The U.S. Park Police swept through McPherson Square early Saturday morning in an unannounced inspection of the Occupy DC camp, arresting four and ordering Occupiers to take down the massive "Tent of Dreams" beneath Gen. James McPherson's statue.

Occupiers had prepared for a showdown -- even forming a barricade around the "Tent of Dreams" -- but Park Police were quick to reassure protesters that they had no plans to evict them and merely wanted to check tents to ensure compliance with a camping ban in the park.

Still, Saturday's action, which continued into the afternoon, was the largest and most aggressive move the Park Service has made since announcing it would begin enforcing a camping ban Monday.

Dozens of officers on horseback, clad in riot gear, entered the park at about 5:30 a.m. and quickly set up barricades around most of the camp. A flyer passed out by officers warned protesters that this was their "last chance to come into compliance."

The ban prohibits sleeping in the park as well as preparing to sleep -- which means that bedding of any kind in tents is prohibited. The tents themselves are allowed to remain as symbols of the protest, although police removed several tents that had been clustered around Gen. McPherson's statue Saturday morning and arrested four protesters who refused to leave the circle.