KABUL/WASHINGTON: The rout of Afghan forces as Taliban fighters take one provincial city after another provides a stark answer to anyone wondering about the success of two decades of US-led efforts to build a local army.

Despite about $89 billion budgeted for training the Afghan army, it took the Taliban little more than a month to brush it aside. Over the last few days, the insurgents have seized every major city in Afghanistan - from Kandahar in the south to Mazar-i-Sharif in the north, Herat in the west to Jalalabad in the east.

They now stand at the gates of Kabul.

Afghan President Ashraf Ghani praised Afghan security and defense forces in a brief televised address on Saturday, saying they had "a strong spirit to defend their people and country."

But still, there has been shock at the lack of resistance put up by many Afghan army units. Some abandoned their posts and others reached agreements with the Taliban to stop fighting and hand over their weapons and equipment.

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In some instances, US officials say, provincial governors asked security forces to surrender or escape, perhaps in order to avoid further bloodshed because they believed defeat was unavoidable.

Where deals were not cut, Afghan forces still appear to have melted away.

"Once morale goes, it spreads very quickly, and that is at least partly to blame," a US official said.

American officers have long worried that rampant corruption, well documented in parts of Afghanistan's military and political leadership, would undermine the resolve of badly paid, ill-fed and erratically supplied front-line soldiers - some of whom have been left for months or even years on end in isolated outposts, where they could be picked off by the Taliban.

Over many years, hundreds of Afghan soldiers were killed each month. But the army fought on, without any of the airborne evacuation of casualties and expert surgical care standard in Western armies, as long as international backing was there. Once that went, their resolve evaporated.

"Would you give your life for leaders who don't pay you on time and are more interested in their own future?" a second US official, speaking on the condition of anonymity, asked.

It is an analysis shared by some in the Taliban movement itself.

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One Taliban commander in the central province of Ghazni said the government forces' collapse started as soon as US forces started withdrawing "as they didn't have any ideology except fleecing the Americans."

"The only reason for this unexpected fall of provinces was our commitment and the withdrawal of US troops," he said.

The defeat highlights the failure of the United States to create a fighting force in the image of its own highly professional military with a motivated, well-trained leadership, high-tech weaponry and seamless logistical support.

On paper, Afghan security forces numbered around 300,000 soldiers. In reality, the numbers were never that high.

Dependent on a small number of elite Special Forces units that were shunted from province to province as more cities fell to the Taliban, the already high rate of desertion in the regular army soared.

As government forces started to fall apart, hastily recruited local militias, loyal to prominent regional leaders such as Marshal Abdul Rashid Dostum in the northern province of Faryab or Ismail Khan in Herat, also rushed in to fight.

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Western countries had long been wary of such militias. Though more in line with the realities of traditional Afghan politics where personal, local or ethnic ties outweigh loyalty to the state, they were also open to corruption and abuse and ultimately proved no more effective than conventional forces.

Dostum fled to Uzbekistan as the Taliban advanced and Khan surrendered to the insurgents.

But whether it was ever a realistic goal to create a Western-style army in one of the world's poorest countries, with a literacy rate of 40% and a social and political culture far from the developed sense of nationhood underpinning the US military, is an open question.

US army trainers who worked with Afghan forces struggled to teach the basic lesson of military organization that supplies, maintaining equipment and ensuring units get proper support are key to battlefield success.

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Jonathan Schroden, an expert at the CNA policy institute, who served as an advisor to US central command CENTCOM and the U.S.-led international force in Afghanistan, said the Afghan army functioned as much as a "jobs program" as a fighting force "because it's the source of a paycheck in a country where paychecks are hard to come by."

But the chronic failure of logistical, hardware and manpower support to many units, meant that "even if they want to fight, they run out of the ability to fight in relatively short order."

Afghan forces have been forced repeatedly to give up after pleas for supplies and reinforcements went unanswered, either because of incompetence or the simple incapacity of the system to deliver.

Even the elite Special Forces units that have borne the brunt of the fighting in recent years have suffered. Last month, at least a dozen commandos were executed by Taliban fighters in the northern province of Faryab after running out of ammunition and being forced to surrender.

Richard Armitage, the former US diplomat who organized a flotilla of South Vietnamese Navy ships to carry some 30,000 refugees out of Saigon before it fell in April 1975, has watched as the threat of a similar disaster unfolds in Kabul.

As deputy Secretary of State under former President George W. Bush when the United States invaded in 2001, he was deeply involved in Afghanistan diplomacy. He said the Afghan army's collapse pointed to the wider failures of two decades of international efforts.

"I hear people expressing frustration in the press that the Afghan army can't fight a long fight," he said. "I can assure you the Afghan army has fought, can fight and if it's got a trigger and something comes out of the barrel, they can use it."

"The question is, is this government worth fighting for?" he said.