The Battle of Bicocca, sometimes known as the Battle of La Bicocca, was fought on April 27, 1522, during the Italian War of 1521–26. A combined French and Venetian force under Odet de Foix, Vicomte de Lautrec, was decisively defeated by an Imperial, Spanish, and Papal army under the overall command of Prosper Colonna. Lautrec then withdrew from Lombardy, leaving the Duchy of Milan in Imperial hands.
Having been driven from Milan by an Imperial advance in late 1521, Lautrec had regrouped, attempting to strike at Colonna's lines of communication. When the Swiss mercenaries in French service did not receive their pay, however, they demanded an immediate battle, and Lautrec was forced to attack Colonna's fortified position in the park of Bicocca, north of Milan. The Swiss pikemen advanced over open fields under heavy artillery fire to assault the Imperial positions, but were halted at a sunken road backed by earthworks. Having suffered massive casualties from the fire of Spanish arquebusiers, the Swiss retreated. Meanwhile, an attempt by French cavalry to flank Colonna's position proved equally ineffective. The Swiss, unwilling to fight further, marched off to their cantons a few days later, and Lautrec retreated into Venetian territory with the remnants of his army.
The battle is noted chiefly for marking the end of the Swiss dominance among the infantry of the Italian Wars, and of the Swiss method of assaults by massed columns of pikemen without support from other troops. It was simultaneously the first of a series of engagements which established the decisive role of firearms on the battlefield.