Containment
A simple definition of containment is a policy that was designed to stop the spread of communism. We needed this because we didn't want the Soviet Union to get anymore power than they already have. If they were to get more power they could take over with a lot less fighting to get it.
The Soviets already made there way down to Bulgaria and were trying to take Turkey and Greece. In the picture to your right the green area represents the Nato members ( United States and Allies). The Orange area represents the Warsaw Pact ( Soviet Union and communism). Lastly the tan area is the countries who are considered Neutral.
The United States and our allies tried very hard to keep the Soviets from expanding. We used different policys, plans, and doctrines to prevent other counties to not fall in the communist trap.