What does ISIS/ISIL and World War Z have in common?

 So in Max Brooks’ book World War Z, which bears nothing in common with movie beyond the title and zombies in general, he posits an enemy that does not behave by any of the accepted rules.  In most modern warfare, there is a premise that after a certain amount of attrition, the enemy ceases to be a threat.  We can degrade an enemies, Command and Control or Logistics support and they will stop being belligerent.  Maybe more importantly, the enemy can be scared into giving up. In World War Z, the enemy doesn’t behave like this.  The zombies have no Command and Control.  They have no logistics lines.  They are each individual fighting forces that need to be killed in order for them to stop being a threat.  The US Military takes a while to figure this out and suffers some horrific loses along the way.  I wonder if ISIS/ISIL is not similar to the Zombie threat from World War Z.  They claim to be a nation state, a caliphate, but they are not in the traditional sense.  The US is attacking them like a nation state, but they are not retreating.  They are not collapsing.  It is as if they don’t realize they are out gunned.  Maybe it is that they don’t care.  Each individual ISIS/ISIL member doesn’t need direct Command and Control to know what to do.  They don’t need Logistic lines to do what they need to do.  They are not scared of the US and its allies.  DO we need to treat ISIS/ISIL like the zombies in World War Z?  Do we need to kill them to the last man?  Many may argue the answer is “Yes”, but I would contend that is not the US’ way.  The stated goal is to defeat them, not to wipe them from the face of the earth.  So if they do not react the anticipated way a Nation State should react to the threat the US and its allies pose, how do we defeat them?  Is ISIS/ISIL is really nothing more than an overgrow terrorist network and threat, then they need to be dealt with accordingly.  Now the $1,000,000 question is what is that?  As it can be argued we have failed to effectively deal with a large terrorist threat for the last 13 years.  I think that I can confidently say a few things.  First, until the local population wants them out, there is little that the US can do.  Sure we need to ensure that those opposed to ISIS/ISIL have the means to resist.  Having been in that part of the world more than once, getting the arms needed to defeat ISIS/ISIL are readily available to the local population.  If the US introduces more arms into the region, much of them will end up in ISIS/ISIL’s hands as they already have.  Second, fighting a conventional war with a proxy force will not work.  It didn’t work in Viet Nam, Afghanistan, or Iraq.  There is no reason to believe that enough has changed for it to work now.  Third, the more legitimacy that we give ISIS/ISIL by calling them a Nation State or a direct, credible threat to the US, the more strength we give them.  Marginalizing them on the world stage is the only way to weaken them in the eyes of their supporters.  Remember in World War Z, the zombies were once part of our supportive, loyal population, but a virus infected them and they turned on us.  Why is the ISIS/ISISL situation different?