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Exactly a week before the May 2, 2011 raid that claimed his life, Osama bin Laden authored what may have been his last letter. From inside his Abbottabad safehouse, al-Qaeda's chief had watched as Hosni Mubarak and Zain al-Abedin Ben Ali were overthrown; he was convinced that “the fall of the remaining tyrants in the region was inevitable.” Bin Laden wrote: “If we double our efforts towards guiding, educating and warning Muslim people against half-solutions, by carefully presenting [our] advice, then the next phase will [lead to a triumph] for Islam”. In the year since bin Laden's death, experts have debated whether this is something al-Qaeda can in fact do. Earlier this week, the Combating Terrorism Centre at the West Point military academy in the United States...