ISIS overeach

Terror as a weapon of war is capable subjecting many people with few soldiers. Its the ultimate method of Authoritarian conquest, but not so good over the long run.  An example is Islamic State Imposes Strict New Order in Mosul and Deprivation is the Result where the long term prospects of the caliphate's rule based on terror are not good.  That there is no alternative is an advantage that must be chipped away at by the forces of moderation, consumers.