Instead of fighting or starting a war, you can make deals with terrorists. For instance, ISIS can have their own land and they stop the violence and terrorism is return... Like how obama made contracts with iran instead of fighting!
Ah but if ISIS legally ruled a legitimate state it certainly wouldn't last long ISIS are extreme religious lunatics and that doesn't work in a just society, and if a society as brutal and dehumanising as from what I have so far, wouldn't have any citizens they would all be fleeing to the infidel west. Then it all starts again. If someone was running at you with a axe would extend the hand of friendship.