Foreign policy inititated by
Harry S. Truman, a few years after
World War II. The main point of the policy is
containment of the spread of
communism across the
globe.
After the Berlin Airlift incident, Truman decided that the USSR politburo was intent of world domination. In combination of the Marshall Plan, which offered aid to rebuilding Europe (and indirectly strengthened existing governments to prevent communist uprisings), America attempted to stop the communist "threat".
Overall, this policy was quite successful and prevented the election of communist regimes in countries such as Greece, France and Italy.