Shortly after arriving in the US in 1882 Johann Most published a pamphlet entitled The Science of Revolutionary Warfare: A Manual of Instruction in the Use and Preparation of Nitroglycerene, Dynamite, Gun-Cotton, Fulminating Mercury, Bombs, Fuses, Poison, etc, etc. This provided a slant to American anarchism different from the philosophical one of Thoreau, Emerson and Whitman. It was nowhere more apparent than in Chicago, where industrial relations were bitter, the police were brutal, and armed resistance in general and dynamite in particular were advocated daily. About half the 6,000 or so anarchists in America were in Chicago, most of them Germans and Czechs.

In May 1886, when the unions were calling for an eight-hour day, the McCormick Harvester Factory locked out 1,400 workers without warning. Fighting broke out, the police fired on the strikers, killing several and wounding more. The next day a protest meeting in the Haymarket Square was breaking up peacefully when police arrived in numbers. A bomb was thrown and guns were fired on both sides. Seven policemen were killed, 70 wounded; casualty figures for the demonstrators were probably three...