The social unrest that followed World War I coincided with the founding of the Communist party and precipitated the first wave of explicit anticommunism, the red scare of 1919-1920. This crackdown, like earlier outbreaks of political repression, focused on foreigners and labor unions. Immigration officials rounded up and tried to deport thousands of foreign-born radicals, and many employers used red-baiting to break strikes. The repression succeeded, and, during the 1920s, neither the American Communist party nor the rest of the Left had any significant influence.

But in the following decade, the onset of the Great Depression and the rise of Adolf Hitler spurred the party's growth. In accordance with an international Communist policy known as the Popular Front, the party tried to create a broad coalition against fascism. By muting its revolutionary rhetoric and supporting President Franklin D. Roosevelt and the New Deal, it attracted many middle-class idealists. Others joined the party to organize labor unions or stop Hitler. As a result, it was easy for right-wing opponents of the social changes of the 1930s to attack them as a Communist plot. But such charges had little impact. Many Americans, though never tempted to become Communists themselves, nonetheless tolerated the party.

That toleration disappeared in 1939 when, as a result of the Nazi-Soviet pact, the Communist party opposed Roosevelt's foreign policy and the Popular Front disintegrated. Liberals, who until then had defended Communists against the Right, turned against the party themselves, transforming anticommunism into a more widespread enterprise. Labor unions, universities, private organizations, and governments at every level ousted Communists from their ranks. A broader purge would certainly have occurred had Hitler's invasion of Russia in June 1941 not changed the Soviet Union into an American ally.

The coming of the cold war resuscitated domestic anticommunism and made it central to American politics. Because of the Communist party's connection to the Soviet Union, it was now seen as a threat to national security. A consensus developed based on several key assumptions: that all Communists owed their primary loyalty to Moscow; that they unblinkingly followed the party line; and that they would, whenever possible, work to subvert the American system. There was just enough substance to these charges to make it possible for this otherwise unrealistic image of American Communism to gain currency and fuel the demand for its exposure and elimination.

Although the campaign against communism took place on every level, the most effective initiatives came from the federal government. In 1947, the Truman administration promulgated a loyalty-security program that barred Communists or people who associated with Communists from government jobs. At the same time, the Department of Justice brought criminal prosecutions to bear on the party. It tried to deport foreign-born Communists and, in 1948, indicted and convicted the party's top leaders under the Smith Act, a 1940 law prohibiting the "teaching and advocating" of subversive doctrines. Several hundred Communists went to jail. Congressional committees, especially the House Un-American Activities Committee huac, investigated supposed Communist subversion throughout American society. The Supreme Court, despite the serious constitutional issues involved, placed few restrictions on the anticommunist campaign. This official activity legitimated a witch-hunt. Politicians, abetted by sympathetic journalists and other interested parties, used the charge of Communist infiltration to implement agendas that often bore little or no relation to national security.

As the anticommunist campaign spread, the civil liberties of many people were threatened. This occurred primarily because of the widespread belief that communism so endangered the nation's security that the rights of individuals, especially of those supposed to be Communists, could be ignored. The structure of the anticommunist campaign, with its two-stage procedure of first exposing and then punishing alleged subversives, diffused responsibility for the repression. Official authorities like huac and the fbi usually handled the first stage by identifying the tainted individuals, and employers usually handled the second by firing them.

The party's insistence on secrecy made the exposure of its members the central feature of the anticommunist crusade. Because Communists had been part of a larger political movement that encompassed an entire constellation of left-wing causes and organizations, investigators assumed that all participants in the larger movement belonged to the party as well. Reactionary and overzealous investigators expanded the definition of what constituted a communist activity until it came to include anything from appreciating the paintings of Pablo Picasso to speaking out for the Bill of Rights.

Anticommunism was used for partisan purposes as well. The Republican party sought to capitalize on a few cases of alleged Communist infiltration of the New Deal. Ambitious politicians like Joseph R. McCarthy asserted that the Democrats had been "soft" on communism and had "lost" China after the war. There was no truth in these charges, but they put the Democrats on the defensive and, especially after the Korean War broke out in June 1950, made them afraid to challenge the anticommunist crusade and the abuses that accompanied it.

By the late 1950s, the furor had subsided. Zealots and opportunists like McCarthy had given anticommunism a bad name. And it was clear that the enfeebled and internally divided Communist party was no threat to national security. But the crusade had taken a toll. Not only had thousands of people lost their jobs, but political dissent had almost disappeared - an ironic result at a time when the United States was combating communism throughout the world in the name of freedom and democracy.