In doing so, they have put themselves further into harm's way, drawing rocket fire from enemies on surrounding mountain peaks and losing at least seven soldiers since February, including their previous commanding officer in a May 5 helicopter crash in bad weather.
With NATO taking charge of security in southern provinces wracked by a Taliban resurgence, the U.S. is increasingly able to focus on stabilizing the dangerous east, extending the Afghan government's authority there and hunting for fugitives like Osama bin Laden.
More than 600 U.S. soldiers have deployed to Naray, a clutch of mud-brick and stone villages inhabited by 30,000 Pashtun tribespeople in Kunar province — a virtually forgotten corner of Afghanistan at the northern end of the belt of eastern provinces patrolled by U.S. forces.
Bin Laden is familiar with Kunar's mountainous terrain from the days of the war against the 1979-89 Soviet occupation of Afghanistan. The province was once a stronghold of Afghan warlord, Gulbuddin Hekmatyar, whose Hezb-e-Islami faction has long held ties with bin Laden and now fights the government of President Hamid Karzai.
American officials say heavily armed remnants of Hekmatyar's group are still active in Kunar and receive aid from militants crossing into Afghanistan from lawless tribal regions in Pakistan. They are also supported by holdouts from the Taliban regime, which was toppled in late 2001 by U.S.-led forces for harboring bin Laden.
But Lt. Col. Michael Howard, commanding officer of Forward Operating Base Naray, said the main challenge facing his American forces is not the virtually impossible task of sealing the frontier from militant incursions but winning the trust of villagers from five local tribes.
"You have a group of people who for years have had one option, and that was to cower to, or be a part of the likes of the Taliban, Hezb-e-Islami or al Qaeda. That was their only choice," said Howard, who runs the 3rd Battalion, 71st Cavalry Regiment of the 10th Mountain Division, based in Fort Drum, N.Y.
"The greatest challenge is making folks realize that things have changed."
Some soldiers in Naray have recently arrived from southern Helmand and Kandahar provinces, where NATO has deployed thousands of forces in recent months — mostly British and Canadian — and last week took over command from the U.S.-led anti-terror coalition. More U.S. soldiers are expected to be shifted to the east in the months ahead.
In recent weeks, U.S. soldiers broke ground further north in Kunar's neighboring province of Nuristan, establishing a tiny outpost and trying to launch road, water and power projects in Kamdesh, an isolated village surrounded by sheer cliffs and often shrouded by low clouds.
Poor weather regularly closes Kamdesh to Chinooks and other U.S. supply helicopters, cutting it off from vital supply routes for several weeks at a time.
On Monday, about 100 U.S. and Afghan forces launched an operation in Nuristan province to destroy a suspected anti-craft gun operated by militants and threatening American helicopters flying between Kamdesh and Naray, said Capt. Dan Walker of the 4th Battalion, 25th Artillery Unit of the 10th Mountain Division. Soldiers were setting up howitzers and mortars, and infantry were preparing to move on foot into mountains to locate the high-powered weapon.
Few foreigners have ventured into this isolated region of Afghanistan. Even in Naray, the only foreigners villagers had previously seen were hashish-smoking Soviet troops, who were based here briefly during the Russian occupation, and U.S.-funded Arab, Chechen and Pakistani mujahedeen who would cross from Pakistan to fight against them.
"The Russians would come knocking on our doors with guns looking for hashish whenever they ran out," said Naray's most prominent tribal elder, white-bearded Rahmat Noor, in his fortified home built on the eastern bank of the roaring Kunar River.
"We all made jihad (holy war) against the Russians because we didn't like them. They were occupiers," Noor said. "But we like the Americans. They came to help. They built a mosque on their base for our soldiers."
Following the Sept. 11 attacks and subsequent hunt for bin Laden, a U.S. Special Forces contingent established a small outpost in Naray. The 10th Mountain Division base has grown around it and has employed more than 1,000 local people.
About 160 Afghan soldiers live side-by-side with U.S. forces at the base, training to use American weapons, like Howitzer cannons.
A medical facility run by the 758th Forward Surgical Team out of Fort Lewis, Wash., and medics from the 3-71 Cavalry's reconnaissance unit have treated dozens of Afghans.
They include a 12-year-old Kamdesh girl, Aleema, whose right foot and bottom half of her shin were blown off by a land mine planted by tribesmen along a tribal border.
"These people first understood that we were here to kill them and the kids would stand off, but now we treat them, give them teddy bears and soccer balls," said cavalry medic Sgt. Michael La Clair, 38, of San Diego. "They know now that we are here to help."