THE SEARCH FOR OSAMA.(Osama bin Laden)

A Q. & A. with Jane Mayer

One day this past March, in Langley, Virginia, there was jubilation on a little-known thoroughfare called Bin Laden Lane. Analysts at the C.I.A.'s Counter-Terrorism Center, a dingy warren of gray metal desks marked by a custom-made street sign, were thrilled to learn that, seven thousand miles away, in Rawalpindi, Pakistan, colleagues from the agency had helped local authorities storm a private villa and capture Khalid Shaikh Mohammed, the man believed to be the third most important figure in the Al Qaeda terrorist organization.

At last, the stalled hunt for Al Qaeda fugitives had gained momentum. The authorities in Pakistan had obtained Mohammed's laptop computer and satellite phone; this breakthrough, they hoped, would help them track down the organization's leader, Osama bin Laden. Analysts in Washington speculated that news of Mohammed's capture might even prompt bin Laden into fleeing his current hideout. According to an F.B.I. official, in the weeks before his arrest Mohammed had been moving from one place to another in Baluchistan, a lawless province that borders Afghanistan and Iran. Bin Laden, it was thought, was probably in the same area.

Days later, American intelligence satellites traced a telephone call made to Baluchistan by Saad bin Laden, one of Osama's sons, who was thought to be hiding in Iran. Intelligence officials knew that bin Laden no longer dared to answer the phone, but they believed the call might have been placed to one of his aides.

An unmanned spy plane dispatched to the region spotted a suspicious convoy moving at night. It consisted of about a hundred people on horseback and on foot, and was advancing along an ancient smugglers' route, in a rocky desert area. Bin Laden, the officials hoped, might be travelling with this group.

A team made up of C.I.A. paramilitary operatives, Delta Force soldiers, and Pakistani officials descended upon the convoy. Meanwhile, in Washington, the C.I.A. had orders to launch a Hellfire missile from an unmanned Predator intelligence aircraft if the presence of bin Laden could be confirmed. After the terrorist attacks of September 11, 2001, President Bush signed a top-secret Memorandum of Notification, calling for bin Laden to be either captured or killed on sight.

"The C.I.A. was very confident--they thought they had him there in Baluchistan, across from the Iranian border," Vincent Cannistraro, a former chief of operations for the C.I.A.'s Counter-Terrorism Center, said. "They had a fixed location on him. They mounted a moderate-sized operation." The convoy was intercepted, Cannistraro said. Each traveller was examined. "Lo and behold, bin Laden wasn't there," he said. The convoy was merely a group of refugees.