'Didn't need to happen': Pentagon seeks answers for deadly Kabul attack

How did the bomber make it through Taliban checkpoints? The Pentagon has sought answers to the deadly attack that killed 13 US soldiers and several Afghans on Thursday. "This didn't need to happen," a US military official said.

By Wednesday night, US intelligence agencies were near certain that an attack was imminent outside Kabul airport, triggering a State Department warning to American citizens to leave the area immediately. Just over 12 hours later, a suicide bomber walked through the large crowds to a gate manned by US troops and detonated explosives, killing at least 13 US service members and several Afghans.