But the pillow fight held August 20 got rough, with 30 members of the class of 2019 requiring medical attention and 24 suffering concussions, Caslen said in a statement.

Other injuries included a broken nose, a dislocated shoulder, and a hairline fracture of a cheekbone, he said. All the students have returned to duty.

Caslen didn't say how the injuries occurred but that an investigation has been started.

The New York Times, which broke the story, reported some plebes swung pillow cases containing hard objects.

A video posted on YouTube showed several hundred students pouring into a courtyard and swinging pillowcases in a disorganized manner.

"While these spirit events do occur, we never condone any activity that results in intentional harm to a teammate," he said. " Although the vast majority of the class appears to have maintained the spirit of the event; it is apparent that a few did not."

Medical personnel will follow up with the injured students, he said.

Caslen also said he takes full responsibility for the pillow fight. "We remain committed to the development of leaders of character. We will continue our investigation, ensure accountability, and reinforce with the Corps that we must all take care of our teammates."