The scariest thing about ISIS is what few seem to understand. Their goal is not to win in any normal sense of the word. Their goal is to precipitate a massive conflict (Armageddon) with the rest of the world that does not share their beliefs (including other Muslim nations) that will cause the return of their God to smite their enemies and establish the whole world as the caliphate.
Their goal is destruction of any kind that will pull the rest of the world into conflict with them. They have no allies. They have no great strategic goals. They will do anything to draw the West into a conflict despite obvious evidence that they cannot win because they truly believe their god will return to win it for them.
In the end - they are all kamikaze warriors who will continue to become more extreme until they achieve their desire. Nothing is off limits for them. They are the enemy of all and all our muddling about in the sandbox has taken our eye off the biggest threat of all.
The answer then is to kill all the ISIS bastards, every pea-picking last one of them.
They’re brain-fried & only extermination will end their murderous spree and might deter the recruitment of more of them.