BAAJ, Iraq — When the gunfire broke out, Capt. Sean K. Keneally scrambled over to Master Sgt. Anthony Davis, who was lying flat on his back, and dragged him to a nearby building.
It was too late. Davis, a member of a small team of American military advisers embedded with an Iraqi army battalion in this remote town, was dead. Minutes later, Keneally learned that a soldier in that battalion, with whom the advisers had lived and worked for months, had killed him.
The shock set in, and so did the new reality. "The force that is providing us the security," Keneally said, "is one of the main threats."
The slayings of Davis and a Marine, Capt. Warren A. Frank, in November were not the only times Iraqis in uniform had attacked American soldiers. Military officials have counted seven such deaths in northern Iraq in the last six months, including two soldiers killed on Saturday at a combat outpost south of Mosul.
But this episode has particular resonance because Davis and his team were the heart of the changing American military mission in Iraq. With most soldiers leaving by August 2010, those remaining will be working primarily as advisers to the Iraqi forces, and their security will be ever more reliant on something as intangible as trust.
"American advisory teams are going to be spread more widely and spread more thinly across Iraq, and so the teams are going to be at higher risk," said John A. Nagl, a retired lieutenant colonel who trained such teams and is now president of the Center for a New American Security, a Washington policy organization.
Military transition teams, which have been embedding with Iraqi forces since 2004, are just one type of the small advisory units that have become a major ingredient of counterinsurgency strategy in Iraq and Afghanistan. There are currently 182 such teams in Iraq, accounting for slightly more than 2,000 people mentoring and supporting Iraqi forces like the police and the border patrol.
Brig. Gen. Keith C. Walker, the commander of the Iraqi Assistance Group, which oversees the transition teams, said that the shift to an advisory mission for American forces would mean changes to the way these teams worked, and that they would be integrated more fully into the rest of the military presence.
But he acknowledged that there was only so much that could be done to prevent such attacks.
"There are always fringe elements or rogue elements that are there, and that risk is always present," he said. "But as transition teams build relationships with their Iraqi comrades, I would just argue that the risk and uncertainty goes down. I wouldn't say it's gone."