A Human Rights Watch report claims that has created "an atmosphere of impunity in which many soldiers feel they can pull the trigger without coming under review".
The 82nd Airborne in Fallujah was singled out.
Fallujah was one of the last places in this part of Iraq to be taken over by conquering U.S troops and initially it offered them the least resistance.
And then, something went wrong.
"I counted more than 177 rounds hitting this north wall, and over a 30-yard area. I believe that there was a disproportionate response by the 82nd Airborne," says Fred Abrahams, of Human Rights Watch.
But that's how they are allowed to respond to anyone defined as "hostile."
"It is our mission, and it is within rules of our rules of engagement, to pursue that hostile force until he either surrenders, is defeated or destroyed," says U.S. Cmdr. Gen. Ricardo Sanchez.
The 82nd Airborne is a highly trained combat unit. And therein may lay the root of problem.
"Take a soldier and try to make him a policeman overnight ... it's a difficult job for a trained policeman to do, let alone a soldier who is not completely trained in such operations ... so we're asking them to do pretty much the impossible," sayd retired Col. Mitch Mitchell, a CBS News military analyst.
But the military already knew that. In Afghanistan, Special Forces soldiers complained combat troops undermined their hearts' and minds' efforts.
"Since the 82nd got here, the whole attitude has changed around here, they're throwing rocks at us now," says "Skip," a Special Forces officer. "Before they used to cheer and laugh."
The 82nd came to Fallujah expecting trouble.
"They hype it up a lot and they make it sound worse than it really is," says Sgt. Cody Trobaugh, 25. "I think it scares a lot of guys, and you're gonna do what you have to do to protect yourselves. But I think sometimes we get carried away."
The U.S. military has re-evaluated its "iron fist" policy in Iraq, but the damage may already have been done.