DENVER -- There's one good reason that most protests didn't cause trouble during the Democratic National Convention, Denver's police chief says: Demonstrators kept in touch with officers -- by cell phone.

Police Chief Gerald Whitman said his force spent months making contact with all but one leader of the groups that descended on Denver this week. During their protests, the leaders of these groups had the phone number of a police liaison officer assigned to them so that they could continually update their plans. And police had their cell numbers.

"Do you plan on getting arrested?" these officers would ask them as they marched.

"Some of them will actually say, 'Yes, we plan an action and yes, we want to be taken into custody,'" Whitman said in an interview.

The system worked Wednesday, when Iraq War veterans spilled out of a rock concert and led more than 3,000 people on a 4-mile march without a permit to the Pepsi Center, home to the first three days of the convention. March handlers kept police advised of their moves, and no one was arrested.

"We had built an amazing rapport with the police," said an ecstatic Matthis Chiroux, 24, an organizer with Iraq Veterans Against the War.

It was just part of a convention security plan, led by the Secret Service, that included calling in at least 1,000 uniformed officers from around the metro area and horse patrols from out of state. The federal, state and local law enforcement presence was nothing short of overwhelming.

Leading up to the Democratic and Republican conventions, security agencies had information about militant anarchist groups stockpiling commercial fireworks, modified shields, batons, helmets, gas masks, iron spikes and other weapons, according to an Aug. 22 Homeland Security intelligence assessment obtained by The Associated Press.

"Their intent is not to harm people, but to incite civil disturbances and property destruction at the venues and other locations associated with the conventions," the assessment said.

A few anarchist groups -- including Recreate 68 -- planned to use a tactic known as "Black Bloc" to destroy property or divert law enforcement, according to the assessment. The tactic involves vandalism, rioting and street fighting.

"The protesters have actually told us that they're going to damage property. So when they line up and head for downtown, we're thinking that's probably what they're going to do," Whitman said.

Denver's largest batch of arrests happened Monday night, in front of the Civic Center, when police met a group armed with rocks and bags of urine blocking a street near a municipal building, he said.

Unlike New York's 2004 Republican National Convention, when police responding to similar situations cordoned off entire blocks with orange netting and arrested everybody inside, Denver officers gave many people the chance to leave before moving in.

"We only made 91 arrests at the scene, but there were maybe six times as many people there," Whitman said. "So the people we arrested were on the street, wouldn't get out of the street. They locked their arms, we told them again (to leave), they obviously wanted to be arrested."

On Sunday, protesters threw wooden slats and other debris at police from a downtown parking garage. Officers simply lined the streets and waited them out. After about 45 minutes, a boisterous crowd left a nearby intersection. Police were unable to find those inside the garage.

On numerous occasions, police encountered groups ranging in size from three to the hundreds with enough force to show any engagement would be a losing proposition.

Whitman said Denver's security plan was similar to Boston's Democratic National Convention plan in 2004, when police took a non-confrontational approach and arrested only six people.

"What's the penalty for blocking a sidewalk or parading without a permit? Why initiate a confrontation when it's only a misdemeanor or a fine?" said Boston police Superintendent in Chief Robert Dunford, who was in charge of convention security in 2004.

"I think it's the way to go," Dunford said. "Most people come in with a legitimate reason to protest and aren't looking for competition with the police, and we need to strike a balance between their First Amendment Rights and security."

Not all ran smoothly. Police are investigating an incident in which video shows an officer using a baton to push a woman to the ground. And ABC News protested the arrest of a producer on trespass and interference charges while he was reporting outside the Brown Palace Hotel.

Denver authorities had set up a detainee processing center at an old city warehouse, anticipating mass arrests. But by week's end there were only 152 arrests.

"The performance measure isn't how many people are or aren't arrested. More than that, it's whether they were able to respond to every situation that occurred, if they responded quickly and appropriately. That's what they'll measure themselves by," said Dave Wilkinson, a retired Secret Service agent who headed security preparations for the 2004 G-8 summit at Sea Island, Ga.

A vast majority of Denver residents and visitors were thankful for the security blanket.

"It sort of felt and looked like New York did right after 9-11," said Jennifer Rothgeb, a convention volunteer from Annapolis, Md., as she boarded a shuttle bus on the downtown 16th Street Mall.

"It's a bit overwhelming, but if it keeps everything safe, then I guess it's worth it."