On April 29, Mr. Obama approved an operation to get bin Laden. It was a mission that required surgical accuracy, even more precision than could be delivered by the government's sophisticated Predator drones. To execute it, Mr. Obama tapped a small contingent of one of the Navy's elite SEAL teams and put them under the command of CIA Director Leon Panetta, whose analysts monitored the compound from afar.

The operation was carried out by a 24-man platoon from the Naval Special Warfare Developmental group -- known as DEVGRU -- based out of Dam Neck, Va. It's a group specifically dedicated to high-risk counterterrorism operations and assigned to the Joint Special Ops Command at Ft. Bragg.

A full-scale replica of the compound was erected in the special operations sector of Bagram air base in Afghanistan and the DEVGRU unit practiced assaulting under multiple scenarios -- with many guards, with few guards, with explosives, etc.

"There were multiple opportunities to do that in terms of going through the exercises to prepare for it, so that once they hit the compound, they had already simulated it many times," said Brennan.

The team was operating under the authority of Leon Panetta, the CIA director, since the U.S. military does not have authority to operate in Pakistan. A second team of about two dozen orbited out of sight in case they were needed.

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