KANDEGAL, Afghanistan - The firefight last month was mostly bluster, but for the Afghan National Army soldiers assigned to an observation post here, the threat was apparently real enough.

After a 20-minute exchange lit up the night, although no known casualties resulted, daylight revealed that the Afghan squad had abandoned its post. The U.S. Army sent its own troops to fill the position, which overlooks a bridge-building project in the Pech River valley, a cauldron of insurgent activity.

The Americans said the performance by their allies, the Afghan National Army (ANA), was not uncommon.

"The ANA has no concept that it's their country and their job to defend it," complained Army Capt. Robert Stanton, the U.S. company commander who ordered his troops to fill the abandoned post. "Some units are good. But most are crap."

Five years after the defeat of the Taliban, the international project to build a multiethnic Afghan National Army moves ahead fitfully. So far, 30,000 troops out of an authorized force of 50,000 have been trained. But the ANA, whose troops fight alongside coalition forces, still cannot stand on its own.

Although American soldiers praise the training and discipline of some ANA units, more often they express exasperation at their allies' underperformance. They say the Afghans frequently exhaust their ammunition in firefights, shirk duties, sell their fuel and supplies on the black market - then come back to their American suppliers, helmets in hand.

"There's not a whole lot we can do about it," Staff Sgt. Clay Groves said after his soldiers reported that the Afghans were smoking hashish at an observation post. "Just stand behind them when they shoot. Or stand where they're aiming - it's probably the safest spot."

The coalition commander overseeing the massive training program acknowledged that creating a conventional army out of a mélange of Afghan militias and irregular forces had proved challenging, but it is still, he said, a "huge success."

"In some cases you have great harmony," said Army Brig. Gen. Douglas A. Pritt, who heads the training operation known as Task Force Phoenix. "In some cases you have discord. That's a natural process in our mind."

The Afghan army's performance is critical to creating a strong central government and a cohesive multicultural nation, something Afghanistan has never really achieved, even when it was governed by a king. Americans say that a strong Afghan army is also essential before international coalition nations can safely draw down their forces, which now number about 40,000.

The coalition also belatedly recognized the need, along with building a national army, for developing a strong national police force to maintain the peace in areas from which the army has expelled enemy insurgents. Initial efforts to train police concentrated on training officers in forensics to solve crimes, when what was needed was more training for a public-order mission.

"In terms of building a police force, it's a pretty new experience for the international community," said Lt. Gen. Karl Eikenberry, the coalition commander. "It's now on the road. But there's been some trial and error to get it started out." The target now is to train 62,000 police by next year.

In training both police officers and soldiers, the international coalition has had to confront profound cultural divisions. The Afghan army will probably never operate the same way as a Western armed force.

While Afghanistan has a long and proud martial history - it successfully resisted British and Soviet occupation forces, and some current soldiers have decades of experience - fighting was typically conducted by militias that declared their allegiance to local warlords or ethnic groups. They funded their efforts by collecting "taxes" at roadblocks or by participating in enterprises such as opium trafficking.

ANA soldiers, whose units are carefully selected to maintain an ethnic balance, are taught that defending the country is the first order, though Afghanistan as a nation is a relatively modern concept, more theoretical than real.

"I think their understanding of what the military is all about is very superficial," said Pritt, the general who heads the training.

Pritt acknowledged great variation in the quality of ANA outfits, usually attributable to the time they have spent together, as well as in the quality of their leaders.

"They have the same equipment, they have the same weapons, they have the same pay, they have the same food," said Pritt, an Oregon National Guardsman who a year ago was leading recovery efforts after Hurricanes Katrina and Rita. "But a dynamic, proactive leader in this environment can make a huge difference."

At the Kabul Military Training Center this month, the latest recruits were going through advanced individual training on a stark, treeless range littered with rusty armor from past wars and the debris of barracks bombed by the Americans when the Taliban was ousted in 2001.

Three years ago, when the ANA's first units were deployed to the field, most of the trainers were foreigners. But the Afghans have now developed their own drill instructors who receive only intermittent supervision from NATO trainers.

In an exercise to teach basic squad-level movements, two groups of Afghan soldiers provided cover for each other as they stormed a nest of "enemy" soldiers, aiming their unloaded Kalashnikovs and firing imaginary bullets with sound effects: "Bam! Bam! Bam, bam, bam!"

"In the past wars, the fight was about religion," said Lt. Aminullah Wardak, a company commander. "But this war is about our nation. For every ethnic group, the fight is the same."

Some Afghan units draw praise.

Army Staff Sgt. Jerry Neal, based in the Pech valley, described the current unit working with his platoon as "very professional - excellent." He said the Afghans immediately dug defensive positions at their new camp, and on their first mission to recover a roadside bomb, they efficiently established security on all sides, without being instructed.

"Every time we go out on a mission, they say: 'How many guys you need?' " Neal said. "I would fight with them any given Sunday, as we say around here."

But other units are less professional. Some Afghans have stopped hot pursuit of the enemy to fulfill their religious obligation to pray. Stanton described one mission in which an Afghan platoon left the Americans in the field because the mission took a day longer than anticipated to complete. In other cases, he said, the Afghans refuse to join a mission unless the Americans supply fuel - and then promptly sell the fuel.

In recent months, the Afghan defense ministry has taken over some support functions the Americans had performed - logistics, payroll and supply. The transition has been erratic, and Afghans in forward units have experienced difficulties getting supplies.

Pritt said some Afghan behavior that the Americans see as corruption - "How could this be?" - was simply normal Afghan survival skills.

"We are very aggressive about monitoring those sorts of things," Pritt said. For instance, the coalition forces have observed Afghan paymasters demanding a "tip" from soldiers who are receiving their cash wages.

"If we weren't there saying, 'No, it's not OK, and don't ever ask that question again,' we know that that corruption would occur," Pritt said. "It's a cascading thing."

But he defends Afghanistan, saying, "It's really not a society of corruption. It's a society of survival - survival of self, survival of family, survival of tribe."

The challenge facing the people fashioning the new Afghan army is to teach a new survival instinct - survival of nation.