Afghanistan ? Insurgents armed with rockets, mortars and a truck bomb staged an unusual frontal attack on a U.S. base in eastern Afghanistan on Saturday, killing two American soldiers and forcing the defenders to call in airstrikes to avoid being overrun.

The assault, which came as thousands of American troops were taking part in an anti-Taliban offensive hundreds of miles away in the south of Afghanistan, pointed up the insurgents’ ability to take the fight to a location of their choosing — in this case a remote outpost in Paktika province, which borders Pakistan’s tribal areas.

The incident also illustrated militant groups’ continuing capability to stage sophisticated, multipronged attacks in Afghanistan’s eastern border zone, despite the Pakistani army’s efforts in recent weeks to rein in insurgents who use the tribal areas in Pakistan as a staging ground.