What did U.S. military know before 9/11?

What did U.S. military know before 9/11?: "WASHINGTON - A top-secret military program set up six years ago to probe the Al-Qaida terrorist network is provoking fierce new debate about the Sept. 11, 2001, attacks.

Military intelligence officers and contractors who ran the clandestine mission, named Able Danger, say that more than a year before the attacks, the operation identified four of the plot's 19 hijackers and produced a chart that fingered ringleader Mohamed Atta."