Most of the soldiers were still asleep when gunfire rang out and insurgents stormed their isolated hilltop base from all sides, killing eight Americans and three Afghan soldiers.
The Americans weren't even supposed to be there. Combat Outpost Keating had been scheduled to be closed months before the Oct. 3 assault. A U.S. military investigation released Friday blamed lapses in oversight and a delay in closing the remote outpost for one of the heaviest American combat losses in a single engagement during the Afghan war.
The findings demonstrate the increasing vulnerability of the Americans and their NATO allies, even as 37,000 U.S. and NATO reinforcements pour into the country. U.S. troops increasingly partner with Afghan forces — often living in joint outposts that are thinly manned and more exposed than larger bases.
The readiness of Afghan forces to take over their own security so foreign troops can leave is a key component of President Barack Obama's war strategy.
The gunbattle broke out when an estimated 300 insurgents — five times the number of defenders — stormed the base with rocket-propelled grenades, mortars and guns just before 6 a.m. in mountainous Nuristan province near the Pakistan border.
Afghan soldiers failed to hold their position on the eastern side of the compound and insurgents penetrated the outpost's perimeter at three locations, according to the report.
The U.S. soldiers "heroically repelled a complex attack" after calling in air support, the report said. When the fighting was over, about 150 insurgents were dead, along with the eight Americans and three Afghan soldiers.
It marked the heaviest U.S. loss of life in a firefight since July 2008, when nine American soldiers were killed in a similar raid on an isolated outpost in Wanat in the same province.
The report recommended administrative actions "to address shortcomings in command oversight" that contributed to the attack and said U.S. Gen. Stanley McChrystal, the top NATO commander, has taken appropriate action regarding Army personnel involved.
The command did not identify those involved or specify any punitive measures, citing privacy laws.
McChrystal also instructed his subordinates to try to prevent similar attacks in the future.
The report did not elaborate other than to say commanders should continuously reassess the need for small and vulnerable combat outposts.
Col. Wayne Shanks, a U.S. military spokesman in Kabul, declined to discuss new measures put in place after the attack because it could reveal force protection measures to the Taliban and their allies.
Many isolated bases have been closed as part of McChrystal's new strategy to redirect forces to focus on more populated areas to protect civilians and blunt the influence of the Taliban.
But Shanks said the military was not abandoning all its outposts.
"With the troop increases that are coming in, we're expanding some and we're building some more," he said.
Combat Outpost Keating, which was surrounded by high ground, was originally established in 2006 as a base for a provincial reconstruction team.
But the soldiers' mission had been reduced to defending themselves, eliminating any tactical or strategic value of holding the ground, the report said.
The base was supposed to be closed in July or August, but that was delayed after equipment and supplies needed to redeploy were diverted to support intense Afghan operations under way in another area.
The report added that the base also was deprived of other intelligence assets that were being used in the ongoing operation in Barg-e-Matal and the search for a missing U.S. soldier in the south.
"The delayed closing of COP Keating is important as it contributed to a mindset of imminent closure that served to impede improvements in force protection," an executive summary of the report said.
"There were inadequate measures taken by the chain of command, resulting in an attractive target for enemy fighters."
Insurgents had staged numerous small attacks that were easily repelled, giving the U.S. force a false sense of security and enabling the militants to study the Americans' tactics as well as the location of weapons systems, barracks and other key infrastructure, the report said.
Militants had launched about 47 attacks during the five months that the Fort Carson, Colo.-based B Troop, 3rd Squadron, 61st Cavalry, had been deployed at the outpost in the Kamdesh district — three times the rate experienced by the previous unit.
The U.S. subsequently withdrew from the outpost and destroyed what remained of the camp on Oct. 6 to prevent enemy use, the report said.
Also Friday, a U.S. service member was killed by a bomb in western Afghanistan, NATO said. The brief statement gave no further details.
In the south, a bomb hidden on a motorcycle struck a crowd watching a dog fight in southern Afghanistan, killing at least three people and wounding more than 30 others, according to police and hospital officials.
The blast on the outskirts of Lashkar Gah, capital of Helmand province, came as U.S. Marines and their NATO and Afghan allies are poised to launch a major offensive against the Taliban in the area.
Dog fighting was forbidden under the Taliban regime but has emerged as a popular pastime in many parts of Afghanistan after the hard-line Islamist movement was ousted in 2001.
Associated Press writer Noor Khan in Kandahar contributed to this report.
© Copyright 2017 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.