What year did da Vinci collaborate with Marcantonio della Torre ?
He was the son of Francesco della Torre ( brother of Napoleone della Torre ) and Giulia Castiglioni , As part of the factional turmoil between the Guelphs and Ghibellines , the conflict of Guido ’s Guelph family with the Ghibelline Visconti , led by Ottone Visconti , dominated much of his childhood .