Tense, final minutes of bin Laden pursuit

Half an hour had passed on the ground, but the American commandos raiding Osama bin Laden's Pakistani hideaway had yet to find their long-sought target.

Two of bin Laden's protectors were dead, shot by Navy SEALs, and one of the U.S. helicopters sat crippled in the courtyard. Pakistan's military, kept in the dark about the operation, was scrambling to respond to reports of explosions and gunfire.

The commandos swept methodically through the one-acre compound's main building, making their way to the upper floors where they expected to find bin Laden.

Finally, shortly before 2 a.m. in Pakistan, the commandos burst into an upstairs room. Inside, an armed bin Laden took cover behind one of his wives, said John Brennan, the Obama administration's chief counterterrorism adviser. With a burst of gunfire, one of the longest and costliest manhunts in modern history had ended.

The operation, planned for months but hidden from all but a tiny circle of administration officials, marked the culmination of a search often seemingly so futile that top U.S. intelligence officials would answer questions about bin Laden's whereabouts with a helpless shrug.

The search employed Predator drones, sophisticated signal interception equipment, networks of informants and teams of analysts who scrutinized every video and audio recording from the al-Qaida leader for clues.

In the end, "he was more or less hiding in plain sight," a senior U.S. intelligence official said.

U.S. spy agencies had narrowed the search over the past year by homing in on a relatively mundane target — a small network of couriers believed to be bin Laden's only point of contact to the outside world.

One courier in particular led them to a newly built residence north of Islamabad. "We were shocked by what we saw," a senior administration official said.

The compound's main building was three stories tall but had few windows facing outside. The facility appeared to be worth at least $1 million but had no telephone or Internet connections. Its 12- to 18-foot security walls were topped by barbed wire.

It was far from the tribal areas where lower-level militants dodge Predator strikes. Indeed, it was a short distance from Pakistan's military academy.

Much about the U.S. operation remains shrouded in secrecy. But U.S. officials provided new details on the chronology of events leading up to the raid.

A crucial break appears to have come on May 2, 2005, when Pakistani special forces arrested a senior al-Qaida operative known as Abu Faraj al-Libi, designated bin Laden's "official messenger" to others within the organization. Al-Libi was turned over to the CIA and held at a "black site" prison where he was subjected to what the Bush administration termed "enhanced interrogation techniques."

Al-Libi and other detainees pointed CIA interrogators to another messenger with close ties to the al-Qaida leader. U.S. officials said they started only with the mystery courier's nom de guerre, and that it took four years to uncover his actual identity, his approximate location in Pakistan and ultimately the compound where bin Laden was found.

Obama was first made aware of the potential breakthrough last September. On March 14, he held the first of five National Security Council meetings in the span of a month devoted to the question of whether and how to target the site.

"We weren't certain in August 2010 that bin Laden was there," the senior U.S. intelligence official said. "Earlier this year, our confidence level grew much higher."

That confidence grew in large part because analysts monitored the compound so closely that they came to know its daily rhythms and the identities of its residents. Analysts concluded the compound was built to hide "someone of significance," and that a third family was living on the floors above the courier and his brother.

It remains unclear when bin Laden first arrived, but officials said it appears the al-Qaida leader rarely — if ever — ventured outside.

Indeed, U.S. officials said the timing of the raid was not driven by worry that bin Laden was about to leave, but by the accumulation of confidence that their intelligence on his location was dead on.

Obama gathered his senior national-security team Thursday for a final review of the operation, according to one member who requested anonymity to speak candidly.

Three options were under consideration: The first was a raid using Special Forces, but Obama also was asked to consider a strike from a "standoff platform," most likely a drone. The third — to wait for more definitive intelligence — would have sounded distressingly familiar to a prior generation of officials who had to explain why there had been such reluctance to pursue bin Laden before the Sept. 11 attacks.

It wasn't until 8 a.m. Friday that Obama, in a meeting with national-security adviser Thomas Donilon, his deputy Denis McDonough, chief of staff William Daley, and Brennan, told the group to move ahead.

The president then boarded Marine One for the first leg of a trip to tornado-ravaged Alabama.

The Navy SEAL commandos picked for the mission had trained for weeks, practicing daily at such a precise replica of the compound that they came to know every wall and external feature, as well as where every occupant was likely to be found. Rehearsals also covered a range of scenarios, including the possibility that bin Laden would try to surrender.

In the end, he showed no interest in being captured.

The SEAL team flew from Afghanistan into Abbottabad aboard two Black Hawk helicopters, U.S. officials said.

The most serious stumble occurred at the start: One of the helicopters had a mechanical failure and tumbled into a courtyard, its tail clipping a 12-foot wall. Navy SEALs who were supposed to be dropped safely outside the perimeter were scrambling for cover in bin Laden's yard.

A third helicopter, a Chinook, was dispatched for emergency support. Meanwhile, the team dropped outside the compound joined the unit from the damaged helicopter and pressed ahead, exchanging fire with the courier and his brother until both were dead.

The commandos moved into the interior of the building and reached bin Laden's upstairs living quarters after nearly 40 minutes on the ground. What words, if any, were exchanged with the terrorist are not publicly known, but the SEALs used the code word "Geronimo" to inform commanders they had found the target.

"The woman presumed to be his wife ... was shielding bin Laden," Brennan said. She was "in the line of fire," he added, and was killed, along with one of bin Laden's adult sons. Others suggested the woman killed was not married to bin Laden.

The al-Qaida leader was shot at least once in the head and died instantly, U.S. officials said.

News footage from inside the compound showed the aftermath of a ferocious struggle, with blood-soaked carpets and overturned furniture. A senior U.S. intelligence official confirmed the SEAL team seized material that was being scrubbed for possible leads to other terrorist suspects. All told, four men and one woman lay dead. Only the corpse of bin Laden was carried away.

Only after slipping out of Pakistani airspace did Obama call Pakistan's president, Asif Ali Zardari, to inform him of the raid.