The attackers were driven back in a pitched, four-hour battle, and they appeared to suffer scores of dead and wounded of their own, but the toll they inflicted was sobering. The base and a nearby observation post were held by just 45 American troops and 25 Afghan soldiers, two senior allied officials said Monday, asking for anonymity while an investigation was under way.
With 9 Americans dead and at least 15 wounded , that means that one in five of the U.S. defenders was killed and nearly half the remainder were wounded. Four Afghan soldiers also were wounded.American and Afghan forces started building the makeshift base just last week, and its defenses were not fully in place, one of the senior allied officials said. In some places, troops were using their vehicles as barriers against insurgents. The militants apparently detected the vulnerability and moved quickly to exploit it in a predawn assault in which they attacked from two directions, U.S. officials said.
It was the first time insurgents had partly breached any of the three dozen outposts that U.S. and Afghan forces operate jointly across the country, according to a Western official who insisted on anonymity in providing details of the operation.
The attack underscored the vulnerability of U.S. forces in Afghanistan, which are increasingly stretched thin as they are dispatched to far-flung outposts with their Afghan allies. The United States now has about 32,000 troops in Afghanistan, about one-fifth the number in Iraq, even though Afghanistan is about 50 percent larger than Iraq.
American commanders and NATO military officials said the assault had also reflected boldness among insurgents who had benefited from new bases in neighboring Pakistan.
It underscored the deteriorating situation in Afghanistan, where war casualties have jumped this year and where U.S. commanders have said repeatedly that their force is undermanned.
The fact that the base, on the western side of Kunar Province, was manned by just 70 soldiers was first reported Monday by The Los Angeles Times. The death toll amounted to the worst single loss for the U.S. military in Afghanistan since June 2005 and one of the worst since the Taliban and their Qaeda associates were routed in late 2001.
American and Afghan soldiers inside the base were hit by flying fragments from bullets, grenades and mortars that insurgents fired from houses, shops and a mosque in a village within a few hundred meters of the base, several officials said. At the lightly fortified observation post nearby, American soldiers came under heavy fire from militants streaming through farmland under the cover of darkness. Most of the American casualties took place there, a senior U.S. military official said.
U.S. warplanes, attack helicopters and long-range artillery were urgently summoned to help repel the militants.
But the insurgents made it so far that a few of their corpses were found inside the base's earthen barriers, and others were lying around it, Tamim Nuristani, a former governor in the region, said after talking to officials in the district.
The attack was unusually bold. Taliban guerrillas and other militants in Afghanistan rarely attack better-armed allied forces head on, preferring suicide bombs and hit-and-run ambushes against foot patrols and convoys. But they have made occasional attempts to overrun lightly manned or otherwise vulnerable outposts.
The United States and Afghanistan have been establishing dozens of military outposts, often in remote areas controlled by the Taliban or their allies.
"We're looking at places to stop the flow of insurgents and establish relations with the local tribes," a senior U.S. military official said.
Insurgents have been present in the area for months, including Pakistani militant groups like Lashkar-e-Taiba, a group that was originally formed to fight in Kashmir, Nuristani said.
He said some local people might have joined the militants since a group of civilians were killed in U.S. airstrikes on July 4 in the same area.
"This made the people angry," he said. "It was the same area; the airstrikes happened maybe one kilometer away from the base."
Nuristani strongly criticized those airstrikes, saying that 22 civilians had been killed. The provincial police chief later confirmed that at least 17 civilians had been killed. The U.S. military said planes had struck vehicles of insurgents but has announced an investigation. Days after his comments, Nuristani was removed from his post.
He said that the security in the region was precarious and that insurgents had freedom of movement from the border with Pakistan through 95 kilometers, or 60 miles, of Nuristan Province to the base at Wanat.
For their part, NATO officials gave little further detail of the attack on Monday. "It has been quiet overnight; the insurgents had been pushed away," said Captain Mike Finney, a spokesman for the NATO force in Kabul.
Eric Schmitt reported from Washington, and Abdul Waheed Wafa contributed reporting from Kabul.
