KANDAHAR, Afghanistan -- Sauntering past disguised as shepherds, hostile Afghan forces have been boldly testing Marine defenses at the allied air base in southern Afghanistan.
Concealed by scarves and robes, the men tote Kalashnikov rifles in plain view and count heads among the Marines who face them. That's when the Americans brace themselves inside their sandbagged foxholes.
"It's when they start moving in and out that they're staging for an attack," Marine Cpl. Jason Gravem, 23, of San Diego, said Tuesday.
"They act like sheep herders, but these sheep herders carry radios and call stuff in," said Marine Sgt. Ethan Ramsey, 22, of White Plains, Mo.
"The weird part of it is, they can just appear in an instant," Ramsey said. "There's got to be tunnels."
Suspected al-Qaida or Taliban holdouts have already attacked coalition forces at Kandahar airport once during the past week. Gunmen in the arid scrub north of the runway opened fire Thursday as a C-17 screamed into the air carrying 20 detainees bound for Guantanamo, Cuba.
A heavily guarded dirt-wall compound at the base holds more than 300 alleged Taliban and al-Qaida figures bound for a U.S. prison in Cuba for investigation.
U.S. Marine officials have said they believe the two events Thursday -- the departure of the first detainees and the first fire on forces here -- were unrelated. But the U.S. military is taking no chances.
Air Force, Army and Marine service members sent their second batch of detainees off Sunday, closely flanked by Cobra attack helicopters, while U.S. Humvees rigged with 50-caliber machine guns and TOW missiles sped across the runway below.
On Tuesday, debris rained down on the young Marines in their sandbag bunkers as explosives experts destroyed caches of arms newly found on the runway. It was evidence, Marines said, that hostile forces were massing for another try.
Experts used TNT and other explosives to collapse a mud-walled house and a network of tunnels recently found in the area. The house was only about 100 yards from the base perimeter, and a few dozen yards from one of the areas of fire of last week's attack.
Bulldozers leveled other mud ruins in the area on Tuesday. Foot patrols searched under cover of vehicles armed with machine guns.
The U.S. military on Monday had found mortar fuses and rocket-propelled grenades in the house -- arms that weren't there on previous occasions, Marine spokesman Lt. James Jarvis said.
U.S. forces found the stash after seeing seven men carrying Kalashnikovs and rocket-propelled grenades across the parched dirt plain at sunset Monday.