Defiant Occupy Boston protesters were arrested and charged with unlawful assembly and being in a public park after hours in a massive, early morning crackdown at the protest group's second tent city on the Rose Kennedy Greenway.

"It's important that we gain control and make sure the rules are followed, " said Boston Police Commissioner Edward Davis, who was on site during the police action.

The protesters tents and personal belongings were also tossed into the trash during the sweep that kicked off at about 1:30 a.m. and included about 100 arrests.

The arrests and site eradication came after as many as 700 police officers descended to the Atlantic Avenue compound, which a small faction of protesters had taken over yesterday, while Boston police were busy keeping thousands more protesters off the Charlestown Bridge.

Davis acknowledged that the arrests marked a shift in the once harmonious relations between the group and the police.

"The group that was here for the first ten days was working very closely with us," Davis said, "but they warned us yesterday morning that a new group, the anarchists, wanted to take control."

By nightfall, at least 40 tents had been pitched on this second site, which is just north of the group's original occupation site.

Boston police and Mayor Thomas M. Menino asked the leaderless group, which is rallying for a more equitable tax structure in the U.S., to leave that second site by midnight.

Police said the park's patrons had just spent $150,000 to spruce it up.

Protesters refused to move.

As midnight came and went, the 300 occupied stayed there, chanting, singing and delighting in their staying power.

"Mayor Menino told us to leave by midnight," one of the occupiers shouted as the rest of the group cheered. "It's 1 a.m, and we're still here."

A wave of police arrived on site just after 1:30 a.m.

Officer from the Boston police, the state police, the transit police and the Suffolk County sheriff's office arrived on foot, by motorcycle, in prisoner transport wagons, and on bikes.

Police then surrounded the second campsite, told protesters the park was closed to the public at 11 p.m., and asked them to leave.

When the protesters stayed, police began pulling them, one by one, from the crowd.

"They just ripped the group open, and went for our tents," said Nicholas Hassell, a 21-year-old grill cook from Franklin. "They shouldn't be doing this. We have the right to exercise our freedom of speech."

Protester Anasstassia Baichorova, 27, and from Cambridge, also criticized police.