Well, the core of the ISIS fighters AFAIK are still from ChechnyaThat's not what the deserters say. You should really watch that one on ARTE (I'd guess it is still on +7 if not aired again), it should be available in Switzerland. It's shocking on so many levels, and the kill-bride-with-blunt-knife-for-makeup thing isn't the most shocking one.
They say (and I don't think they have a reason to lie) that the "bosses" are mostly Syrians and the cannon fodder are mostly north Africans. The so-called "Europeans" are mostly returning, not going to the front.
I don't see any reason to doubt any of the other atrocities that they describe, which frankly makes the crimes of the Third Reich seem like almost no big deal. As in, the supervisor just cuts your throat if he feels like it. Or, you get wounded in the front line and they leave you to perish, dog will clean up the remains. For some of these, they even have footage, like where they throw people in that hole just as in the "300" movie.
If you listen to the interviews carefully (in particular the guy who runs his own little secret service), you will see that even assuming the armed conflict ends tomorrow, there will be no peace any time soon. What do you think they are hoarding this massive pile of video footage for? What do you think he talks about when he says "we can identify them"? They are already preparing for a massive vendetta after the war. As soon as it's over, they'll arrest anyone who is on any of those videos, and it will be a 3-minute trial with a death sentence.
Boots on the ground in Syria, and a quick ending to ISIS is what is needed nowUnluckily, these two are antipodal to each other. Boots on ground will mean a decade of fighting and people dying for nothing. This is not winnable.
Dropping two or three MOABs would be "quick ending", but for some obvious reasons this is not done. It's something that would definitively work, though (and no, I am not saying "just kill everybody in the country", it is a very different thing to "just kill everyone" and to demonstrate that you are serious about it and that civilians will not serve as shield).
Doing pest control in the banlieues would help. Having a working legal system that actually punishes serious criminals (rather than the average citizen) and a police that isn't a mere bad joke would help. Expelling, not talking about it, aliens who have a criminal record would help (Before someone will almost inevitably call me xenophobic for that statement, note that I am all for foreigners who follow the law and who aren't trying to kill me -- they are most welcome. It's the criminals I want out, nothing else).
In other places, if you attack people in public, police will yell "on your knees" and then they'll shoot to kill. Try and say "I have a bomb" at a station or airport in the USA, and see what happens. Try and say "Hahaha, you will crawl in the dirt, anyone who does not obey, we will kill" in a public interview in China. I'd be very interested about the outcome.
In Europe, they'll just say "Oh well, that is freedom of speech. Come on my friend, why don't you have some extra money". That doesn't work.
Arresting the salafist warmongers and hate preachers as well as the well-known violent radicals would help. We have somewhat over 400 people in Germany who are known to be ultra-radicals, trained in terror camps, and ready to kill people. That's not all, it's just the ones about whom the agencies are 100% certain. We're not talking about innocent people, or possibly innocent. Just the 400+ who are 100% certain to be vicious, dangerous aggressors. The Belgians have more like 5,000 of these (which obviously makes the problem a bit tougher), and nearly all live in one particular suburb (go figure why).
We have a dozen very well-known hate preachers (the guy who trains little girls to stab police with knives among them) who do what they do in open public without any fear of repercussions or consequences. They openly laugh at us and at our stupidity, knowing that nothing will happen. There's people in the middle of London who openly state in interviews that they aim to decapitate people, and they laugh.
What we are getting is really well-deserved. You have to realize that "religious freedom" cannot apply when someone says that he will decapitate people, nor "freedom of speech". You have to realize that "need proof before arrest" is the wrong approach when people are willing to kill hundreds with bombs without remorse. Those are all nice ideas, and they are the principles I would like to live by in my utopian world, but you cannot apply them to people who just give a fuck about your ideas or your values, and to whom your life is worth as much as the dirt under their shoes.
Oh, and when it comes to IS bombers, please try to abstain from saying "but they are Belgians", this is a perverse sophistry -- the fact that someone who was never willing to integrate and who by all means wants to destroy the state has acquired a nationality by some means is no justification to say "but they are Belgians". On paper, yes. But they never wanted to be (or should have been able to get that nationality).