In 1447, attacked by Alfonso V of Aragon, King of Naples, he defended it with the help of a Florentine army. He was therefore named captain of the Republic of Florence and, in 1450, moved against Alfonso's troops which were besieging Castiglione della Pescaia, but without effect.
In 1447, the ruler resisted an attack by Alfonso V of Aragon, King of Naples, and successfully defended the city with the help of a Florentine army. This led to his appointment as captain of the Republic of Florence in 1450, but he was unable to repel Alfonso's siege of Castiglione della Pescaia.