Truman Doctrine.
The Truman Doctrine was an American foreign policy whose stated purpose was to counter Soviet geopolitical expansion during the Cold War. It was first announced to Congress by President Harry S. Truman on March 12, 1947, and further developed on July 12, 1948, when he pledged to contain threats to Greece and Turkey.
The Truman Doctrine became the foundation of American foreign policy, and led, in 1949, to the formation of NATO, a military alliance that is still in effect. Historians often use Truman's speech to date the start of the Cold War.
