The earliest known dated work of Leonardo's is a drawing done in pen and ink of the Arnovalley, drawn on the 5th of August 1473. It is assumed that he had his own workshop between 1476 and 1478, receiving two orders during this time. From around 1482 to 1499, Ludovico Sforza, Duke of Milan, employed Leonardo and permitted him to operate his own workshop complete with apprentices. It was here that seventy tons of bronze that had been set aside for Leonardo's "Gran Cavallo" horse statue (see below) were cast into weapons for the Duke in an attempt to save Milan from the French under Charles VIII in 1495.
When the French returned under Louis XII in 1498, Milan fell without a fight, overthrowing Sforza. Leonardo stayed in Milan for a time, until one morning when he found French archers using his life-size clay model of the "Gran Cavallo" for target practice. He left with Salai and his friend Luca Pacioli (the first man to describe double-entry bookkeeping) for Mantua, moving on after 2 months to Venice (where he was hired as a military engineer), then briefly returning to Florence at the end of April 1500.
Entered the services of Cesare Borgia
In Florence he entered the services of Cesare Borgia, the son of Pope Alexander VI, acting as a military architect and engineer; with Cesare he travelled throughout Italy. In 1506 he returned to Milan, now in the hands of Maximilian Sforza after Swiss mercenaries had driven out the French.From 1513 to 1516, he lived in Rome, where painters like Raphael and Michelangelo were active at the time, though he did not have much contact with these artists. However, he was probably of pivotal importance in the relocation of David (in Florence), one of Michelangelo's masterpieces, against the artist's will.
In 1515 Francis I of France retook Milan, and Leonardo was commissioned to make a centrepiece (a mechanical lion) for the peace talks between the French king and Pope Leo X in Bologna, where he must have first met the King. In 1516, he entered Francis' service, being given the use of the manor house Clos Lucé (also called "Cloux") next to the king's residence at the royal Chateau Amboise. The King granted Leonardo and his entourage generous pensions: the surviving document lists 1000 écus for the artist, 400 for Melzi (named "apprentice") and 100 for Salai (named "servant"). In 1518 Salai left Leonardo and returned to Milan, where he eventually perished in a duel. Francis became a close friend.
Leonardo da Vinci died at Clos Lucé, France, on 2nd May, 1519. According to his wish, 60 beggars followed his casket. He was buried in the Chapel of Saint-Hubert in the castle of Amboise. Melzi was his principal heir and executor, but Salai was not forgotten: he received half of Leonardo's vineyard.