Vladimir Lenin (Владимир Ильич Ленин) (22 April 1870 - 21 January 1924) was the first leader of the Soviet Union. He was absolutely essential to the country in its infancy.
Lenin, a communist, opposed Russia's involvement in World War I and believed in the proletarian revolution called for by Karl Marx. During the war, he participated in the Russian Revolution as leader of the Bolshevik faction. He was thus involved in the regicide against Tsar Nicholas II. He led the Bolsheviks during an ensuing power struggle in which he was opposed by most western governments. Under his leadership, the Bolsheviks came to dominate Russian politics, and Lenin was proclaimed premier of the new Union of Soviet Socialist Republics in 1922.
He was also a political theorist whose works would rival Marx's in their influence over future generations of communists. His political theories have collectively come to be called Leninism.
Lenin died at age 53 on 21 January 1924. Officially, his cause of death was a series of strokes which he'd suffered over the last two years of his life. He was succeeded by Joseph Stalin, whom Lenin had expressed opposition to prior to his death. Stalin created a posthumous cult of personality around Lenin that continued until the dissolution of the Soviet Union in 1991.