Final answer:
The term 'Red Scare' refers to the period of intense fear and paranoia in the United States surrounding the threat of communism and anarchist ideologies, particularly after World War I and then again after World War II during the early years of the Cold War.
Step-by-step explanation:
The national hysteria that gripped the nation in regards to communism is known as The Red Scare. The Red Scare was a period of intense fear and paranoia concerning threats posed by anarchism and Communism, particularly between 1919 and 1920. This fear was exacerbated by events such as a series of thirty-six letter bombs discovered at a New York City post office and the simultaneous explosion of bombs on June 2, 1919.
The fear and distrust extended to encompass socialists, Communists, members of the Industrial Workers of the World (Wobblies), and anarchists as threats to the United States. In the 1920s, the trial of Italian immigrants Sacco and Vanzetti became emblematic of this national fear of foreigners and radicals during the peak of the Red Scare. Furthermore, despite the American Communist Party's relatively small size after World War II, the discovery of evident espionage activities, including ones related to the Manhattan Project, fed into the second wave of Red Scare paranoia.