Soviet Union (Union of Soviet Socialist Republics, USSR)

Created on 30 December 1922, following the Bolshevik victory in the Russian Civil War. Nominally a federation of Russia, Ukraine, Belarus and Transcaucasia, its power was centralized in Moscow. More republics were created with other administrative entities for smaller ethnic minorities. Despite the Nazi-Soviet pact, Germany attacked in 1941 and only retreated after the battle of Stalingrad (1942-43). Soviet casualties were estimated at 20 million. After the war, the USSR dominated the Warsaw Pact. This period corresponded with the Cold War conflict with western Europe and the USA, which gradually gave way to détente. The USSR became disastrously involved in a guerrilla war in Afghanistan in 1979, and in the 1980s it faced serious economic problems. Formally dissolved on 30 December 1991 after revolts by the nationalities, its successor was the Commonwealth of Independent States.