It started with a courier’s name.

Senior White House officials said early Monday that the trail that led to Osama bin Laden began before 9/11, before the terror attacks that brought bin Laden to prominence. The trail warmed up last fall, when it discovered an elaborate compound in Pakistan.

“From the time that we first recognized bin Laden as a threat, the U.S. gathered information on people in bin Laden’s circle, including his personal couriers,” a senior official in the Obama administration said in a background briefing from the White House.

After the terror attacks of Sept. 11, 2001, “detainees gave us information on couriers. One courier in particular had our constant attention. Detainees gave us his nom de guerre, his pseudonym, and also identified this man as one of the few couriers trusted by bin Laden.”

In 2007, the U.S. learned the man’s name.In 2009, “we identified areas in Pakistan where the courier and his brother operated. They were very careful, reinforcing belief we were on the right track.”In August 2010, “we found their home in Abbatabad,” in an isolated area.

“When we saw the compound, we were shocked by what we saw: an extraordinarily unique compound.”The plot of land was roughly eight times larger than the other homes in the area. It was built in 2005 on the outskirts of town, but now some other homes are nearby.

“Physical security is extraordinary: 12 to 16 foot walls, walled areas, restricted access by two security gates.” The residents burn their trash, unlike their neighbors. There are windows facing the road. One part of the compound has its own seven-foot privacy wall.And unusual for a multi-million-dollar home: It has no telephone or Internet service.This home, U.S. intelligence analysts concluded, was “custom built to hide someone of significance.

“Besides the two brothers, the U.S. “soon learned that a third family lived there, whose size and makeup of family we believed to match those we believed would be with bin Laden.

Our best information was that bin Laden was there with his youngest wife.”There was no proof, but everything seemed to fit: the security, the background of the couriers, the design of the compound.”Our analysts looked at this from every angle. No other candidate fit the bill as well as bin Laden did,” an official said.

“The bottom line of our collection and analysis was that we had high confidnece that the compound held a high-value terrorist target. There was a strong probability that it was bin Laden.

“This information was shared “with no other country,” an official said. “Only a very small group of people inside our own government knew of this operation in advance.

The raid

The operation went smoothly except for a mechanical problem