In 1917, the Russians had a revolution, which led to them leaving the war in March 1918. Also in 1917, the United States entered the war, though it took a year for their main army to arrive. In the gap between when the Russians left and the Americans arrived, the Germans launched a huge attack in March 1918 to try to win the war, but it was not enough. In August-November 1918, the Allied Powers won a big victory against the Germans in the Hundred Days Offensive. Austria-Hungary and the Ottoman Empire then agreed to stop fighting. The German government collapsed and a new government agreed to end the war on 11 November.