Can you describe the United States policy of containment and show an example of an event when the policy was used and why?

The "containment policy" was the U.S. approach to containing, or preventing, the spread of Communism after World War II. The idea was to make other countries prosperous enough to avoid the temptation of communism.

An early test of containment came in Greece and Turkey. In 1946, a civil war broke out in Greece, pitting Communist groups against the British-supported government. At the same time, the Soviet Union was pressuring Turkey to allow it to build naval bases on its northwestern coast, thereby giving the Soviet Black Sea Fleet easy access to the Mediterranean. When Great Britain announced it no longer had the resources to help Greece and Turkey meet the threats to their independence, the United States stepped in. President Truman asked Congress for $400 million in military and economic aid for Greece and Turkey in March 1947. Truman cited the United States' obligation to back free peoples who were resisting control by an armed minority or outside pressures. This policy, known as the Truman Doctrine, appeared to work: The Communists were defeated in the Greek Civil War in October 1949; and the foreign aid helped strengthen the Turkish economy.

Truman's "doctrine" was part of an overall containment strategy. Other elements of the strategy included the Marshal Plan, the Four Point program, and NATO.