In 1482, Leonardo moved to Milan. He was now a master, but he seemed dissatisfied with his life in Florence. Science interested him just as much as painting, and he had begun making copious scientific speculations in his notebooks. Thus even though Milan was less artistically-centered than Florence, the city would provide him with more opportunities to apply his various interests.
But his primary motivation for moving was probably the opportunity to work for Milan's ruler, Ludovico Sforza: Milan held a highly strategic position in southwestern Europe, and was often a point of military contention; in a letter Leonardo wrote to Sforza before coming to the city, he offers his services as a military engineer. Although it is unclear whether Leonardo ever actually sent this letter, it proves Leonardo's strong interest in military engineering. During this time, Leonardo designed a number of military machines, including a primitive form of war tank and a wild chariot with scythes attached to its wheels. The aforementioned letter also alludes to an equestrian monument Sforza hoped to erect in honor of his father; Leonardo planned a gigantic horse to serve this purpose–one that would be a feat of engineering as well as art.
When Leonardo first arrived, however, his first major project was another painting, the Virgin of the Rocks.
Leonardo painted the work for the Confraternity of the Immaculate Conception in Milan; two brothers named de Predis painted the side panels. The contract with the Confraternity led to many legal problems, so much so that Leonardo eventually had to supervise the painting of a second version of the painting, in 1506.
Perhaps the most striking aspect about the Virgin of the Rocks is the Virgin's placement on rocks. A precipitous chasm separates the viewer from the holy scene, as if it were taking place on some unattainable plane of being. The rocky caves in the background, opening up onto a hazy landscape, contribute to the sense of otherworldliness. Leonardo often used hazy, rocky background, and this provides the extreme example. The Virgin herself is the most mature woman we have seen him paint at this point in his career. Her head is longer and more natural than the round, stylized faces of earlier paintings. An angel sits to her left, an infant John the Baptist toddles at her right, and the Christ Child rests at her feet. They form a triangle reminiscent of the Adoration of the Magi. The angel points at John the Baptist, and just above her hand hovers Mary's hand, open yet domineering. In the same vertical line, Christ lifts two pudgy fingers in benediction.
Even while he entrenched himself in this complex painting, Leonardo was beginning serious research into anatomy. In order to gain knowledge about the workings of the human body he learned to dissect cadavers; the resultant sketches and diagrams are some of the most meticulous studies of the human body made before the twentieth century. Not only did he fully record the known structure and functions of the body; he also made numerous revolutionary discoveries about anatomy, all of which contradicted contemporary medical beliefs. His interest in anatomy would persist throughout his life. As with many of his studies, he planned eventually to collect the results into a book– in this case the title was to be Of the Human Figure. However, like so many of his paintings, none of these books ever came to completion.
Leonardo seems to have become a prominent figure in Sforza's court fairly soon after his arrival in Milan. During the 1480s, he worked on two famous portraits, the Portrait of a Musician and the Lady with an Ermine. He also began work on the bronze horse. Sforza, who was not the legitimate ruler of Milan, was eager to erect monuments that would remind the town of his heritage and authority: the large equestrian statue was to honor his father. Leonardo planned a horse that would stand twenty feet tall and comprise 200,000 pounds of bronze. Never had a bronze statue approached this size, and Leonardo never had the chance to cast it, though he continued to work on different designs, molds, and models throughout the 1880s and 1890s. The project took up a great deal of his time, and was one of his greatest failures. When the French invaded Milan in 1499, idle archers used the model of the horse for crossbow practice.
The pattern of work that we see Leonardo developing in Milan would come to persist throughout his life: while conducting intense scientific investigations in his spare time, the artist would work on one or two major public projects (such as a monument or mural), doing a few portraits on the side.