The military buildup that accompanied the Korean War took place in a highly charged political environment. Although Democrats had sat in the Oval Office since 1933 and had controlled Congress during all but two of the intervening years, a conservative coalition had also taken shape and had worked since the late 1930s to forestall liberal legislation on Capitol Hill. Despite a Democratic party resurgence in the election of 1948, and Truman's surprising defeat of the Republican challenger, Congress was increasingly deadlocked on domestic issues and the political climate had become more poisonous than ever.

The most toxic element in that poison was McCarthyism, named after Senator Joseph R. McCarthy of Wisconsin, a Republican conservative who made his reputation hunting Communist sympathizers in the federal government. McCarthy's brand of witch–hunting had been the stock–intrade of the Republican right wing since the last years of the New Deal. It had played a prominent part in the Republican party campaigns of 1946 and 1948, and had surfaced again in the violent political battles that culminated in the elections of 1950. One of those battles had involved the so–called McCarran Act, which required Communists to register with the attorney general and authorized the emergency detention of possible spies and saboteurs.