On this day in 1971, President Nixon executed "Operation Garden Plot", deploying 10,000 federal troops in Washington D.C. to suppress Vietnam War protests, leading to the largest mass arrest in U.S. history - 12,614 people in total.

The 1971 May Day Protests were a series of large-scale civil disobedience actions in Washington D.C. in protest against the Vietnam War. They began on May Day of that year and continued with similar intensity into the morning of May 3rd.

The protest began when 35,000 people camped out in West Potomac Park near the Washington Monument park to plan for the coming protest. The next day, the Nixon administration canceled the protesters' permit and police, dressed in riot gear, raided the encampment, firing tear gas and knocking down tents.

On May 3rd, President Nixon executed "Operation Garden Plot" (a plan developed during the 1960s to combat major civil disorders), deploying 10,000 federal troops to various locations in the Washington D.C. area.

While the troops secured the major intersections and bridges, police roamed through the city, making massive arrest sweeps and using tear gas. By eight in the morning, police had detained over 7,000 people, arresting anyone who looked like a demonstrator, including construction workers who had come out to support the government.

Over the course of several days, the city arrested 12,614 people, making it the largest mass arrest in U.S. history. Members of the Nixon administration would come to view the events as damaging, because the government's mass arrests of protesters were perceived by the public as violating citizens' civil rights.