How is the Korean war an example of U. S. containment policy ?

Containment as one of the elements of Cold War policy.

Explanation:

This is a policy that the United States pursued continuously during the Cold War. Restriction in this con implied an effort to limit the spread of the ideas of communism globally. In this case, North Korea proclaimed the ideas of communism and was supported by the Soviet Union. The policy of restriction by the United States implied attempts to spread communist ideas to states that had not been communist until then. The United States did not seek to abolish communism in countries where it already existed as a political system.