SAN FRANCISCO - The start of war in Iraq (news - web sites) triggered one of the heaviest days of anti-government protesting in years, leading to thousands of arrests across the United States and prompting pro-war counter-demonstrations.
Slideshow: Anti-War Protests
Anti-war Protests Swell in Wake of Attack on Iraq
In San Francisco, police wearing helmets and carrying nightsticks arrested more than 1,300 people Thursday as a shifting mass of thousands of anti-war protesters commandeered the streets and paralyzed the evening commute.
Traffic was snarled in cities from Los Angeles to Washington, D.C., as anti-war protesters blocked off major intersections, some chaining themselves together. Scores of high school and college students walked out of class. In all, more than 1,800 people were arrested.
"The United States is acting in a completely aggressive way," said Howard Lisnoff, who donned a rubber President Bush (news - web sites) mask at a protest in Providence, R.I. and held a sign reading "War Criminal."
But the anti-war groundswell brought out thousands of counterdemonstrators, including 2,000 who gathered outside the state Capitol in Mississippi.
Marlena Puckett, who is engaged to a Marine in the war zone, fought back tears as she watched people waving American flags and carrying handmade signs with slogans like "God bless our troops" and "Let's roll."
Sheila Murphy attended a rally in Lincoln, Neb., where more than 200 people sang, cheered and prayed. "This is a time they need to know that everyone is behind the troops and supporting the troops," she said.
Though most of the anti-war rallies were peaceful, pockets of protesters in San Francisco scuffled with police, broke windows and heaved newspaper racks and debris into streets. Some protesters hurled rocks at trains, briefly halting service at a station in nearby Oakland.
"We went from what I would call legal protests to absolute anarchy," Assistant Police Chief Alex Fagan Sr. said.
One protester died after tumbling from the Golden Gate Bridge. Authorities were investigating the death as a possible suicide.
About 1,000 protesters remained on San Francisco's downtown streets late Thursday, vowing to shut down the city again Friday. Sirens and the whirring of helicopters rattled through downtown from dawn to dusk. Television video showed one man getting out of his car to throttle and punch several protesters.
In Portland, Ore., protesters smashed in three windows at a McDonald's restaurant, set a flag on fire and sprayed graffiti on a sign at a Shell gas station. More than 100 people were arrested.
"I like the idea of shutting down commerce and the city to counteract Bush's economic motives for this war," said Eric Anholt, 19, of Portland.
About 1,000 anti-war protesters demonstrated outside the West Los Angeles Federal Building, briefly clashing with police and forcing the closure of one of the city's busiest intersections at rush hour. At least 14 were arrested, and another 50 were arrested in Santa Rosa for blocking traffic.
Several thousand marchers snarled afternoon rush-hour traffic along Chicago's main arteries, repeatedly breaking through lines of police on horseback or in riot gear.
In Washington, D.C., dozens of activists temporarily shut down inbound lanes of a Potomac River crossing, holding up the morning commute. Outside the White House, about 50 shouted, "No blood for oil!"
Anti-war activists in Philadelphia blocked entrances to the downtown federal building, forcing police to detour motorists away from the area. More than 200 people were arrested in protests across Pennsylvania.
In New York, more than 300 protesters snarled traffic in Times Square during the evening commute. Police arrested 36 people.
Counterdemonstrators gathered alongside anti-war protesters in many places, shouting patriotic slogans and encouraging support of the president.
"The debate is over, we've had the debate," Robert Strickland, an Army veteran, said as he waved an American flag in Louisville, Ky. "It's time to rally around our troops and rally around our leaders."
Dennise Linville, 33, stood at the edge of a rally in Cleveland, with a placard declaring President Bush a hero.
"I have children and if this (Iraq) is not taken care of now, in five or 10 years they're going to be the ones who will have to go in the military and take care of it," Linville said.
Some anti-war demonstrators took pains to express their support for U.S. troops as they denounced the policy that sent them into Iraq.
"We support them so much that we don't want one to die in an unjust war," said Mike Slaton, who demonstrated in Louisville, Ky.
Students walked out of class at some high schools, while protests were held at several colleges.
At the Massachusetts Institute of Technology (news - web sites), in Cambridge, about 600 students converged on the student center, some chanting and wearing mock biochemical protective suits. A protest and sit-in at the University of California at Berkeley, led to 110 arrests.
In Texas, several hundred University of Texas at Austin students linked arms and sat down in a busy street. Police closed the area to traffic. Several hundred people blocked traffic in Asheville, N.C., and about 20 were arrested.
Nancy Parkinson, 62, who took part in a protest at the University of Florida, said she broke out her peace sign necklace and pink and lime green paisley shirt from her Vietnam protest days to show her support.
"I thought I would never have to wear it again," she said.
In St. Louis, as many as 1,000 anti-war protesters linked arms to form a human chain around the federal courthouse. Peaceful marches of about 2,000 people were held in Seattle and Madison, Wis.
Other demonstrations were solemn, with the reciting of Christian, Jewish and Muslim prayers through a bullhorn at a federal building in Pittsburgh.
In Des Moines, Iowa, about 400 people gathered Thursday night to pray for peace and the safety of all those touched by the war with Iraq. Joann McCracken, 50, of Des Moines, said it was a time of mourning.
"It's a sad, sad time for our country, for Iraq and really the whole world."