100,000 people march on the Pentagon - Oct 21, 1967 - HISTORY.com

Demonstrators including radicals, liberals, black nationalists, hippies, professors, women’s groups, and war veterans march on the Pentagon.

The rally in front of the Lincoln Memorial started peacefully, though Dr. Benjamin Spock—baby specialist, author, and outspoken critic of the war—did call President Johnson “the enemy.” After the rally, the demonstrators, many waving the red, blue, and gold flag of the Viet Cong, began marching toward the Pentagon. Violence erupted when the more radical element of the demonstrators clashed with the soldiers and U.S. Marshals protecting the Pentagon.

The protesters surrounded and besieged the military nerve center until the early hours of October 23. By the time order was restored, 683 people, including novelist Norman Mailer and two United Press International reporters, had been arrested. This protest was paralleled by demonstrations in Japan and Western Europe, the most violent of which occurred outside the U.S. Embassy in London when 3,000 demonstrators attempted to storm the building.