preoccupied with war. Leonardo had sounded out Sforza loyalists as to how the new duke, Massimiliano Sforza, might receive a painter who had served his father’s enemies, but the signs weren’t encouraging. So in the summer of 1513, when he received an invitation from Giuliano de’ Medici to come to Rome and live under his protection, it was a Godsend.

Giuliano and his brother Giovanni, the surviving sons of Lorenzo the Magnificent, had lived in exile in Urbino and Mantua during the turbulent years of Savonarola’s reign and the subsequent Florentine republic. But in the summer of 1512, they staged a bloodless coup to overthrow the republic and regain their heritage. As Gonfalonier Soderini left town by one gate on his way to exile, Giuliano de’ Medici entered by another. His elder brother Giovanni followed with 1,500 soldiers, and Medici’s rule resumed with quiet efficiency. There were no executions; members of the Signoria kept their palazzi; no one went to jail.

The corpulent, shrewd Giovanni was a natural leader and a talented administrator. He was also a powerful cardinal on his way to becoming pope, and when he became Pope Leo X in March 1513, he decided that his brother, a charming but hardly forceful man in frail health, wasn’t up to ruling Florence. So he gave that job to their cousin Lorenzo di Piero de’ Medici and took Giuliano to Rome, where Giuliano - festooned with the titles Prince of Modena, Piacenza, and Parma - was given command of the papal armies. He made little impact on the troops, but he was universally liked and admired for his scholarship, courtesy, and taste. He also carried on the Medici heritage as a patron of the arts. Historian Benedetto Varchi wrote that Giuliano treated Leonardo “more like a brother than a friend.”

It’s unclear when Leonardo met Giuliano de’ Medici or how well they knew each other. It is possible that they first met in Venice in 1500, and Giuliano had surely seen some of Leonardo’s work, including “The Last Supper” and perhaps the splendid central portion of the “Battle of Anghiari” and the unfinished portrait of Isabella d’Este. When Leonardo and his household arrived in Rome in October 1513, Giuliano assigned architects to alter a suite of apartments for the artist in the Villa Belvedere, the pope’s summer palace.

Rome was then a city of 50,000, considerably smaller than Milan, but notorious for the corruption of the papal court and the licentiousness of the clergy. There were plenty of artists in residence, many of them well known to Leonardo, including Bramante, Michelangelo, Raphael, and Leonardo’s former pupil Atalante Migliorotti, but Leonardo’s notebooks contain no record of his friends or of his social life during his two years there.

His notebooks do contain various other correspondence. There are drafts of letters Leonardo wrote trying to persuade papal officials to cough up the benefice owed to his half-brother Giuliano, with whom he was now reconciled. There is also a letter to Giuliano da Vinci from his wife, Alessandra, which Giuliano evidently gave Leonardo because of a line in it: “I forgot to ask you to remember me to your brother Leonardo, a most excellent and singular man.” And there is a grumpy letter from Leonardo to Giuliano de’ Medici, complaining of an ungrateful, unruly, and deceitful German assistant, Giorgio, who had been subverted by another German, Johann the mirror-maker. Leonardo wrote that Johann, jealous of Leonardo’s influence with Giuliano, had talked Giorgio into abandoning the workshop Leonardo had given him and had taken it over for his own mirror works.

Leonardo was exploring what would now be called solar power, the use of parabolic mirrors to focus the sun’s rays; he was struck by the fact that a mirror can reflect heat without absorbing it. He was also busy dissecting corpses again, probably at the hospital of Santo Spirito. Here again, he complained that the spiteful Johann had “hindered me in anatomy, denouncing it before the Pope and also at the Hospital.” Nonetheless, some of Leonardo’s most notable anatomical drawings – especially his studies of fetuses in the womb – date from this period.

The notebooks record the ever-questing scope of Leonardo’s mind. He spent hours over geometric equations and drew long series of “lunes,” figures containing variable spaces formed by intersecting arcs of circles. He experimented in acoustics and hunted for fossils; he recorded bits of his household expenses in the coinage of Rome: “Salai: 20 giuli; for the house: 12 giuli.” His obsession with water continued in half a dozen texts pondering “The Deluge,” which he may have meant to be part of the great treatise on painting that he never wrote or as preparation for actually painting a great flood. “Broken trees loaded with people,” he wrote. “Ships broken in pieces, smashed against rocks. Flocks of sheep; hailstones, thunderbolts, whirlwinds. . . . Hills covered with men, women and animals, and lightning from the clouds illuminating everything.”

With these musings, he left a series of ten drawings in black chalk, depicting the grand sweep and ferocious details of a great flood of water – torrents, erupting waves, vortices and tunnels of water, giant waterspouts, devouring whirlpools, the shattering impact of monstrous waves. Together, the drawings are a tour de force, an effort both to understand and to depict the full fury of nature. Such a painting would have been an even more ambitious project than his attempt to show the horror of war in the Battle of Anghiari.

But the aging Leonardo - his beard turning white and his eyes needing spectacles – didn’t paint it. In a letter to Giuliano de’ Medici, who was suffering from consumption, he mentioned an unspecified “malady” that may have been a minor stroke; a visitor in 1517 noted that Leonardo’s right hand was paralyzed. That wouldn’t have hindered the left-handed Leonardo in drawing and painting, but it might well have slowed him down and ruled out any major new projects.

He did complete two paintings in Rome – probably the last of his career. Both, now in the Louvre, depicted a young, somewhat androgynous John the Baptist. In one, usually called “St. John in the Desert,” he is sitting under a tree in a wild place, his right arm crossed over his chest with the forefinger extended. In details that may have been added to the painting long after Leonardo’s death, St. John is wearing a panther-skin loincloth and a crown of grape leaves, leading some critics to call the picture “St. John with the Attributes of Bacchus.” The other painting, more powerful but uneasily ambiguous, shows the naked torso of the saint against a dark background, again with his right arm crossed over his chest, but now with the forefinger pointed to the sky. The faces in both paintings show the same features, but the half-length St. John has a subtle smile as mysterious as Mona Lisa’s. This painting may well have been commissioned by Pope Leo; the pope did order a work by Leonardo. But when he heard that the artist was distilling oils for the varnish he would use on the painting, the pope complained, “Alas, this man will never do anything, because he starts to think of the end before he has even begun the work.”

The pose of the half-length “St. John” may have evolved from a sketch of an announcing angel – Gabriel – dating from about 1505, with the right arm pointing to the sky and the left touching the chest. The sketch may have been done by Salai, but the position of the pointing arm was corrected in Leonardo’s hand. But the evolution of the drawing was not filled out until 1991, when another sketch turned up in a private collection – the notorious drawing now known as the “Angelo Incarnato,” or angel made flesh.

In this version, the right arm is still upright, but the left hand, with feminine grace, holds a veil of filmy fabric against the chest, and below, a large erection clearly appears through the veil (though someone has smudged it slightly, apparently trying to erase it). The figure has the head and face given to St. John in both paintings, but the expression has been transformed: The cheeks are gaunter, suggesting illness; the eyes are large and pleading; the smile is a sly invitation. In this context, the arm is no longer announcing but beckoning. The drawing is disturbing, verging on pornography.

The finished painting of the half-length St. John has none of this lurid quality. The right arm has been crossed over the chest, half hiding the overly graceful fingers of the left hand; the face glows, softened and deepened by fine layers of the varnish that vexed the pope. But the androgyny and mystery of the painting remain – and the effect is highlighted by the uneasy knowledge of the Angelo Incarnato.

Leonardo was part of the pope’s entourage when Leo traveled to Bologna and Florence in October 1515 to meet the new French king. Only twenty-one years old, Francis had taken the throne when Louis XII, his cousin and father-in-law, died without a male heir, and Francis had recently proved himself by defeating the Sforzas’ Swiss mercenaries in the Battle of Marignano. The new king had long admired his father-in-law’s paintings by Leonardo and had seen “The Last Supper.” In addition, he had been presented with a mechanical lion constructed by Leonardo when Francis met Giuliano de’ Medici the previous July.

There is no record of their first meeting or any trace of a royal invitation to Leonardo. But in the late summer or early fall of 1516, about six months after his patron Giuliano de’ Medici died of consumption, Leonardo and his entourage left Rome on the long journey to Francis’ court at Amboise, in the valley of the Loire. They probably stopped over in Milan, where Salai stayed for a while in Leonardo’s garden; Salai would rejoin the household only from time to time after that. In Amboise, the king gave Leonardo a home, an elegant manor-house half a mile from the royal residence, together with a generous pension. From then on, Leonardo was to be formally titled the paintre du Roi. He was also to be the king’s friend.

Francis was a tall, vigorous man, with a wide-ranging curiosity and an enormous nose. He was also charming, with a reputation as a ladies’ man. The Italian traveler Antonio de Beatis wrote that Francis “is lascivious and enjoys entering the gardens of others to drink different waters.” Francis was overwhelmed by Leonardo, and not only for his artistic talents. Benvenuto Cellini, who worked for Francis years later, wrote that the king “was completely besotted” with Leonardo’s mind “and took such pleasure in hearing him discourse that there were few days in the year when he was parted from him, which was one of the reasons why Leonardo did not manage to pursue to the end his miraculous studies.” Cellini said Francis told him “he could never believe there was another man born in this world who knew as much as Leonardo, and not only of sculpture, painting and architecture, and that he was truly a great philosopher.”

Now sixty-five, Leonardo was looking and feeling older; the great self-portrait now in the Biblioteca Reale in Turin shows him white-haired and stooped, with a deeply lined face and a thousand-yard stare, but still alert and on the lookout for a new idea. He spent much of his time rearranging his papers and making geometrical studies and sketches of moving water. Occasionally, he would still draw a striking face or a floor plan. But in 1517, he told the visiting Antonio de Beatis that he had stopped painting. (It was Beatis, traveling with Cardinal Luigi of Aragon, who recorded Leonardo’s story of the “Mona Lisa” being commissioned by Giuliano de’ Medici.)

Leonardo did launch a major project for the king: plans for a huge new palace complex at Romorantin, some thirty miles to the east of Amboise, and a network of canals to be built between the Loire and the Saone. None of this got built, but Leonardo’s drawings of the palace resembled the “ideal city” he first visualized in Milan thirty years before.

He also had a fresh, enthusiastic audience for his talents as an impresario, and he provided a series of tableaus, masques, and pageants for Francis and his court. Back in Mantua, Isabella d’Este still kept tabs on Leonardo, and she got a lavish description of the triumphal arch he set up for a double feast marking the baptism of the king’s first son and the wedding of the royal niece to Lorenzo di Piero de’ Medici, now Duke of Florence. For a pageant honoring Francis’ victory at the Battle of Marignano, Leonardo rigged huge mortars to fire inflated balloons that drifted down on the entranced audience and bounced merrily on the ground. In 1518, Leonardo threw a party of his own for the king in the gardens of his manor house, with a vast canopy of blue cloth spangled with golden stars hanging over the royal dais. The show repeated the Paradiso Leonardo had first conjured up in 1490, with actors representing the planets and hundreds of torches blazing.

We will leave him there, master of the revels, pleased with the impact of his pageant and the delight of his royal guest. Leonardo lived for another year, apparently in failing health; he drew up his will in April 1519, leaving his papers to the faithful Melzi, his Milanese garden to Salai, a fur-lined cloak to his housekeeper, and a remembrance for his half-brothers in Florence.

Leonardo da Vinci died on May 2, 1519, sixty-seven years old. According to Vasari, King Francis held his dying friend in his arms and propped up his head in the final moments, a scene portrayed in two romanticized nineteenth-century French paintings. But considering that a royal proclamation was issued in a town two days’ ride from Amboise at the time of Leonardo’s death, it is unlikely that the king was at his friend’s bedside in his final hours. Leonardo himself would have insisted on an unflinching examination to find the truth. Lesser mortals may decide that if the story wasn’t true, it should have been.

That’s a suitably enigmatic note to close out the life of a man who will be forever at least a little opaque to the rest of us. For all his achievements, he was a private man who never tried to explain the workings of his mind or his core beliefs. How do we reconcile the painter of all those saints, angels, and Madonnas with the flinty rationalist who sought only the truth, no matter what dogmas were shattered in the process? Vasari observed that Leonardo “had a very heretical state of mind. He could not be content with any sort of religion at all, considering himself in all things much more a philosopher than a Christian.” And, in fact, the defining feature of Leonardo’s religious paintings is not their spiritual quality, but their spontaneity and human appeal - from “The Benois Madonna” playing with her baby to the homoeroticism of “St. John.”

As a homosexual, Leonardo lived his whole life outside his society’s conventions of morality and religion and learned not to talk about it. But what he did say was heretical enough. The human soul, he once wrote, “desires to remain with its body,” and “takes its leave of the body very unwillingly . . . because without that body it can do nothing and feel nothing.” Death is “the supreme hurt, which kills the memory together with life.” These are not the musings of a man looking forward to an eternal afterlife.

Being gay was hardly a casual lifestyle choice. Homosexual acts were theoretically (and occasionally in practice) capital crimes, punishable by burning at the stake. The records show that more than 10,000 Florentines were charged with sodomy in the seventy-five years ending in 1505; some 2,000 were convicted. Only a few were executed, but the rest were exiled, branded, fined or publicly humiliated.

Vasari says that before his death Leonardo lamented that he had “offended God and mankind by not working harder at his art.” Vasari also tells of an unlikely deathbed conversion, in which Leonardo “earnestly resolved to learn the doctrines of the Catholic faith . . . and then, lamenting bitterly, he confessed and repented, and though he could not stand up, supported by his friends and servants he received the blessed sacrament from his bed.”

Perhaps it happened. Perhaps, like the rest of us, Leonardo sometimes doubted his own beliefs; perhaps he was afraid that, after all, he might be wrong. We will never know for sure, and he leaves us with that mystery along with all the others. But that also offers a morsel of reassurance for the rest of us, craving some common bond with him: Leonardo da Vinci may have been the smartest man who ever lived, but, like us, he was human.

The earliest known portrait of Leonardo is believed to be this statue of David by Verrocchio.

1833 engraving of Leonardo

Leonardo helped his master, Verrocchio, to finish “The Baptism of Christ.” His contribution, the angel at far left, and the background, is the first painting that can be assigned to him.

The small white dog trotting along with Verrocchio’s “Tobias and the Angel” is unmistakably Leonardo’s work.

“The Annunciation” is Leonardo’s first completed painting. It was probably finished over a period of years.

Leonardo’s first known portrait is of a prominent young Florentine woman, Ginevra de’ Benci.

Leonardo sketched the body of assassin Bernardo Bandino hanging from a window of the Bargello.

Leonardo’s “Lady with an Ermine,” a portrait of the Duke of Milan’s mistress

Leonardo’s famed Vitruvian Man.

Leonardo’s horse in Milan

Mona Lisa

Leonardo’s painting of Bianca Sforza

Leonardo’s “The Last Supper” adorns the back wall of this church in Italy

“The Last Supper”

Leonardo’s painting of Mary and her mother, St. Anne, with the infant Christ

Harbor in Cesenatico, Italy, designed by Leonardo

Statue of Leonardo in Milan

Statue of Leonardo in Florence

Statue of Leonardo in Vienna

The house where Leonardo died

Leonardo’s tomb in France

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Published by New Word City LLC, 2014

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© Anna Abraham

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