Khost, Afghanistan - Less than six hours after a helicopter drops a combined US and Afghan army patrol by the mountain border with Pakistan, Islamic insurgents surround and pound the unit into disarray.
The surprise attack from forested slopes around the troops' positions lasts 20 minutes, during which they are pinned down and barely able to hit back, such is the intensity of the barrage of fire. Then abrupt silence replaces the crash and rattle of rocket-propelled grenades and small arms.
"They know to pull back before air support can arrive," said Sergeant Ryan Hendricks of the 2-506 Infantry Regiment, 101st Airborne Division, as he positions the two dozen soldiers against any attempt to directly storm the hilltop they are holding.