Which events influenced the formulation of the Truman's doctrine?

The Truman Doctrine was influenced by several key events, notably the Greek Civil War and the Soviet Union's increasing influence in Eastern Europe. The U.S. feared the spread of communism, particularly after Britain announced it could no longer support Greece and Turkey. This led President Harry Truman to propose a policy of containment, pledging support to countries resisting communism. The doctrine was formally articulated in 1947, marking a significant shift in U.S. foreign policy towards active intervention to counter Soviet expansion.