What caused the Red Scare after World War II?

Question

The U.S. government wanted to monitor the activities of anyone with left-leaning political beliefs.
The U.S. government wanted to end opposition to the war in Vietnam quickly.
The U.S. government wanted to prevent spying by the Soviet Union during the Cold War.
The U.S. government wanted to weaken groups with right-leaning political beliefs.

Answer 1

The primary cause of the Red Scare after World War II was the U.S. government wanting to prevent spying by the Soviet Union during the Cold War.

After the war, there was widespread fear of communist influence and espionage, particularly in light of events such as the Soviet Union's atomic bomb test in 1949 and the revelation of espionage cases like the Rosenbergs. This created an atmosphere of suspicion and paranoia regarding both actual and perceived communist sympathizers within the United States. As a result, government actions, such as those led by Senator Joseph McCarthy, sought to root out alleged communists and leftist individuals from various institutions, including the government, entertainment industry, and labor unions.

While there were various motivations and underlying tensions, the overarching fear of communism and the Soviet threat were the main drivers of the Red Scare during this period.