Recto: a drawing of a group of horsemen advancing from the right with lances erect and banners streaming, forming a semicircle; on the extreme left is a slight sketch of a galloping horse; on the right are lightly sketched horsemen with trumpets. Verso: an indecipherable faint sketch, possibly of parts of horses. Melzi's number 113.

Leonardo’s most ambitious painting – albeit unfinished – was the Battle of Anghiari, a mural intended to be perhaps 60 feet (18 m) wide, depicting a celebrated Florentine victory of 1440 over the forces of Visconti Milan. The painting was commissioned in 1503 by the Florentine government for the Great Council Chamber of the Palazzo della Signoria. The painting was underway by June 1505 and proceeded until the summer of 1506, when Leonardo’s temporary return to Milan was requested by the French occupiers of that city, and permitted by the Florentine government for diplomatic reasons. Although Leonardo was back in Florence at least twice in 1507 and 1508, he never resumed the painting. Only the central portion, known as the Fight for the Standard, was substantially completed and this was obliterated – or, as has been claimed, concealed – after 1563.

The group occupying the right side of the composition of the Anghiari is seen in this drawing, and it is striking that Leonardo should prepare such a huge mural with such small, meticulously worked studies. The Florentine cavalry is gathered on a low hill, preparing to join the fray, their standards fluttering above, while in the left distance a horse gallops away towards the bridge that was key to the battle.

Text adapted from Leonardo da Vinci: A life in drawing, London, 2018