Sixtus had been rendered more eager to sue for peace by the series of victories by Venetian forces, who seized the opportunity to forward their territorial ambitions and had been hasty to declare war on Ferrara on a minor pretext.

Florence, Naples, Mantua, Milan, and Bologna have stood by Ferrara.

While the papal forces were holding in check the Neapolitans who sought to move north to aid Ferrara, and with the Roman Campagna being harassed by the Colonna, and Milan engaged in combat with Genoa, the Venetians had besieged Ferrara into starvation.

With the Venetians ready to take over Ferrara, the Pope, fearing his erstwhile allies, had suddenly changed sides: he made a treaty with Naples, and permitted the Neapolitan army to pass through his territories, giving them the chance to convey supplies to Ferrara and neutralize the siege.

At the same time the Pope had excommunicated the Venetians, and now urges all Italy to make war upon them.