Blogging for The New York Review of Books, Malise Ruthven looks long and carefully at the end-times roots of what we variously call ISIS, ISIL, Da'esh, the caliphate or the Islamic State. The most useful addition the article makes to our knowledge is that this movement is very much a strand of mainstream Islamic thought and dogma.
Ruthven alleges young people are particularly drawn to this sort of apocalyptic movement; why that should be so is not explained. I'd surmise it's probably the same escapist urge that drew thousands of young Europeans into the Children's Crusade of 1212. Another set of young candidates for the Darwin Award.
ISIS behavior reminds me of the Reavers in Joss Whedon's Firefly/Serenity oeuvre, employing brutality for its own sake. Or Genghis Khan whose Mongol horde built pyramids of human heads taller than a man on horseback.
