The second Red Scare refers to the fear of communism that permeated American politics, culture, and society from the late 1940s through the 1950s, during the opening phases of the Cold War with the Soviet Union. This episode of political repression lasted longer and was more pervasive than the Red Scare that followed the Bolshevik Revolution and World War I. Popularly known as “McCarthyism” after Senator Joseph McCarthy (R-Wisconsin), who made himself famous in 1950 by claiming that large numbers of Communists had infiltrated the U.S. State Department, the second Red Scare predated and outlasted McCarthy, and its machinery far exceeded the reach of a single maverick politician. Nonetheless, “McCarthyism” became the label for the tactic of undermining political opponents by making unsubstantiated attacks on their loyalty to the United States. The initial infrastructure for waging war on domestic communism was built during the first Red Scare, with the creation of an antiradicalism division within the Federal Bureau of Investigation (FBI) and the emergence of a network of private “patriotic” organizations. With capitalism’s crisis during the Great Depression, the Communist Party grew in numbers and influence, and President Franklin D. Roosevelt’s New Deal program expanded the federal government’s role in providing economic security. The anticommunist network expanded as well, most notably with the 1938 formation of the Special House Committee to Investigate Un-American Activities, which in 1945 became the permanent House Un-American Activities Committee (HUAC). Other key congressional investigation committees were the Senate Internal Security Subcommittee and McCarthy’s Permanent Subcommittee on Investigations. Members of these committees and their staff cooperated with the FBI to identify and pursue alleged subversives. The federal employee loyalty program, formalized in 1947 by President Harry Truman in response to right-wing allegations that his administration harbored Communist spies, soon was imitated by local and state governments as well as private employers. As the Soviets’ development of nuclear capability, a series of espionage cases, and the Korean War enhanced the credibility of anticommunists, the Red Scare metastasized from the arena of government employment into labor unions, higher education, the professions, the media, and party politics at all levels. The second Red Scare did not involve pogroms or gulags, but the fear of unemployment was a powerful tool for stifling criticism of the status quo, whether in economic policy or social relations. Ostensibly seeking to protect democracy by eliminating communism from American life, anticommunist crusaders ironically undermined democracy by suppressing the expression of dissent. Debates over the second Red Scare remain lively because they resonate with ongoing struggles to reconcile Americans’ desires for security and liberty.