In early 2011, the heart of the Muslim world roiled in protest, consumed with the upheaval of the Arab Spring. The governments of Tunisia and Egypt had already fallen; those of Libya and Yemen would soon follow. Watching the chaos from his hideout in Pakistan, Osama bin Laden saw a historic opportunity: "the next stage," he declared, "will be the reinstating of the rule of the caliphate." Within weeks, bin Laden was dead, shot in the dark...