How did Osama bin Laden escape the dragnet that closed in around his mountain hideout in Afghanistan in December 2001?

It's long been a topic of discussion in intelligence circles and among those (myself included) who witnessed the intense U.S. aerial bombardment of Tora Bora that went on for nearly two weeks. Many analysts have suggested that bin Laden slipped through mountain passes into Pakistan, just a few miles away. But assessments of Guantanamo Bay detainees suggest he went in another direction, evading the mujahideen of the Northern Alliance, as well as the small detachments of U.S. special forces who we first saw in the area around December 8th.

The detainee assessments were made public by Wikileaks this week and published by the Washington Post, the Guardian and other media outlets.

One of them, compiled in 2007, is about a detainee called Harun Shirzad al-Afghani. Al-Afghani was a commander in the militant group Hezb-e-Islami Gulbuddin, a close ally at the time of al Qaeda. Al-Afghani claims that the al Qaeda leader escaped the area thanks to a Pakistani militant and cleric called Maulawi Nur Muhammad. And he says bin Laden headed north toward Jalalabad and later to the remote province of Kunar in north-east Afghanistan....