During the years 1947-1952 the Cold War, the anti- communist foreign policy of the U.S. government, and the reassertion by the American Communist party of its allegiance to the Soviet Union, the international communist movement, and a literal Marxist-Leninist ideology gradually gave rise to an anti-communist hysteria and to the repression and persecution of American Communists. Author Peter L. Steinberg shows that both the Truman Administration and the Communist Party were in part responsible for the McCarthy era that followed. Both were reacting to the ideologiical warfare conducted by J. Edgar Hoover. Using his allies in government, Hoover took advantage of the Cold War atmosphere to demand demonstrable action against communists. The Truman Administration responded with a loyalty program that seemed to legitimze the American people's worst fears, leading to demands for further action. The Communist Party's decision to "go underground" played into the hands of its enemies. Steinberg sees the attack on American communists as a necessary prelude to the demand for patriotic conformity and as a factor contributing to the development of an internal political police.