The red scare following ww1 was caused primarily

The Red Scare was primarily caused by a fear of communists, socialists, anarchists, immigrants, and radical labor groups that were developing in industrialized nations at this time.

The red scare following the World War I was primarily caused by the fear of communism, socialism, anarchists, immigrants, and racial labor that has been developing and growing in the industrialized nations, especially in the United States, during the 1920s.