If there is a positive side to the rise of ISIS, it is that the West has had its head jerked from the sand and has been made to witness a bottomless, bloodthirsty evil: crucifixions, beheadings, enslavement of women, live burial of children, mass executions. But as one analyst writes, this violence is not “whimsical, crazed fanaticism, but a very deliberate, considered strategy” – one that seems to derive in part from a book called The Management of Savagery. In the spring of 2004 a strategist who called himself Abu Bakr Naji published online The Management of Savagery: The Most...