Cut the money source.
If they don't have money, they can't grow strong.
Thats a very hard thing to do, as they have anonymous donators, along with that, they always get way through, by asking for ransom from the government.
Dude the only places you see asking to donate to them scumbags are scambags trying to scam, not Isis these guys take country's and then run them in a cruel way yes but they do run them. They are in the middle east taking oil fields an i have seen somewhere making 3 million a day just from oil do you really think donators make a difference? Not sure you have seen one kidnap asking for ransom you have only seen kidnap =head off no money involved because they have enough until people stop buying oil which they obviously will not so them are the same people with blood on their hand black and red blood..