What did the containment strategy provide a rationale for?

The Containment Strategy was the principal strategy adopted by the US in foreign policy matters during the Cold War era.

It aimed to stop the expansion of the national enemy: communism, and in turn, of the URSS and the countries under its influence, that were denominated the Eastern Bloc. It consisted on responding to any attempt of expansion performed by the URSS, seeking to spread communism in Eastern Europe, Korea, China Africa, Vietnam, and Latin America.