Leon Trotsky was a Russian revolutionary, Marxist theorist, and Soviet politician. He was one of the leaders of the October Revolution of 1917, which overthrew the Tsarist government and established the Soviet Union. Trotsky was a key figure in the early years of the Soviet Union, and was a major influence on the development of Marxist theory. He was also a leading figure in the Left Opposition, a group of Marxist revolutionaries who opposed the policies of Joseph Stalin. Trotsky was eventually exiled from the Soviet Union and assassinated in Mexico in 1940. He is remembered as a revolutionary leader and a major contributor to Marxist thought.