Traditionally the USA wanted to have little to do with the international fears (isolationism), but after Soviet takeover of Eastern Europe the USA became active throughout the world.
In the years following the war there were poor harvests and cold winters. People in Britain were rationing, Germany was dying from hunger, and France and Italy support for communism was rising.
In February 1947 the British government told America that they could no longer pay for troops in pro-western Greece and Turkey, and that unless the USA replaced them there was a real possibility that they (and in time the rest of Europe) would fall into the Soviet Sphere. In response on March 12th 1947 Truman called upon the US to “support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures”.
Aid was given by the United States to Greece and Turkey for both political and military reasons. The political reason was guided by the new policy of containment, the idea to stop what it called the domino effect of nations moving politically towards communism, rather than capitalism by using its wealth and power. The United States was also cautious of a third World War, and needed military advantages over the Soviet Union if they were to win. Therefore Truman signed the act into law on May 22, 1947 granting $400 million ($300 million to Greece and $100 million to Turkey) in military and economic aid.
With success in Greece and Turkey Truman went even further and declared that the USA would support anyone who wished to fight communism. Italy and France were given a variety of assistance and encouraged to keep their powerful communist groups out of government. Initially the Truman Doctrine was applied in the Middle East and Europe, but it eventually spread to the whole world.
The Truman Doctrine and the Marshall Plan changed the world and benefited not only the United...