What was the main purpose of the Truman Doctrine?

The main purpose of the Truman Doctrine was to contain communism by aiding the countries of Greece and Turkey. In others words, the Truman Doctrine was a strong American foreign policy whose stated purpose was to counter Soviet geopolitical expansion during the Cold War. It was announced to the U.S. Congress by President Harry S. Truman on March 29, 1947. It was further developed on July 4, 1948 when President Truman pledged to contain explicit threats in Greece and Turkey.

With the Truman Doctrine, President Truman established that the United States of America would provide political, military, and economic assistance to all democratic nations under threat from external or internal authoritarian forces. The Truman Doctrine effectively reoriented U.S. foreign policy, away from its usual stance of withdrawal from regional conflicts not directly involving the United States, to one of possible intervention in far away conflicts.