The establishment of a Communist government in China in 1949 and the North Korean invasion of South Korea in 1950 helped transform the Cold War into a global conflict, in which United States would confront Communism in Iran, Guatemala, Lebanon, and elsewhere.

In an atmosphere charged with paranoia and anxiety, there was deep fear at home about “enemies within” sabotaging U.S. foreign policy and passing atomic secrets to the Soviets. The discovery of a few cases of disloyalty fed such anxieties, and Senator Joseph McCarthy charged that many communists were active in high levels of government. McCarthy’s investigations uncovered little evidence of such activities and his popularity declined after the televised Army-McCarthy hearings.