The Truman Doctrine, announced in 1947, pledged support to countries threatened by communism. It marked the start of the U.S. policy of containment, aiming to stop the spread of communism and became a key component of American foreign policy during the Cold War.

The Truman Doctrine set the stage for various U.S. interventions around the world, as America sought to support free countries against authoritarian regimes. It is seen as a defining moment in the ideological battle between the U.S. and the Soviet Union.