The Truman Doctrine comes from a speech delivered by president Harry Truman in Congress on March 12, 1947. The British government had announced that it would withdraw its economic assistance to the Greek and Turkish governments; Greece was battling a communist guerrilla.
Truman told congressmen that the USA would assume the responsibility of providing economic aid and military support to Greece. The Truman Doctrine says that the US will provide economic, military and diplomatic support to any nation under the threat of internal or outside forces (that meant communist insurgency or a direct Soviet threat in practice). In this way, he said goodbye to traditional isolationism and heralded a regular involvement in foreign affairs.
