These circumstances becoming known to the opposite league, induced it also to provide for war.  The duke of Milan appointed as his general, Federigo d’Urbino; the Florentines engaged Costanzo, lord of Pesaro; and to sound the disposition of the pope, and know whether the Venetians made war against Ferrara with his consent or not, King Ferrando sent Alfonso, duke of Calabria, with his army across the Tronto, and asked the pontiff’s permission to pass into Lombardy to assist the marquis, which was refused in the most peremptory manner.  The Florentines and the king, no longer doubtful about the pope’s intentions, determined to harass him, and thus either compel him to take part with them, or throw such obstacles in his way, as would prevent him from helping the Venetians, who had already taken the field, attacked the marquis, overran his territory, and encamped before Figaruolo, a fortress of the greatest importance.  In pursuance of the design of the Florentines and the king, the duke of Calabria, by the assistance of the Colonna family (the Orsini had joined the pope), plundered the country about Rome and committed great devastation; while the Florentines, with Niccolo Vitelli, besieged and took Citta di Castello, expelling Lorenzo Vitelli, who held it for the pope, and placing Niccolo in it as prince.

The pope now found himself in very great straits; for the city of Rome was disturbed by factions and the country covered with enemies.  But acting with courage and resolution, he appointed Roberto da Rimino to take the command of his forces; and having sent for him to Rome, where his troops were assembled, told him how great would be the honor, if he could deliver the church from the king’s forces, and the troubles in which it was involved; how greatly indebted, not only himself, but all his successors would be, and, that not mankind merely, but God himself would be under obligations to him.  The magnificent Roberto, having considered the forces and preparations already made, advised the pope to raise as numerous a body of infantry as possible, which was done without delay.  The duke of Calabria was at hand, and constantly harassed the country up to the very gates of Rome, which so roused the indignation of the citizens, that many offered their assistance to Roberto, and all were thankfully received.  The duke, hearing of these preparations, withdrew a short distance from the city, that in the belief of finding him gone, the magnificent Roberto would not pursue him, and also in expectation of his brother Federigo, whom their father had sent to him with additional forces.  But Roberto, finding himself nearly equal to the duke in cavalry, and superior in infantry, marched boldly out of Rome and took a position within two miles of the enemy.  The duke, seeing his adversaries close upon him, found he must either fight or disgracefully retire.  To avoid a retreat unbecoming a king’s son, he resolved to face the enemy; and a battle ensued