The Soviet Union has a single party system dominated by the Communist party. Although the USSR is nominally a union of Soviet Republics (of which there were 15 after 1956) with the capital in Moscow, it is in actuality a highly centralized state with a planned economy. Much of Soviet society is overseen by national security agencies such as the KGB (which has been active since 1954).
The Soviet Union was founded in December 1922. It is largely due to the Russian Revolution of 1917 and emerged victorious in the ensuing Russian Civil War, unified with the Transcaucasian, Ukrainian and Belarussan SSR's. After the death of Vladimir Lenin, the first Soviet leader, power was eventually consolidated by Joseph Stalin who led the country through a large-scale industrialization with command energy and political repression. During World War II, in June 1941, the Soviet Union was attacked by Germany, a country with whom it had signed a non-aggression pact. After four years of warfare, the Soviet Union emerged as one of the world's two superpowers, extending its influence into much of Eastern Europe and beyond.
The Soviet Union and its satellites from the Eastern Bloc were one of two participating factions in the Cold War and World War III.