The Truman Doctrine was a US policy to stop Soviet expansion during the Cold War. United States President Harry S. Truman pledged to contain communism in Europe and elsewhere and impelled the US to support any nation with both military and economic aid if its stability was threatened by communism or the Soviet Union. The Truman Doctrine became the foundation of the president's foreign policy and placed the U.S. in the role of global policeman. As Foner reminds us, the Truman Doctrine "set a precedent for American assistance to anticommunist regimes throughout the world, no matter how undemocratic, and for the creation of a set of global military alliances directed against the Soviet Union" (1st edition, p. 781; 2nd edition, p. 844). President Harry S. Truman told Congress that "it must be the policy of the United States to support free people who are resisting attempted subjugation by armed minorities or by outside pressures." Truman reasoned, because these "totalitarian regimes" coerced "free peoples", they represented a threat to international peace and the national security of the United States. Truman made the plea amid the crisis of the Greek Civil War (1946–1949). He argued that if Greece and Turkey did not receive the aid that they urgently needed, they would inevitably fall to communism with grave consequences throughout the region. Because Turkey and Greece were historic rivals, it was necessary to help both equally, even though the threat to Greece was more immediate.
For years Britain had supported Greece, but was now near bankruptcy and was forced to radically reduce its involvement. In February 1947, Britain formally requested the United States take over its role in supporting the Greek government.
The policy won the support of Republicans who controlled Congress and involved sending $400 million in American money, but no military forces, to the region. The effect was to end the Communist threat, and in 1952 both countries (Greece
and Turkey) joined NATO, a military alliance that guaranteed their protection.
The Doctrine was informally extended to become the basis of American Cold War policy throughout Europe and around the world. It shifted American foreign policy toward the Soviet Union from détente (a relaxation of tension) to a policy of containment of Soviet expansion as advocated by diplomat George Kennan.