The end of World War II saw the rise of a bi-polar world, divided between the capitalist (often called "free") West and communist East. The fear of communism developed because of actions taken by Joseph Stalin immediately after the war. He refused to withdraw troops from East Germany, claiming that the U.S.S.R. needed a "buffer" to prevent further attacks. Thereafter, he instituted puppet governments in much of Eastern Europe in violation of the Yalta agreements.
The aggressive nature of Stalin's actions led many to conclude that the Soviets intended to take over the world. This was an easy conclusion to reach since many communists spoke of a "world wide revolution." Among the many responses was the development of an "anti-communist" philosophy. Most people knew that communism was atheistic; as a result the words "under God" were added to the Pledge of Allegiance; and "In God We Trust" was added to American currency. Americans attended churches in droves, not from religious conviction but as a public response to the perceived threat. A popular movie, "My son, John" warned of communist infiltration. The McCarthy hearings, were of course a more drastic response to the perceived communist threat.
During the Eisenhower administration, newspaper ads often depicted Soviet Premier Nikita Khrushchev with a finger pointed upward stating "we'll bury you." Americans supported radio broadcasts of western news and propaganda into Eastern Europe known as Radio Free Europe.
Of course, the greatest development was the arms race. As soon as it was determined that the Soviets had access to nuclear weapons, the race was on. In addition to the race, Americans were encouraged to build bomb shelters and air raid test signals were heard over many cities at designated times. All of this was the result of the fear of a communist attack or takeover.