It was as if the five years of almost ceaseless firefights and ambushes had been a misunderstanding – a tragic, bloody misunderstanding. More than 40 US soldiers have been killed and scores wounded in helicopter crashes, machinegun attacks and grenade blasts in the Korengal Valley, a jagged sliver 10 kilometres deep and 0.8 kilometre wide.The Afghan death toll has been far higher, making the Korengal some of the bloodiest ground in all Afghanistan, according to US and Afghan officials.In the pre-dawn hours of Wednesday, the American presence here came to an abrupt end. The day before, Captain Mark Moretti, the 28-year-old commander of US forces in the valley, walked two dozen Korengali elders around his base and told them the US was withdrawing.He showed them the battle-scarred US barracks, a bullet-ridden crane, wheezing generators and a rubber bladder brimming with nearly 23,000 litres of fuel.Moretti, the son of a West Point physics professor, sat with Shamshir Khan, a valley elder whose son had been jailed for killing two US soldiers, on a small wall near the helicopter pad. In keeping with custom among friends, they held hands.Moretti gently reminded Khan of the deal they had reached days earlier: if US troops were allowed to leave peacefully, they would not destroy the base, the crane and the fuel.Khan assured him the valley’s fighters would honour the deal.”I hope that when I am gone you will do what is best for your valley and the villagers,” an almost wistful Moretti said.”I want you to travel safely to your home, to your family,” the 86-year-old elder replied. He gazed at the officer through thick glasses that magnified rheumy, brown eyes and beamed.In the previous week, hundreds of US Army Rangers and Afghan commandos had pushed into the valley to control the high ground the enemy would need for a big attack on departing troops. Dozens of cargo helicopters hauled off equipment.By Wednesday morning, the last Americans were gone.For US commanders, the Korengal Valley offers a hard lesson in the limits of American power and goodwill in Afghanistan. US troops arrived in 2005 to flush out al-Qaeda and Taliban fighters. They stayed on the theory that the American presence drew insurgents away from areas where the US had a better chance of fostering development. The troops were, in essence, bullet magnets.This year a new set of commanders concluded the US had blundered into a blood feud with fierce and clannish villagers who wanted, above all, to be left alone. By this logic, subduing the Korengal was not worth the cost in American blood.The retreat carries risks. Insurgents could use the Korengal as a haven to plan attacks in other parts of Afghanistan. The withdrawal could offer proof to other Afghans that US troops can be forced out.The American hope is that pulling out of the Korengal rectifies a mistake and that Moretti’s troops can be put to better use stabilising larger, less violent areas where the US presence is more tolerated and there is a greater desire for development.”You can’t force the local populace to accept you in their valley,” Moretti says. ”You can’t make them want to work with us.”Most of the Korengal’s 4000 to 5000 residents live in stone houses that cling to the valley’s steep walls. To survive they grow wheat and log towering cedars in defiance of a government ban on timber exports. They speak their own language.For most of the past five years US troops have exercised loose control over the first five kilometres of the valley. Beyond that the insurgents have had free rein.When he arrived last June, Moretti sent his troops into villages that had not seen a regular US presence in a year. His plan was to drive the enemy back and persuade the elders to support a US-funded effort to pave the sole road into the valley, a project that had stalled in 2007.The road would connect the Korengal to the rest of eastern Afghanistan and in theory make it more governable.In September, as road construction was to begin, insurgents killed six guards hired by the road contractor and took their weapons. The contractor quit.Moretti’s predecessors had spent countless hours trying to persuade Zalwar Khan, an interlocutor between the Americans and the insurgents, to rally the locals to support the road. Three years of prodding had produced virtually no progress.Moretti sensed that the real power in the valley lay with the men leading the insurgency. He asked Khan to give them a letter.He advised Moretti to write to an insurgent leader known as Nasurallah. ”It is our belief that you are the rightful leader of the Korengalis,” the captain wrote. ”You hold the power not only among the villagers but also among the fighters. If you want the valley to prosper, all you have to do is talk with us and bring your fighters down from the mountains.”The letter offered two choices: development or death. ”It is not our wish to kill your fellow Korengalis,” Moretti said. ”But we are good at it and will continue to do it as long as you fight us.”The response was: ”If you surrender to the law of God then our war against you will end. If you keep fighting for man’s law then we will fight you until Doomsday.”Soon after General Stanley McChrystal took over as the top US and North Atlantic Treaty Organisation commander last year, he flew to the Korengal to meet Moretti. McChrystal was reluctant to put any more troops into the stalemated fight. But he also was hesitant to leave, out of concern that a US defeat in the Korengal would raise questions about US will and embolden other insurgents, US officials said.”Do you think you can turn the valley?” he asked Moretti.”I really believe we can make a difference,” Moretti told him.In the months since, Moretti and his commanders became convinced that the Korengalis’ main ambition was to drive the Americans from the valley. They received training, money and weapons from supporters in Pakistan and the Middle East. But the Korengalis’ fight was local.”I don’t believe there are any hardcore Taliban in the valley,” said Lieutenant-Colonel Brian Pearl, who oversees US military operations in the Korengal and a half dozen other valleys in eastern Afghanistan.Last week McChrystal flew back to the valley. Moretti walked him through the plan to pull out his 154 troops.”Sir, I think we are looking forward to getting out of here,” Moretti said. ”I think leaving is the right thing to do.”Moretti’s troops had learnt from the experience of earlier units how to survive in the valley. They knew which ambush sites to avoid. They also patrolled areas that had not seen a US presence in years in an effort to keep the enemy off balance.In 10 months the unit lost only two soldiers. ”In this place, with all its violent history, that is our proudest achievement,” he said.The Washington Post