Despite some frontline successes and territorial reclamations, the destruction of organizational assets, and the death of thousands of militants, the Islamic State’s ideology of jihad continues its spread from Baghdad to Brussels to Orlando. How can the United States and its allies fight an enemy that is as much idea as it is entity? What securities do ISIS provide recruits that civil societies are failing to? What is ISIS fighting for, how much is it about religion, and how has that changed over time? What parts of this war are bigger than ISIS, and what might we learn for strategic purposes?