The Red Scare was a national fear of leftist movements, especially communism. The first Red Scare from 1917 to 1920 occurred in response to the Russian Revolution and subsequent communist revolutions.
The second Red Scare, also known as McCarthyism, was a communist witch hunt from 1947 to 1957. In both cases, the United States enacted measures to crack down on communism. The Red Scares marked the federal policy to outlaw communism in the United States. Thousands of federal employees were terminated for being suspected as “Un-American”, creating an atmosphere of fear and paranoia.