After the death of Lenin (January 1924) and the rise of Joseph Stalin, Trotsky lost his government positions; he was eventually expelled from the Soviet Union in February 1929. He spent the rest of his life in exile, writing prolifically and engaging in open critique of Stalinism. In 1938 Trotsky and his supporters founded the Fourth International in opposition to Stalin's Comintern. After surviving multiple attempts on his life, Trotsky was assassinated in August 1940 in Mexico City by Ramón Mercader, a Soviet NKVD agent. Written out of Soviet history books under Stalin, Trotsky was one of the few Soviet political personalities whom the Soviet administration under Nikita Khrushchev did not rehabilitate in the 1950s.