What did the Truman Doctrine influence U.S. foreign policy during the Cold War?

The Truman Doctrine significantly shaped U.S. foreign policy during the Cold War by establishing a commitment to contain communism globally. Announced in 1947, it marked a shift from isolationism to active intervention, leading the U.S. to support countries resisting Soviet influence through military and economic aid. This doctrine set the precedent for subsequent policies, such as the Marshall Plan and military involvement in conflicts like Korea and Vietnam, framing the Cold War as a struggle between democracy and communism. Ultimately, it helped define the U.S. role as a global superpower committed to opposing Soviet expansion.