The policy of containment was a diplomatic strategy of the United States to prevent the spread of the communism during the Cold War. Economic support should bind countries to the United States. This was a counteraction against the new Soviet sphere of influence.
In March 1947 the US president Harry Truman (1884-1972) announced support for countries which were threatened by military force. This speech is called "Truman Doctrine" nowadays. In detail he promised support for Greece and Turkey against the Soviet Union.
The most important part of the policy of containment was the "European Recovery Program" (1948), also known as "Marshall Plan", which should boost the European economy after the destruction in the Second World War using—most important—money, successful American economic models and less European trade barriers.