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Tensions between protesters and police heightened Saturday night on the eve of the NATO summit of world leaders, with helmeted police at an evening march using their nightsticks and bicycles to fend off surging demonstrators.

During a march that began in the West Loop but wound its way downtown, a female protester tried to take an officer’s bike at Balbo Drive and Wabash Avenue. When an officer grabbed her, other protesters tried to free her. As the crowd surged toward the officers, at least one officer took out a baton and struck a protester. Another officer pushed a protester to the ground.

It was among the first major incidents in two days of protests leading up to the Sunday opening of the NATO conference, being held for the first time in a U.S. location other than Washington. Late Saturday, with police and protesters still on the street, it wasn’t clear when or how the night would end.

Chicago police Superintendent Garry McCarthy, who walked with other commanders at the tail of the march, said that for all the flare-ups late in the day, “it’s not too bad.”

During several marches, police were able to steer the direction of protesters, which frustrated some demonstrators.

An evening march that began on the West Side featured a few hundred protesters who tried to get ahead of police patrols by sprinting. Officers on bicycles sped along the street to keep up with them. But the protesters grew winded and slowed.

Later, at State and Washington streets, the protesters were met by a line of helmeted officers with their face shields down. A confrontation broke out as protesters tried to push through the line and police pushed back.

“Do not retreat,” one marcher shouted to her colleagues. “Stand your ground.” At least three protesters were detained before police allowed marchers to continue south on State.

Tensions weren’t as high earlier Saturday. In the afternoon, after holding a solidarity rally at Daley Plaza on behalf of three out-of-state men facing state terrorism charges, hundreds of protesters marched along State Street in the downtown theater district.

As the crowd chanted, Eddie Villareal and his fiancee, Patty, stood bewildered in their wedding attire outside the Chicago Theatre taking pictures before their 6 p.m. wedding.

“It’s not what we expected, but it’s pretty exciting,” Patty said as several protesters shouted words of congratulation. “We’re glad to celebrate it with all of you.”

Police steered the afternoon protesters from Wacker Drive onto southbound Michigan Avenue. After a brief standoff at Michigan and Congress, police allowed the march to continue south. When marchers tried to turn west onto 18th Street, two blocks from the 1st District police headquarters, police used bikes to stop them. In a confrontation, one man was taken away in handcuffs.

Unlike Friday, when anti-NATO protests began in earnest, police, as of 9 p.m. Saturday, were able to keep marchers from crossing the Michigan Avenue bridge over the Chicago River, the gateway to the Magnificent Mile and its posh retailers. That’s also where many NATO dignitaries are staying.

The protests started Saturday morning. Mayor Rahm Emanuel’s planned cuts to mental health clinics prompted protesters to converge in front of the mayor’s Ravenswood home at midday. Police told demonstrators they could not stop in front of the residence and had to keep moving. That resulted in hundreds sitting in the middle of Hermitage Avenue, one house north of the mayor’s home.

Eventually, a smaller group splintered off and stopped for about five minutes in front of Emanuel’s home. Wearing hospital gowns over their clothing, group members unfurled a banner saying “Healthcare not warfare” and chanting “This is what democracy looks like.”

Some of the protesters took photos of themselves making peace signs, using the mayor’s home as a backdrop. Others stood in front of police lines, holding their protest signs and posing for photos.

The bulk of the crowd dispersed into groups on Lincoln Avenue, Irving Park Road and other nearby streets, sporadically stopping at intersections to sit. A few stragglers stayed behind and taunted one of the mayor’s neighbors as he sat on his porch with his black Labrador.

“I need to talk to Rahm about justice and stuff,” one woman yelled. “Your neighbor has killed health care and you still live beside him?”

Saturday’s marches were impromptu. The largest organized rally against the military alliance is scheduled for Sunday, a march from the Petrillo Music Shell in Grant Park to Michigan Avenue and Cermak, outside the edge of McCormick Place.

For two days, Chicago police had taken a bend-but-not-break approach to containing NATO protesters in a test of physical and mental stamina.

From the mayor’s neighborhood to the streets of the Loop, a long blue line of police on bikes and on foot had guided, herded and diverted a near continuous series of marches all day Saturday.

Using methods they practiced on the streets since a May Day protest and at smaller marches all week, police shifted and rolled with the marchers. Officers on foot lined the sidewalks while dozens of cops on bicycles fanned out. Some of the cycling officers rolled alongside the protesters while others darted in front to form wheel-to-wheel barricades at intersections.

Never far away was the real muscle of the police force — officers with batons in black garb, and white vans of officers in riot gear who maneuvered to hot spots to provide backup. The more heavily clad officers remained in the background, for the most part, emerging only when situations got tense.

In the middle of the Loop, several protesters were detained after a police officer was knocked over, and heavily clad officers moved in to assist the bike patrol that had guided the march for hours.

Protesters got a similar full treatment earlier Saturday when they tried to repeat their Friday maneuver of crossing the Michigan Avenue bridge, which resulted in a scrum with police in the middle of the bridge.

As a few hundred protesters approached the bridge Saturday from Wacker Drive, police were waiting in three-deep wedge of bikes. Protesters paused only briefly before turning south on Michigan and avoiding confrontation.

It was clear police had put a premium on keeping marchers off the Magnificent Mile through the city’s premier shopping district.

As protesters slowed late in the day on one of their many circular journeys, Chicago Police Chief Debra Kirby, head of the department’s international relations office, was on the scene to monitor the march.

Asked how far police would let the crowd go, she said, “Till they tire out.”

Police on bikes were leapfrogging the march, moving forward to block the middle of the street and keep the protesters in the northbound lanes and away from retail shops.

Tribune reporters Rick Pearson, David Kidwell, John Byrne and Dan Hinkel contributed.

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