Before the U.S. invasion of Iraq, I read a book trying to explain Saddam Hussein's behavior. The conclusion was: the dude is nuts. And crazy people follow a different logic, which we can't predict because it doesn't follow the orthodox logic that the rest of us sane people use. So while we were saying, "The only reason to risk invasion and deposition by not allowing nuclear inspectors to return is because you are violating the nuclear arms restrictions placed upon you," Saddam Hussein was saying, "I'm not going to allow inspectors because purple monkey dishwasher."
I saw a headline today about the "confusing strategy" of Islamic State. Is this another instance of crazy strategy isn't really strategy? I don't think so, because this time we have a group that is very willing to tell us their strategy. It might seem crazy, but it doesn't need to be confusing.
Islamic State reads future history as being about the return of the Mahdi. His return will be presaged by violence and plague killing one-third of the world, so Islamic State is helping hasten the return of the Mahdi by spreading violence. Illogical, but not confusing.
What makes it "confusing" to Western observers is a hesitance to take Islamic State at their word. They say they're an Islamic caliphate. We say, "Well, you can't mean that," because we don't want to besmirch Islam. So when they do something like attack Parisians, and they tell us why, we spend time being confused.