In late 2004, this reporter observed a similar 12-man squad deal with the deaths of two comrades in such an attack. Without rest for six months, and some still wounded from the bombing, they raided home after home along the Euphrates, meeting stares and silence as they sought the hidden killers of their friends.

"It's the unseen enemy. ... It's very frustrating," one said.

"Why won't he come out and fight?" asked another as the squad chafed under their sergeant's discipline and his demands they treat Iraqis whose homes they were searching with respect.

"... Iraqis, they're so ... ungrateful," one young Marine said, peppering his speech with expletives. "I ... hate them."

Another man snapped: "He killed my best friend," he yelled. "It's not fair. I'm not playing this game any more." The Marine opened fire. Everyone froze. The dog that was his target lived.

No one died that day. The bonding of men at war is vital to any army and Marines place great stress on it. But their commander General Michael Hagee was recently in Iraq to remind them to keep emotions in check as Iraq continues to test the limits of the U.S. military.

"We use lethal force only when justified," Hagee said.

"This is the American way of war."