Leon Trotsky was a key figure in the Russian Revolution of 1917 and a prominent Marxist theorist. Born in 1879, he played a crucial role in the Bolshevik Party alongside Vladimir Lenin. Trotsky was known for his ideas on permanent revolution, which argued that socialist revolutions should spread globally rather than remain confined to one country. After Lenin's death, Trotsky became a rival to Joseph Stalin for leadership of the Soviet Union. His opposition to Stalin's policies led to his exile in 1929. Trotsky continued to write and advocate for his beliefs until his assassination in 1940, leaving a lasting impact on socialist thought.