PAKTIA PROVINCE, Afghanistan -- Coalition forces scoured the desolate hills near the border with Pakistan for days and found no traces of al-Qaida and Taliban forces. Nothing in the caves, nothing in the foxholes, nothing in the abandoned observation posts looking out over the valley.
As the war in Afghanistan grinds on, troops are finding it increasingly difficult to find fighters who can launch hit-and-run attacks and melt away into the mountains.
"It's frustrating," said 23-year-old Jon Turner, a British marine laying under the shade on a hilltop with his fingers on a machine-gun and his face painted with dark camouflage colors. "They could be hidden anywhere, there are lots of places to hide."
The latest coalition setback came Sunday, when a U.S. Special Forces soldier was killed by attackers believed to be linked to al-Qaida and the deposed Taliban militia in a mountainous area called Shkin in the east, said U.S. military spokesman Maj. Bryan Hilferty.
Sgt. Gene Arden Vance Jr., 38, of Morgantown, W.Va., was in the 19th Special Forces Unit of the West Virginia National Guard, said spokesman Maj. Mike Cadle.
An Afghan soldier fighting alongside Vance was wounded in the firefight, which also left an attacker dead.
At the main allied air base at Bagram, American flags were lowered to half-staff Monday.
"One casualty does not deter us," Hilferty said. "It certainly makes us realize and understand mortality more, but we're determined to see this mission out to the end. The United States, and I think civilization, is at war against terrorism. So we realize there are risks."
The latest operation was launched Friday, one day after Australian special forces said they came under fire about 12 miles north of the volatile eastern city of Khost.
The Australians were pursued for several hours by men with rocket-launchers and assault rifles before an American AC-130 gunship was called in, killing 10 of the attackers along a ridge-line. Their bodies were not found, and there were believed to be many more who fled. The 1,000-strong coalition force, including four 120-man fighting companies of Britain's best soldiers, was deployed by helicopter to scour the rocky hills. Six 105 mm artillery positions were set up on a hillside nearby to provide covering fire, along with nine 81 mm mortars and four machine gun nests.
On an opposite hill, British troops approached the suspected hide-outs from two sides, slowly searching everything they could in a 4-square-mile area.
"Our troops have found caves, but there is nothing to suggest that there was any enemy stronghold here or any recent enemy activity," said Maj. Richard King, commander of X-ray company.
There was no abandoned food or clothing, few of the defenses set up in past battles. An indentation about 2 feet deep and 3 feet across was carved into the stony ground -- a shallow foxhole for gunmen. On the opposite hill, a man-made structure could be seen that soldiers said was an observation post.
British troops detained one man in a nearby village and flew him to Bagram, but King said there was little reason to believe he had any link to the terrorist network. It was unclear if he was still in custody.
King said the operation would last another day or two.
The last major battles with al-Qaida and Taliban fighters took place in March in the Shah-e-Kot valley. Since then, they've dispersed into small groups and tried to blend with local populations. Others have fled across the border to Pakistan.
Tracking them down is not easy. Nor is identifying their enemy.
Sur Gul, security chief of Khost, said the American attack on Thursday was mistaken. He said a U.S. plane killed nine members of two tribes who were skirmishing. Another press report said the victims were wedding guests whose celebratory gunshots into the air were misinterpreted. A U.S. military spokesman has denied both accounts.
American troops, too, have carried out their own missions that returned empty-handed.
Last week, about 130 soldiers from the Army's 101st Airborne Division swept through hills around Khost searching for those behind a series of rocket attacks on U.S. forces.
Even as that hunt was on, two more rockets were fired toward U.S. soldiers from the other side of town, but the Americans did not find the attackers.
"Counterinsurgency operations are long and slow," King said. "And winning the hearts and minds of men is not something that happens quickly."
In other developments, U.S. Special Forces raided two houses along the porous border that separates Afghanistan and Pakistan, according to local Pakistani officials in the rugged tribal belt. Weapons were found and three men were arrested, said the officials who spoke on condition of anonymity.
In southern Afghanistan, eight U.S. Special Forces soldiers and about 60 Afghan troops raided the Sperwan village home of Kandahar's former Taliban police chief, Hafez Abdul Majid, an Afghan military source said. Majid, who has been in hiding since the Taliban's fall in December, was not found, but his secretary was arrested, the source said on condition of anonymity.