The Red Scare after World War II was primarily characterized by a pervasive fear among Americans regarding the potential for communist infiltration and espionage within the United States. This fear was largely a reaction to the geopolitical climate of the time, particularly the rise of the Soviet Union as a superpower and the spread of communism in Eastern Europe. The U.S. government and the public were alarmed by the possibility that communist ideology could influence American society and that Soviet agents might be operating within key institutions. This led to a series of investigations, blacklisting of suspected individuals, and widespread paranoia about communist sympathies, significantly impacting American politics and society during the Cold War.