Final answer:
The Truman Doctrine committed the United States to assist countries that were threatened by Communist takeover, starting with substantial aid to Greece and Turkey to suppress Communist rebels and resist Soviet pressures.
Step-by-step explanation:
Under the Truman Doctrine, the United States agreed to assist countries whose governments were in danger of being overthrown by communist forces. Announced by President Truman in 1947, this policy was instrumental in providing financial and military aid to Greece and Turkey. Truman's commitment to support 'free peoples' against the pressures of communism was part of a broader strategy to contain the spread of Communist influence during the post-World War II era, especially in the strategic Mediterranean region. This doctrine laid the groundwork for America's foreign policy throughout the Cold War, promising intervention to preserve democracy and thwart Soviet expansion.