What event illustrated the U.S. policy of containment during the Cold War?

The Korean War is a significant illustration of the U.S. policy of containment during the Cold War. This policy aimed to prevent the spread of communism beyond its existing borders, originating from the belief that if one country fell to communism, neighboring countries would follow—often referred to as the "domino theory."

When North Korea, backed by the Soviet Union and China's communist government, invaded South Korea in June 1950, the United States and other members of the United Nations intervened militarily to support South Korea. This military action was motivated by the desire to contain the spread of communism on the Korean Peninsula and was a clear demonstration of the U.S. commitment to this policy. The U.S. sought to limit the expansion of communism through direct military involvement, marking a significant escalation in its Cold War confrontations.

The other options also relate to events that reflect U.S. foreign policy during the Cold War but do not exemplify containment in the same direct manner as the Korean War. For instance, the Vietnam War involved attempts to assist a government fighting against communist forces but evolved from the earlier situation rather than being the initial response to aggression. The Cuban Missile Crisis was a confrontation showcasing the tension and brinkmanship between the U.S.