León Trotsky was a Russian revolutionary and Marxist theorist born on November 7, 1879. He played a key role in the Russian Revolution of 1917 and was a prominent leader in the early Soviet government. Trotsky is best known for his theory of permanent revolution and for organizing the Red Army during the Russian Civil War. In 1927, Trotsky was expelled from the Communist Party by Joseph Stalin and subsequently exiled from the Soviet Union. He continued to criticize Stalin's policies and advocated for international socialism. Trotsky was assassinated in Mexico City on August 21, 1940, by a Soviet agent.