The Cold War (often dated 1947–1991) was a sustained state of political and military tension between the powers of the Western world, led by the United States and its NATO allies, and the communist world, led by the Soviet Union, its satellite states and allies. This began after the success of their temporary wartime alliance against Nazi Germany, leaving the USSR and the US as two superpowers with profound economic and political differences. The Soviet Union created the Eastern Bloc with the eastern European countries it occupied, maintaining these as satellite states. The post-war recovery of Western Europe was facilitated by the United States' Marshall Plan, while the Soviet Union, wary of the conditions attached, declined and set up COMECON with its Eastern allies. The United States forged NATO, a military alliance using containment of communism as a main strategy through the Truman Doctrine, in 1949, while the Soviet bloc formed the Warsaw Pact in 1955. Some countries aligned with either of the two powers, whilst others chose to remain neutral with the Non-Aligned Movement.