(Sept. 25–Oct. 20, 1805) Major victory by France over Austria at Ulm, Bavaria.
In August 1805 Austria joined the Anglo-Russian alliance against Napoleon and on September 11 sent 72,000 troops under Baron Karl Mack (1752–1828) into Bavaria, an ally of France. Napoleon, hoping to crush the Austrians before Russian troops could join them, sent his Grand Army of 210,000 French troops across the Rhine River, marching 18 mi (29 km) a day to reach the Danube River on September 25. After several battles, he encircled the Austrians and forced them into the city of Ulm, where they faced French artillery attacks. Seeing little chance that his troops could hold out until Russian reinforcements arrived, Baron Mack surrendered on October 20 with about 50,000 men.