The French had been victorious at Ravenna the previous year. Nevertheless, the French under King Louis XII were driven out of the city of Milan the following month by the Holy League.
In 1513, the French army of 10,000 under Louis de la Trémoille was besieging the city of Novara, which was held by some of the Duke of Milan's Swiss mercenaries. It has been argued that the Swiss may have intended to annex part (or all) of Milan to the Swiss Confederation. Novara, c. 40 kilometers west of Milan, was the second most important city of the Milanese duchy.
However, the French were surprised at their camp there on June 6 by a Swiss relief army of some 13,000 troops, who came to relieve their forces in the town. The German Landsknecht mercenaries of the French, pike-armed like the Swiss, were able to form up into heavy squares, and the French were able to deploy some of their artillery. Despite this, the Swiss onslaught, sweeping in from multiple directions due to forced marches which achieved encirclement of the French camp, took the French guns, pushed back the Landsknecht infantry regiments, and destroyed the Landsknecht squares. Caught off guard, the French heavy cavalry, their decisive arm, was unable to properly deploy, and played little role in the fight.
The battle was particularly bloody, with 5,000 casualties (other sources state up to 10,000) on the French side, and moderate losses for the Swiss pikemen, mostly suffered from the French artillery as the Swiss moved into the attack. 700 men were killed in three minutes by heavy artillery fire. Additionally, after the battle, the Swiss executed the hundreds of German mercenaries they had captured who had fought for the French. Having routed the French army, the Swiss were unable to launch a close pursuit because of their lack of cavalry, but several contingents of Swiss did follow the French withdrawal all the way to Dijon before the French paid them off to leave France. The Swiss captured 22 French guns with their carriages.
The French defeat forced Louis XII to withdraw from Milan and Italy in general, and led to the temporary restoration of Duke Maximilian Sforza, although he was widely regarded to be the puppet of his Swiss mercenaries and "allies", who held real military power in Milan.
^The Swiss were, for all practical purposes, entirely in control of the Duchy, while Sforza was regarded as their puppet. Nevertheless, the battle is sometimes presented as one between the French and the Milanese.
^Sforza was present at the battle, and, being the nominal employer of the Swiss, may be considered their leader. It is extremely doubtful, however, that he exercised any actual command.
^According to other sources, the total amounted to 1,200 cavalry and c. 20,000 Landsknechts, Gascony and other troops.
^Merriman, John. A History of Modern Europe, Volume One, p. 35.