What policy did President Harry Truman institute to assist countries threatened by communism?

The Truman Doctrine was a significant policy introduced by President Harry Truman in 1947 aimed at providing military and economic assistance to countries resisting the spread of communism. The doctrine emerged in the context of the Cold War, particularly as Greece and Turkey faced pressure from communist movements and external forces. By declaring that the United States would support free peoples who were resisting subjugation, Truman set a precedent for American international involvement based on the principle of containment, which sought to prevent the expansion of communism beyond its existing borders.

This policy reinforced the idea that the U.S. would confront communist aggression and pledged American support to nations threatened by communist influence. The Truman Doctrine not only marked a shift in U.S. foreign policy towards an active stance against communism but also laid the groundwork for subsequent actions and programs, such as the Marshall Plan, which focused on rebuilding Europe economically to foster stability and reduce the appeal of communism.