I don't think they're a death cult at all. They currently control and manage millions of people who are not actually fighting but are going through their daily routines...as long as they toe the line. They have a judicial system, a leader...
The goal of re-establishing the caliphate is not apocalyptic at all. The west spent a few hundred years trying to do the same thing during the Crusades in the name of the old imperial boundaries. ISIS sees themselves as establishing a theocratic state, based on the boundaries of the old caliphate, and moving beyond into the new world. But that's something Islam has been slyly preaching, one way or another, since the sixth century. It's what fueled the original caliphate's expansion. Like all empires, they crumbled. So now the goal is nothing less than re-establishing that empire and incorporating Muslims everywhere else as outposts of that empire.
Which, yes, is crazy, and the equivalent of someone saying they're descended from Caesar and they want to reclaim Rome's territory... But, crazy as that is, it's not a death cult.
The sad thing is that so much of ISIS is in response not to our wicked western ways, but to the random borders established in the Mideast after WWI. Those motherfuckers randomly drew a map of the world with roughly the same care and thought as an eight year old child with a severe learning disability and we've been embroiled in the wars that resulted ever since. ISIS wants to do away with these still artificial boundaries (which have barely changed since 1916 when people who had never been to the Mideast drew the borders) and unite Muslims under one flag.
Now, of course, if you aren't on board with them, you're an infidel. And so you must die.
The apocalypse aspect comes in with their parallel (to ours) belief of a second coming. In their case, it's the successor of Mohammad. He will come and rule in peace (after defeating "Rome") for a specific period of time. Then we get a day of judgement very much in line with what the Christians believe (because, in the end, Mohammad was a plagiarizing fool).
So here's the problem I have when ISIS is portrayed as a death cult obsessed with the apocalypse... Really? Because two thirds of America believes in the same thing. Christianity is a death cult obsessed with the apocalypse. I'd be willing to bet, in fact, that fewer members of ISIS, comparatively speaking, subscribe to the belief.
The real problem is that we are the haves, and they are the have nots. So we can sit on our thrones and look down our noses at everybody, but they have to scrape through every day of their lives. Violence and terror are easy solutions when you're the have nots. If I take everything away from you and then build a Burger King on your front lawn while you contemplate strangling your child so you have one less mouth to feed, you're going to also contemplate blowing up my Burger King. Especially if charismatic individuals tell you that it's Burger King today, the world tomorrow. (Something, by the way, leaders have been promising since Gilgamesh.)
Our boots on the ground reaction is all we really know. But it's also terrorism of a different sort so, yes, the potential to recruit and unify is there as well. But I think their gamble is that we're corrupt and weak. I don't think they're trying to start "World War III," as Pope Francis calls this. I think they're banking on the same thing Saladin and the leaders who defended against the last few Crusades are banking on -- we're afraid to fully commit. If one of us does fully commit, then the allies are afraid to do the same and the war on the homefront starts going south as soon as the bodybags come home.
We've seen this over and over. Most recently with the Ukraine. The west -- and I know this sounds weird to say considering we're living the dream of a fascist military-industrial complex -- is a post-war society. We don't actually know how to or are willing to wield the power at our disposal.
What results is something of a stalemate, punctuated by this slow, creeping terror that takes a toll on the civilians but leaves the leaders divided.
If I were to give them the credit that they're not due, I'd say Paris, and all the other terrorist hits (we averaged one a day so far in 2015) is some sort of diversionary tactic. But for what, I can't imagine. A diversionary tactic without any real program to hide.