 The Russian Soviet Federative Socialist Republic (called "Russian Socialist Federative Soviet Republic" at the time), together with the Ukrainian, Byelorussian, and Transcaucasian Soviet Socialist Republics, formed the Union of Soviet Socialist Republics (USSR), or Soviet Union, on 30 December 1922.Out of the 15 republics that would make up the USSR, the largest in size and over half of the total USSR population was the Russian SFSR, which came to dominate the union for its entire 69-year history.Following Lenin's death in 1924, a troika was designated to govern the Soviet Union.