The Korengal Valley in eastern Afghanistan was a transit route and occasional haven for insurgents, so U.S. commanders decided to drive out the enemy and turn the local villagers into allies. That was in 2005. By this week, after five years of intense combat that cost 42 American lives, U.S. troops had fought their way halfway down the steep-sided, heavily forested valley — which is just six miles long.

That's five years and 42 lives for three miles of terrain. On Wednesday, the Pentagon announced that U.S. forces are withdrawing from the Korengal, leaving only a small outpost at the mouth of the valley. The Taliban will probably claim a victory over the "infidel" invaders, but the reality is that nobody "lost" the Korengal. The remote declivity doesn't fit into the Obama administration's new strategy of protecting the civilian population. A decision was made that the Korengal simply isn't worth winning.

This is almost certainly the right call. But I can't help worrying that the Korengal is not just a metaphor but a template for the whole war. When the day inevitably comes when we pack up and leave Afghanistan, what will we have accomplished?

"The Korengal Valley is sort of the Afghanistan of Afghanistan: too remote to conquer, too poor to intimidate, too autonomous to buy off," writes author Sebastian Junger. "The Soviets never made it past the mouth of the valley. ...When the 10th Mountain rolled into the valley in 2006, they may well have been the first military force ever to reach its southern end. They were only there a day."

Junger, author of "The Perfect Storm," made five one-month trips to the Korengal Valley in 2007 and 2008 as an embedded reporter with U.S. troops. Junger's newest book, titled "War," will be out next month. It chronicles the experiences of a platoon of soldiers who fought, and watched their friends die, in the Korengal.

Junger's book offers no grandiose theory of how to combat terrorism. It is a gripping account of how modern warfare is experienced by those who do the fighting, and its focus is that of a laser, not a floodlight. He reaches just one grand conclusion about the nature of war: that in the final analysis, you kill the enemy not because of nationality or ideology, but because if you don't, the enemy might kill you.

"I think from the beginning of human history, squad by squad, skirmish by skirmish, that's all it's ever been about," Junger said Thursday in a telephone interview. "It's an issue of survival. I don't think you find politics on the battlefield."

He meant that you don't find geopolitics in a battle like the one waged for the Korengal Valley. But "War" is full of stories that prove the adage about all politics being local. In one incident, U.S. soldiers not-so-accidentally killed, and subsequently ate, a cow that belonged to a villager. This necessitated a negotiation with tribal elders over compensation — and at stake was whether the locals would help the Americans ambush the Taliban, or vice versa.

I asked Junger about the reaction of the U.S. soldiers he had met in the Korengal to the decision to pull out. "For the guys I was with, it's a pretty painful thing," he said.

I can't help but worry that a larger mistake is being made. President Obama soon will have tripled the number of U.S. troops in Afghanistan. The new strategy of focusing on the populated heartland means withdrawing from remote outposts such as the Korengal, but our allies in Pakistan fear that this makes the border more porous to Taliban and al-Qaida fighters. President Hamid Karzai, our ally in the project of nation-building in Afghanistan, is a leader who bitterly denounces the presence of U.S. and other foreign troops and whose government is universally recognized as corrupt.

How many more will die before we leave the country? And what will we have accomplished?