In the Soviet Union and the Eastern Bloc
Gradually, the leaders of the non-Communist parties were removed, either by discrediting or intimidation, or by political trials followed by imprisonment or even execution.
The bloc was the scene of numerous political trials in all sympathetic countries against people accused of being "Titoists" (a term that comes from Tito, leader of Yugoslavia), accused of deviating from Moscow policy, nationalism or Zionism, or working for the West.
Very many people were imprisoned or executed, the vast majority quite simply because they bothered the regimes then in place while several of them were authentic communists like László Rajk who in Hungary was one of the first victims with 19 other men from these great purges in 1949.
In the United States
In the United States, between 1950 and 1954, the Republican Senator from Wisconsin, Joseph McCarthy, led a veritable hunt for "Reds", alongside institutions such as the House of Representatives Commission of Inquiry into Un-American Activities (House Un-American Activities Committee or HUAC). He had all those he suspected of being members of the Communist Party, "fellow travelers" or simple sympathizers, impeached pell-mell:civil servants, artists, intellectuals, scholars and politicians.
Secretary of State Dean Acheson was suspected of being "soft on communism" and George Marshall, the former secretary of state, accused of having abandoned Chiang Kai-shek in 1946. Ethel and Julius Rosenberg, an American Jewish couple, were arrested, sentenced to death and executed for allegedly providing information about the nuclear bomb to the Soviets. This case aroused great emotion in Europe, and especially in France, where the climate of collective hysteria which had surrounded the trial was denounced. However, it now appears that, according to KGB records, the Rosenbergs, at least the husband, are guilty, they will be the only spies executed after being put on trial in the West during the Cold War.
Finally, in 1954, McCarthy overstepped the mark and questioned the loyalty of the army. He was then the object of a reprimand on the part of his colleagues in the Senate:it was the end of McCarthyism.