Final answer:
The Truman Doctrine established a precedent for proactive U.S. intervention to prevent the spread of Communism, signifying a major shift in American foreign policy during the Cold War.
Step-by-step explanation:
The Truman Doctrine established a precedent for United States intervention in foreign affairs during the Cold War. The doctrine emerged in 1947 when President Truman addressed Congress, requesting aid for Turkey and Greece to combat the spread of Communism. This foreign policy statement aligned with George Kennan's policy of containment, asserting that the U.S. would support free peoples resisting subjugation by armed minorities or external pressures. Congress approved $400 million in aid to these nations, which allowed them to withstand Communist forces, thereby setting a pattern for U.S. support and intervention in regions threatened by Communist expansion. The Truman Doctrine thus became the cornerstone of U.S. foreign policy, influencing Cold War dynamics and extending its reach beyond Europe into Asia, Africa, Latin America, and the Middle East.