What was the significance of the executions of Nicola Sacco and Bartolomeo Vanzetti?

Sacco and Vanzetti were charged with the crime of murder on May 5, 1920, and indicted four months later on September 14. Following Sacco and Vanzetti's indictment for murder for the Braintree robbery, Galleanists and anarchists in the United States and abroad began a campaign of violent retaliation.