This volume tells the story of how Al Qaeda grew in the West. In forensic and compelling detail, Jytte Klausen traces how Islamist revolutionaries exiled in Europe and North America in the 1990s helped create and control one of the world's most impactful terrorist movements - and how, after the near-obliteration of the organization during the aftermath of the 9/11 attacks, they helped build it again. She shows how the diffusion of Islamist terrorism to Europe and North America has been driven, not by local grievances of Western Muslims, but by the strategic priorities of the international Salafi-jihadist revolutionary movement.