Updated

British lawmakers say commanders' complacency and inadequate security were partly to blame for the failure to stop a Taliban attack on a U.S-British base in Afghanistan that killed two U.S. Marines.

The House of Commons Defense Committee said Wednesday that more than half the guard towers were unstaffed at the time of the September 2012 attack on Camp Bastion in Helmand province.

The lawmakers said troops on the base — who at the time included Prince Harry — had been exposed to "unnecessary risk."

In the attack, 15 Taliban insurgents dressed in U.S. military uniforms and armed with rocket-propelled grenades cut through perimeter wire.

In the ensuing firefight, two Marines were killed. Eight American troops, eight British personnel and a civilian contractor were injured.