C. The Truman Doctrine most directly illustrated the United States' departure from isolationist policies following World War II. The Truman Doctrine was a policy that pledged to provide economic and military assistance to countries threatened by communism. This marked a shift from the United States' traditional policy of not getting involved in the affairs of other nations, which was a hallmark of isolationism.
The correct answer is C. the Truman Doctrine. The Truman Doctrine was a policy issued by President Harry Truman in 1947, which stated that the United States would provide economic and military assistance to support countries threatened by communism. This marked a departure from isolationist policies, as the United States became actively involved in international affairs and committed to preventing the spread of communism. The Berlin Airlift (A) and the Berlin Blockade (B) were events that occurred during the Cold War, but they specifically relate to the division of Germany and the Soviet blockade of West Berlin, rather than the United States' departure from isolationism. The Yalta Conference (D) was a meeting between the leaders of the United States, the Soviet Union, and the United Kingdom during World War II to discuss the reorganization of post-war Europe, but it does not directly illustrate the United States' departure from isolationist policies.
