The Cold War was a state of political and military tension between communist states led by the Soviet Union and capitalist states led by the United States from 1946 to 1991. It arose due to differences on the postwar occupation of Germany and Eastern Europe, with Stalin wanting Soviet control and the US/UK wanting independence. In response to Soviet domination of Eastern Europe, President Truman promised aid through the Truman Doctrine and pursued a policy of containment to prevent the spread of communism. The Iron Curtain symbolized the ideological and physical division of Europe between communist East and capitalist West. Stalin's blockade of Berlin led the US and UK to supply West Berlin through an massive airlift in response.