On 17 July, Venetian forces commanded by Andrea Gritti marched quickly from Treviso with a contingent of stradioti and retook the city, which had been garrisoned by some landsknechts hired by Emperor Maximilian I.

In early August 1509, Maximilian set out from Trento with some 35,000 men and headed south into Venetian territory; there he was joined by French and Papal contingents.

For two weeks, Imperial and French artillery bombarded the city, successfully breaching the walls; but the attacking troops were driven back by determined Venetian resistance when they attempted to enter.

An assault by 7,500 Landsknechts in the Codalunga sector of the walls (the one that was most bombarded during the siege) was repulsed by mercenary commander Citolo da Perugia, whose mines killed 300 attackers and injured 400 others.

By 30 September, Maximilian, unable to pay his mercenaries, lifted the siege; leaving a small detachment in Italy under the Duke of Anhalt, he withdrew to Tyrol with the main part of his army.