In reply to Bootrock:
I guess I can chime in with some specialised knowledge on this considering I've interviewed Syrians, boys who ISIS attempted to recruit, and read testimonies by torturers and ISIS "soldiers".
Assuming that these guys are what you see in the TV shows is a mistake. ISIS prays on young boys and men who are afraid, poor and alone. You can imagine growing up out in the countryside in Syria, with no education beyond middle school, living in a small town with 10-20 houses, nothing to do and your whole life consists of maybe farming, maybe doing odd manual labor jobs. The war begins, and suddenly surviving becomes even harder. Maybe your brothers have to move to Lebanon and Jordan to work and send money back to the family, leaving you all alone. Then some guys roll in with their nice Toyotas, say something about religion, and put a rifle in your hand. Suddenly now, you have power. You can decide your own fate. They tell you to join them in their conquest of the country, where you will get cars, guns, money, women. You know your cousin joined these guys and posts all those cool pictures on FB with guns in his hand and he gets all those likes, people say he's bad ass and God's warrior.
Over time, the religious ideas will harden in that boys head until he believes it himself, because he wants to latch on to something to make himself feel good. He gets told he isn't just a farmer's son growing up in a place no one has heard of, but a chosen man who will spread the word of how people can become like him. People will adore him, and fear him, but he will be a just leader.
And so it goes. It's the same story as every other extremist movement, from 1%ers to religious cults to Nazis. They prey on people who are weak and desperate, and through marketing present themselves as a way out of it.
But the function behind how he became indoctrinated can also be the same function that reverses it in an interrogation. I don't know why people here seem to assume an interrogation is just talking to someone. It's a highly studied field that people train for years to master. It's manipulation of the mind's weaknesses, gaining trust and poking and prodding until the information comes out. And if one guy doesn't crack, then you just need 1 out of 100 to do it and you can take down a whole organisation. Because when you do get the information, it isn't just a small drip to make you stop, you get everything.
With torture, you just fuel the fire. You end up traumatising what is really still just a scared little boy, and you send a message to his friends at home that we really are the devils they make us out to be. It isn't just blustering like your dad said those guys with the cars and guns were doing, it's real. "They're killing us, we have to fight." Not even to speak of the possibility of getting the wrong intel. In short, the downside is huge, but the upside is exactly the same as conventional means.
You don't win an ideological war by force. You win it by talking it to death, by helping those people out in the countrysides so their situations don't get so desperate. Yes it's frustrating and people will die, but at the same time we will starve them by cutting off their resource: Fear, anger and desperation.
I learned a long time ago that when you're in a situation that can spiral into a potential conflict (I worked in a maximum security prison once, and also in the military), it's extremely hard to be mad at a person who is calm and treats you nicely and respectfully.
The only thing you gain by hurting the other person is feeling better about yourself momentarily. But long-term you will lose more than you gain from it.
Post edited at 17:03