On 15 April 1509, a French army under the command of Louis XII left Milan and invaded Venetian territory. To oppose its advance, Venice had massed a mercenary army near Bergamo, jointly commanded by the Orsini cousins, Bartolomeo d'Alviano and Niccolò di Pitigliano.

On 14 May, as the Venetian army moved south, Alviano's rearguard, commanded by Piero del Monte and Saccoccio da Spoleto, was attacked by a French detachment under Gian Giacomo Trivulzio, who had massed his troops around the village of Agnadello. Despite being initially successful, the Venetian cavalry was soon outnumbered and surrounded; when Alviano himself was wounded and captured the formation collapsed and the surviving knights fled from the battlefield. Of Alviano's command, more than four thousand were killed, including his commanders Spoleto and del Monte, and 30 pieces of artillery were captured.

Although Pitigliano had avoided engaging the French directly, news of the battle reached him by that evening, and the majority of his forces had deserted by morning. Faced with the continued advance of the French army, he hurriedly retreated towards Treviso and Venice. Louis then proceeded to occupy the remainder of Lombardy. The battle is mentioned in Machiavelli's The Prince, noting that in one day, the Venetians "lost what it had taken them eight hundred years' exertion to conquer."