Answer: firmly opposing Soviet expansion and keeping communism in check.
Explanation: The key principle of the policy of Containment was a United States of America idea of using numerous strategies to halt the spread of communism. This policy was a response to the various moves adopted by the Soviet Union to increase its communist sphere of influence in Eastern Europe, China, Korea, and Vietnam. The goals of containment Policy was to keep communism from spreading to other countries. The truman doctrine was the policy of the United States of America to support free peoples who are resisting soviet pressures to adopt communism.