Before U.S. forces arrived here in the mountains of eastern Afghanistan, the instruments of war were rudimentary things: mud-brick outposts and aging Kalashnikovs. The American invasion brought with it a shiny arsenal of 21st-century technology, including advanced helicopters to navigate the treacherous landscape.

But as the U.S. military drawdown continues, the sky is emptying of the foreign aircraft that have kept remote outposts stocked with food, water and weaponry. Afghan troops are being handed the outposts, but not the sleek helicopters that have soared overhead, delivering supplies.

Afghans searching for a substitute have found an ancient solution: the plodding, dutiful animals that have navigated these high and frigid mountain passes for centuries.

“Donkeys are the Afghan helicopter,” said Col. Abdul Nasseeri, an Afghan battalion commander here in Konar province.

Already, hundreds of donkeys are sustaining the bases that Americans built, fought to defend and, eventually, left. The shift underscores the vast gulf separating U.S. and Afghan forces, and the inevitable technological regression that will occur once American troops leave.

The hopeful take of U.S. officials is that this is the kind of “Afghan sustainable” approach that, though not ideal, will endure even as Western funding tapers off. But Afghan leaders aren’t happy. After a decade of joint operations and exposure to cutting-edge technology, they want their military to look like the American one they have seen up close. U.S. officials say that is impractical and financially un­realistic.

The United States has spent more than $50 billion on Afghan security forces in the past decade, carrying one of the world’s poorest armies into modernity. The money bought new vehicles and guns for the Afghan army.

But now, as U.S. troops leave the war against insurgents to Afghan soldiers and police, American officials are deciding which bases and resources will be handed over to Afghanistan’s security forces, and which will be destroyed or shipped back to the United States. It’s a contentious issue that Afghan commanders and their U.S. advisers discuss every day.

Afghans want night-vision goggles, which Americans have refused to buy. They want more heavy weaponry and equipment to detect explosives. American commanders say those requests are too costly and not essential to the mission.

More than anything, Afghan soldiers want helicopters. As of now, they have 31, a far cry from the vast fleet maintained by the U.S. forces. Without any assurance that the Americans will give them more, a frustrated President Hamid Karzai threatened to acquire aircraft from non-NATO countries.

With the U.S. choppers on their way out, the donkey trade has risen steadily. The animals, many of which have been redirected from farm labor to military duty, transport everything that soldiers need, from rice to ammunition.

Last week, when U.S. troops visited a mountain outpost manned by Afghan soldiers, they saw two Afghan teenagers leading four donkeys. Each animal carried 10 gallons of water. The key fighting position, the Americans learned, was sustained exclusively by donkey.

“You are the richest and most powerful country in the world. Of course you can afford helicopters. The best we can do is donkeys,” said 16-year-old Qamuddin, one of the donkey handlers. Like many Afghans, he uses only one name. “Without donkeys, there would be no Afghan army.”

Unpaid donkey contracts

But even a solution as seemingly simple and sustainable as donkey supply convoys has become subject to corruption and incompetence, an emblem of the logistical problems plaguing the Afghan army. Just as Afghans are preparing to inherit dozens of bases, all of which will require donkeys for daily or weekly rations, the funding to pay donkey contractors has disappeared. The Afghan army’s relatively modern bureaucracy has proven incapable of acquiring even ancient tools.

Some contractors, mostly local farmers, haven’t been paid for more than a year. In the volatile Pech Valley, where many key strategic outposts have for years been supplied by U.S. aircraft, Qamuddin said he has been waiting nine months for payment. He’s thinking about quitting.

“We need more water!” Afghan Col. Ashraf yelled when Qamuddin arrived at the outpost with his donkeys last week.

“Well, then I need a new contract!” Qamuddin replied.

For their part, U.S. advisers have devoted much of their time to solving the problem of the unpaid donkey contractors — an unexpected puzzle for military leaders typically focused on the machinations of modern warfare.

“Who knew that the end of this war would boil down to donkey contracts?” said Lt. Col. Brandon Newton, commander of Task Force Lethal Warrior in Konar. “I wasn’t trained for this.”

Some American military advisers acknowledge the irony of being deployed to one of the most dangerous parts of Afghanistan only to negotiate donkey contracts. But the “Donkey Problem,” as it has become known in some U.S. military circles, has prompted much ire and urgency because a failure to solve it could result in a paralysis of operations at key outposts.

“If you lose the outposts, the Taliban have an open door to walk right in,” said Sgt. Travis Washington, part of the U.S. military advisory team in Konar.

Systemic problem

On some bases in the province, U.S. commanders have donated prepared meals to their Afghan counterparts so they can be sold and the proceeds used to pay donkey contractors. Others have allowed Afghans to open small stores on bases and use the profits to pay contractors.

But the systemic problem remains largely unaddressed: Somewhere between the Afghan Ministry of Defense and far-flung platoons, funding allocated for resupplying bases has vanished. Donkeys aren’t the only part of the operation affected. Fuel, spare parts and weapons often don’t make it to the troops.

A report released this month by the special inspector general for Afghanistan reconstruction highlighted the scale of the problem.

“The Afghan government will likely be incapable of fully sustaining ANSF [Afghan National Security Forces] facilities after the transition in 2014 and the expected decrease in U.S. and coalition support,” the report said. It cited “deficient budgeting, procurement, and supply systems.”

Across Konar, donkey contractors say they are on the verge of abandoning their ties with the Afghan military.

“I suspect my money has come through, but a commander, soldier or senior officer is using it for his own business,” said Ghiasuddin, a donkey owner in the province. Four of his donkeys have been killed on resupply missions — two by insurgent shellings and two after falling down a rock face.

Ironically, the last American military unit with a permanent team of donkeys was based in Fort Carson, Colo., where Newton’s battalion is stationed. But it was retired in 1956, even before the unit’s senior officers were born.

“I wish I had the donkeys to give them, but I don’t,” Newton said. “This is something they’re going to have to get right.”