In 1917, World War I caused the bad conditions for workers in factories to become even worse with a food shortage. People blamed it on the Tsar and rebelled. There were riots in cities such as St Petersburg and Moscow. The Tsar was soon forced to abdicate in the February Revolution in 1917. After the October Revolution he was assassinated with his family. In 1922 most of the Russian Empire became the Union of Soviet Socialist Republics, or USSR when a communist government won the Russian Civil War. Some of the counties in the Empire escaped but the biggest ones were forced into the USSR.