The Red Scare of 1920s was fueled by the fear that

The first red scare was fueled by the fear of far-left extremism.

An event that caused this fear was the Bolshevik Revolution in Russia, and the spread of "communism" and anarchism to the United States. Several immigrants who had these self proclaimed communist ideas were arriving in the US. So, there were large raids that were intended to seek out those radicals.

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The Boston Police Strike in September 1919, contributed to fears that radicals intended to spark a revolution.

On April 15, 1921, two employees, Nicola Sacco and Bartolomeu Vanzetti were arrested for murder and robbery. The two maintained their innocence in the trial, however, they were anarchists and socialists. They were found guility in less than two weeks after their arrest, and put to death on the 27th.

b: to eliminate competition from other farmers