Many covered themselves with sheets designed to make them resemble dead bodies.
"I had to bring my body down here to say no," Paki Wieland, 63, of Northampton, Mass., said as she waited in line to get on a police bus.
The protest was organized by Declaration of Peace, a coalition of about 500 groups that has organized war protests around the country during the past week. The events started Sept. 21, to coincide with the United Nations International Day of Peace.
Protesters started their demonstration in a park and marched along the street in front of the Capitol carrying 20 mock coffins draped in American flags or black cloth.
Today's protest follows on the heels of the arrests of 71 religious leaders and activists at the Hart Senate Office Building on Tuesday for civil disobedience against the Iraq war.
CBS News reports that three women were removed from the House Chamber and arrested after causing a disruption while members were debating the Military Tribunal bill, which passed 253-168.