Unlike most of the counterdemonstrators in Charlottesville and elsewhere, members of antifa have shown no qualms about using their fists, sticks or canisters of pepper spray to meet an array of right-wing antagonists whom they call a fascist threat to American democracy. As explained this week by a dozen adherents of the movement, the ascendant new right in the country requires a physical response.

“People are starting to understand that neo-Nazis don’t care if you’re quiet, you’re peaceful,” said Emily Rose Nauert, a 20-year-old antifa member who became a symbol of the movement in April when a white nationalist leader punched her in the face during a melee near the University of California, Berkeley.

“You need violence in order to protect nonviolence,” Ms. Nauert added. “That’s what’s very obviously necessary right now. It’s full-on war, basically.”