Answer:
The Truman Doctrine and the Marshall Plan mark a dramatic shift in foreign policy because they turned American foreign policy into an imperialist and interventionist force, in full blown confrontation against the Soviet Union, in what is known as the Cold War.
Explanation:
The Truman Doctrine consisted in the provision of political, economic, and military assistance to any country that was likely or threatened to become communist, in order to counteract the Soviet Union. This doctrine was manifested for example in the Korean War.
And the Marshall Plan was a 12 billion economic assistance program to the nations of Western Europe, to help them rebuild after World War II, and keep them under the U.S. sphere of influence. This was particularly important because Eastern Europe was kept under Soviet Control after the war.
