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This year, 22 service members in the U.S.-led coalition have been killed by men in Afghan uniform, which the military calls "green on blue" attacks.
A burst of gunfire snapped First Sgt. Joseph Hissong awake. Then came another, and another, all with the familiar three-round bursts of a U.S. assault rifle -- and the unfamiliar sound of its rounds being fired in his direction.
The shooters were close. His first thought: "Are Taliban inside the wire?"
But it was not the Taliban. Over the next 52 minutes, as his company of paratroopers braved bullets and rocket-propelled grenades in the predawn darkness to retake one of their own guard towers in southern Afghanistan, they found themselves facing what has become a more pernicious threat: the Afghan soldiers who live and fight alongside the Americans.
The attack on Sergeant Hissong's company, on March 1 at Combat Outpost Sangesar, left two Americans dead along with two Afghan assailants. But it was not the first time that Afghan soldiers had attacked forces from the U.S.-led coalition, nor would it be the last of what the military calls "green on blue" attacks. Already this year, 22 coalition service members have been killed by men in Afghan uniform, compared with 35 for all of last year, according to coalition officials.
The attacks, and the personal animosity that officials believe has driven most of them, are threatening the joint-training model that is one of the remaining imperatives of the Western mission in Afghanistan. The future of that mission will be a main topic at a NATO summit meeting this weekend as U.S. and European leaders discuss whether to accelerate their drawdown.
With the coalition as a matter of policy offering only the barest of details about the attacks -- the episode at Sangesar, for instance, was disclosed in a 71-word coalition statement -- interviews conducted during a week at this outpost provided a rare and detailed account of the violence.
At the personal level, the Sangesar attack was a nightmarish betrayal for the units involved, and in the moments after the violence ended, their commanders were already struggling to figure out how the Afghan and U.S. troops who share the base could possibly cooperate again.
They knew how quickly the situation could spiral downward. Just days before, hundreds of U.S. advisers had been pulled from Afghan government offices in Kabul after two U.S. officers were killed by an Interior Ministry employee, worsening an already poisonous atmosphere during the rioting that broke out after U.S. military personnel burned Korans.
The Afghan and U.S. officers at Sangesar, in the opium poppy belt of southern Afghanistan, decided that pulling back from one another was not an option at the base. Instead, they immediately put their men to work together repairing damage from the attack. The Americans also quickly turned down an Afghan Army offer to swap out the Afghan unit based at Sangesar.
Sergeant Hissong's unit had assumed formal command of the outpost on the night of the attack. New to the area, the Americans reasoned they needed the local knowledge of the Afghan unit, which had been in place for some time. The base is in the Zhare district of Kandahar Province, the closest thing to home turf for the Taliban, a group founded at an Islamic seminary a few kilometers from the outpost.
U.S. and Afghan soldiers were back out on joint patrols within a week. Security measures imposed immediately after the attack -- like posting armed guards at the U.S. mess hall -- had fallen away by the end of the month.
In April, U.S. and Afghan soldiers paired up to successfully push the Taliban from a nearby village.
After watching Afghan soldiers kick down doors and clear mud- brick farm compounds, "it's hard not to like some of those guys," said First Lt. Nicholas Olivero, 24, of Fairfax, Virginia. "But I'd be lying if I said there was trust across the board."
Another U.S. soldier added: "I don't always need to have them walking in front of me now. I did for a while."
Yet Afghan soldiers still complain of being kept at a distance by the Americans, figuratively and literally. The Americans, for instance, have put up towering concrete barriers to separate their small, plywood command center from the outpost's Afghan encampment.
Also still in place is a rule imposed by the Afghan Army after the attack requiring most of its soldiers to lock up their weapons when on base. The Afghan commanding officer keeps the keys.
One U.S. soldier nonetheless advised a visitor to take an armed escort to the Afghan side of the base "just in case."
The effort at Sangesar to move past the attack, and the difficulties in doing so, exemplifies the broader struggle that U.S.- led forces face as they seek to accelerate the training of the Afghan Army and police forces to take over before NATO's combat mission ends in 2014.
Sangesar, like hundreds of other coalition outposts scattered across Afghanistan, is split between U.S. and Afghan forces and in a remote and often hostile area.
Its structures are made of little more than sandbags, heavy-duty tents, plywood huts and Hesco protective barriers, hulking bales of canvas wrapped in wire mesh and filled with dirt. The guard towers at Sangesar are essentially wooden frames filled out with sandbags and placed atop the base's exterior wall of double-stacked Hescos.
Specialist Payton Jones, 19, was alone in one of the guard towers around 3 a.m. on March 1 when two Afghans sneaked up. They killed him with a bullet to the head. Within minutes, Staff Sgt. Jordan Bear, 25, who was among the first soldiers on the scene, had been fatally wounded in a volley of fire from the tower. When Sergeant Hissong, a 35-year-old on his third tour in Afghanistan, arrived moments later, bullets were still smacking into the ground near where Sergeant Bear had fallen.
The two Afghans in the tower -- a soldier and a civilian teacher - - were in an easily defended position. The only approach was up a funnel-shaped stretch of open turf that gave them a clear field of fire to repulse any counterattack.
Along with assault rifles, the Afghans had a U.S. machine gun and their own rocket-propelled grenades. One RPG obliterated a sandbagged bunker between a pair of mortar pits at the center of the base, just moments after a U.S. officer had dashed out of it.
Despite the gun and RPG fire, Sergeant Hissong and another soldier managed to sneak closer to the tower along a row of protective barriers. But they could not take a clear shot at the tower's narrow entrance -- its only opening -- without dangerously exposing themselves.
They turned to their grenade launchers but were too close to the tower for the grenades to detonate once fired. Most landed with nothing more than a thud. The ones that did explode hit the tower's exterior, inflicting little damage.
Helicopter gunships were soon overhead but could not risk firing their missiles or explosive rounds -- the base's fuel tanks were right next to the tower.
The paratroopers on the ground tried approaching the tower in an armored vehicle. But it was disabled with an RPG before it could be positioned to fire its powerful gun.
That left Sergeant Hissong and his comrade. After firing 17 grenades, they were down to their last one. They tried to position themselves so they could get a clear shot into the tower -- and enough distance so it would detonate.
Instead, it bounced off a wall and exploded atop a thick fuel line, sparking a fire that quickly shot toward the main fuel supply: a rubber bladder as big as a swimming pool that was now separated from the flames by only a row of protective barriers.
Racing to disconnect the line from the main fuel supply, Sergeant Hissong did not realize that his unit had finally caught a break: Flames were also climbing the wooden stairs to the tower, filling it with smoke.
The Afghans in the tower pushed out an exterior window, jumped about two stories to the ground and ran. They did not cover much ground before being cut down by an Apache helicopter.
The fight was over. But as the Americans and Afghans at the base began to regroup, they soon learned a third conspirator, an Afghan sergeant, remained among their ranks.
At the outset of the attack, the Afghan sergeant had gone to the outpost's entrance and shot the two guards -- a fellow Afghan soldier and an American. Then he sneaked back to his bunk to wait out the fighting with the other Afghan soldiers. His undoing: He had not killed either man at the entrance. The American was hit in the chest plate of his body armor, knocked down and badly bruised, but nothing more. The Afghan guard was shot clean through the shoulder, a serious but not life-threatening wound, and he quickly identified the third conspirator. Afghan forces detained him immediately.
The coalition and the Afghan Army would now have a rare opportunity to interrogate an Afghan soldier who had turned on coalition forces; most are quickly killed in ensuing firefights. Why had three men attacked U.S. soldiers they barely knew? Was it a personal grudge against Americans? Or had they turned to the Taliban?
The detainee has since presumably been asked those questions. But in a reflection of the official reticence regarding green-on-blue attacks, his answers remain shrouded in secrecy. It is not even clear whose custody he is in.