The Union of Soviet Socialist Republics (USSR) was a federal socialist state that existed from 1922 to 1991. It was made up of multiple republics, with the largest being Russia. The USSR was established after the Russian Revolution and aimed to create a classless society based on Marxist principles. The USSR played a significant role in global events, particularly during the Cold War, when it was a major rival to the United States. It was known for its centralized economy, state control of resources, and significant achievements in science and technology, including the launch of Sputnik, the first artificial satellite.