The so-called "Islamic State" (IS) that has swept into power in parts of Syria and Iraq presents an imminent danger to the global community with its capacity as an effective, ideologically motivated, and bloodthirsty fighting force, coupled with its expanding territorial reach, on the ground and online. The IS has taken on a quasi-state form that mixes modernity with ancient rites, and aggressively promotes sectarian violence and religious extremism with a decidedly apocalyptic bent. Too, it has introduced to the Middle East a new level of extremism and brutality, marked by volatile fluidity,...