The Truman Doctrine was a U.S. foreign policy announced by President Harry S. Truman on March 12, 1947, which pledged American economic and military support to countries threatened by communism or authoritarian subjugation, specifically Greece and Turkey at the time. Truman asked Congress for $400 million to aid these nations, which were seen as vulnerable to Soviet influence and communist insurgencies. The doctrine marked a shift from wartime alliance with the Soviet Union to a policy of containing Soviet expansion during the Cold War. Truman declared that it was U.S. policy to support "free peoples who are resisting attempted subjugation by armed minorities or by outside pressures," framing the struggle against communism as essential to international peace and U.S. national security. The policy was rooted in the fear that if Greece and Turkey fell to communism, other countries in the region and beyond would follow-a concept later known as the "domino theory." This doctrine laid the foundation for U.S. Cold War policy worldwide, including the formation of NATO and subsequent interventions in Korea, Cuba, and Vietnam. The Truman Doctrine also symbolized a broader commitment to support anti-communist regimes globally, regardless of their democratic credentials, and to use American economic power to stabilize regions without direct military intervention initially. It represented a decisive end to U.S. isolationism, signaling a new era of active American engagement in global affairs to contain communism
