The Red Scare
In the United States in the mid-20th century, public sentiment towards the Soviet Union and towards communism was very hostile. Among other things, this sentiment stemmed from a real fear that a Soviet-backed communist coup d’état could topple the U.S. government, with death camps, limitations to civil liberties and expropriation of private property as a consequence. Opportunistically though, in American political discourse, threats were frequently exaggerated and fear was often exploited in various ways for personal, political and economic gains.
Suspected communists investigated
One way of exploiting public fear of communism was to accuse political opponents and personal rivals of being communists. Such accusations habitually prompted state-led investigations, and seemingly unfairly, almost regardless of the outcome of the investigations, branded the accused as Soviet sympathizers. A reputation of being a Soviet sympathizer, in turn, often resulted in social ostracism and unemployment, meaning that accusing others of communist affiliations was an effective way of dragging people through the mud.
Innocent people dishonored
State-led investigations of suspected communists reached its climax in the 1950s. Only occasionally though, would the intelligence agencies capture real Soviet spies or others involved in criminal activity. Instead, more often, the investigations led to innocent people having their reputations and lives ruined, which is why the persecutions are generally deemed witch hunts today. People with left-leaning political opinions were especially at risk of these smear campaigns and false accusations, but practically anyone could be targeted.
Because the color representing both communism and the Soviet Union is red, the post-war period of anti-communist frenzy in American history is known as the Red Scare. Making lightly substantiated incriminating accusations, furthermore, became known as McCarthyism after Senator Joseph McCarthy, the most famous accuser of the era.