Whereupon the Republic, which at first had raised a feeble, make-believe protest at the action of her condottiero, now deemed it as well to find a pretext for supporting him.

So Venice alleged that a courier of hers had been stripped of a letter, and, with such an overwhelming cause as that for hostilities, dispatched reinforcements to d'Alviano to the end that he might restore Pandolfaccio to a dominion in which he was abhorred.
Further, d'Alviano was thereafter to proceed to do the like office for Giovanni Sforza, who already had taken ship for Pesaro, and who was restored to his lordship on September 3.
Thence, carrying the war into the Romagna itself, d'Alviano marched upon Cesena.

But the Romagna was staunch and loyal to her duke.

The governor had shut himself up in Cesena with what troops he could muster, including a thousand veterans under the valiant Dionigio di Naldo, and there, standing firm and resolute, he awaited the onslaught of the Venetians.
D'Alviano advanced rapidly and cruelly, a devastator laying waste the country in his passage, until to check him came suddenly the Borgia troops, which had ventured upon a sally.

The Venetians were routed and put to flight.
On September 16 the restored tyrants of Rimini, Pesaro, Castello, Perugia, Camerino, Urbino, and Sinigaglia entered into and signed at Perugia a league, whose chiefs were Bartolomeo d'Alviano and Gianpaolo Baglioni, for their common protection.
Florence was invited to join the allies.