The subject was also military: an incident in the long and bitter struggle between Florence and Pisa, when Sir John Hawkwood (then in the pay of the Pisans, before he came over finally to the Florentines) attacked a body of Florentines who were bathing in the river.

The scene gave the young artist scope both for his power of delineating a spirited incident and for his drawing of the nude, and those who saw it said of this work that it was finer than anything the painter ever did.

While it was in progress all the young artists came to Sant' Onofrio to study it, as they and its creator had before flocked to the Carmine, where Masaccio's frescoes had for three-quarters of a century been object-lessons to students.
What became of the cartoon is not definitely known, but Vasari's story is that Bandinelli, the sculptor of the Hercules and Cacus outside the Palazzo, who was one of the most diligent copyists of the cartoon after it was placed in a room in this building, had the key of the door counterfeited, and, obtaining entrance during a moment of tumult, destroyed the picture.

The reasons given are: (1, and a very poor one) that he desired to own the pieces; (2) that he wished to deprive other and rival students of the advantage of copying it; (3) that he wanted Leonardo to be the only painter of the Palazzo to be considered; and (4, and sufficient) that he hated Michelangelo.

At this time Bandinelli could not have been more than eighteen.