Chanting "peace, peace, peace," the protesters marched to the convention center where President Barack Obama and dozens of other world leaders met to discuss Afghanistan. At least 10 of the veterans threw down their medals in the street in protest, the Tribune said.
"If I want to contine to live with integrity, I must get rid of this," Erica Sloan, from Ohio, of the U.S. Air Force, told the newspaper.
At one point, a group of protesters dressed in black linked arms and tried to break a sidewalk police line, with some throwing water and a stick from a protest sign at the police. But police pushed them back, keeping them in the street, and after a tense few minutes, the protesters marched ahead.
Police said they arrested a Wisconsin man on Saturday evening after he was found with shotgun shells, knives and a gas mask.