Two military officers have been relieved of their commands as a result of the litany of mistakes, but neither faced criminal charges, a military official familiar with the investigation told The Associated Press on Wednesday.
A report on the investigation said the platoon leader and company commander — whose names were not released — failed to provide proper supervision to the unit or enforce military standards.
A seven-page summary of the investigation provided to the AP also said it appeared insurgents may have rehearsed the attack two days earlier, and that Iraqi security forces near the soldiers' outpost probably saw and heard the attack and "chose to not become an active participant in the attack on either side."
"This was an event caused by numerous acts of complacency, and a lack of standards at the platoon level," said the investigating officer, Lt. Col. Timothy Daugherty, in the summary.
Three 101st Airborne Division soldiers were killed in the June 16, 2006, attack. Spc. David J. Babineau, of Springfield, Massachusetts, was found dead at the scene, and two others — Pfc. Kristian Menchaca of Houston and Pfc. Thomas Tucker of Madras, Oregon — were abducted. Their mutilated bodies were found three days later, tied together and booby-trapped with bombs.
Details of the attack and what led up to it came as thousands of U.S. and Iraqi forces were scouring the same area near Youssifiyah, in what is called the Triangle of Death, for three soldiers believed to have been abducted Saturday by an al Qaeda-related group.
According to the investigation of last June's attack, Tucker, Menchaca and Babineau were ordered to guard a mobile bridge over a canal in order to prevent insurgents from planting mines. Other members of their platoon, who were at two locations up to three-quarters of a mile away, heard small arms fire at 7:49 p.m. When they arrived at the checkpoint about 25 minutes later, Babineau was dead and the others were gone.
Daugherty said the soldiers had been told to stand guard for up to 36 hours with just one Humvee, and there were no barriers on the road to slow access to them or provide early warning.
To expect them to operate an observation post for 24 to 36 hours was unrealistic, he said. "From the time a vehicle was seen, it would have been in front or beside the (Humvee) in a matter of seconds," he wrote.
Daugherty concluded that the platoon did not get the supervision or direction it needed. And he said the unit was hurt by the loss of 10 troops, including several leaders, who were killed in action as well as by the need to shuffle the platoon's leadership three times.
The platoon also had been dogged by an ongoing investigation into the rape and killing of an Iraqi girl and the killing of her family by several other members of the unit.
Daugherty said there was no malicious intent by the officers who were leading the unit.
"Although the leaders in this platoon care and are staying in the fight, the platoon is frayed," he said in his report.
Daugherty's investigation found no evidence linking the three soldiers' deaths to the rape-murder, which occurred three months earlier. An al Qaeda-linked group, the Mujahedeen Shura Council, claimed in July that the attack on Babineau, Menchaca and Tucker was revenge for the rape-killing.
In other developments: