First rule of far-right fight clubs: Be white and proud

To Mr. Chapman, 41, who on social media goes by the nom de guerre Based Stickman — “based” is slang for not caring what others think, and “stickman” refers to the closet dowel he wielded this spring at his first political skirmish — the Alt-Knights are a frustrated brotherhood of right-leaning soldiers conscripted to do battle with the left and devoted, as he put it in a Facebook post in April, to “defense and confrontation.”

“There’s been a lot of organized violence on the part of the left against the right, so we have to organize,” Mr. Chapman said. “The purpose is to have a peaceful event. But if people are attacked, you have to be ready and willing to defend yourself and your right-wing brothers and sisters.”

This form of aggression is something researchers say they have not seen on such a scale before on the far right, where the chosen method of provocation for groups like neo-Nazis and the Ku Klux Klan is to demand the use of public space for rallies where they can spew racist and offensive language that is nonetheless protected as free speech.