ISIS is building child army force, and let the child executed their captives. I guess if ISIS has destroyed, then that boys will continue their precursors to 'struggle'. Sustainable radicalism.
It is very hard to brainwash the adults, with the fanatic ISIS propaganda. That is why they are targeting the kids. Little children can be easily brainwashed, and in a year or two, they can be converted to highly effective killing machines which don't have humane emotions. Trust me, these children will make the current ISIS guys look like angels in comparison, when they grow up.