Soon after the end of the Second World War, the two former allies, the Soviet Union and the United States, became locked in a Cold War (1947–1991), a continuing state of political conflict and military tension. This aligned the Soviet Union's satellite states (often referred to as the Eastern Bloc) against the powers of the Western world, allied with the United States. The primary participants' military forces never clashed directly, but expressed this conflict through military coalitions, strategic conventional force deployments, extensive aid to states deemed vulnerable, proxy wars, espionage, propaganda, a nuclear arms race, and economic and technological competitions, such as the Space Race.