The recruiting sergeant.

Where did ISIS come from.
A fighting force in Syria, a successful invader of Iraq, an army that can obtain sophisticated arms and the know-how of how to use them. They put the well armed American trained Iraq army to flight and were at the gates of Baghdad before the American bombers gave the Kurds a chance to turn the tide.
Nation states are in dread of them. The world politique is warning of the dangers of ISIS fighters merging into civil society creating chaos and mayhem throughout the democratic world.
Where did they come from, Ali Baba's Cave, Genies out of a bottle, where were they lurking 15,10,5 years ago.  Under which stone were they hiding ?
Their recruiting comes from a dis-effected section of the Muslim diaspora stretched across the world. Partially integrated into various societies they retain their cohesion through their religion. Its a cohesion that is extremely powerful, in essence more powerful than anything else and potentially a threat to the host nation if the underlying dissatisfaction becomes "a cause". 
The fear of every 'nation state' is a group whose  cohesion is not under the states control. Religion is more powerful than the 'secular state' in that it achieves adherence through the mystique of a promise of a life in paradise after death.
The power of religion has been diminished in societies where science has bred agnosticism through the scientific interpretation of known facts.
Religion sadly doesn't let facts getting in the way if they disagree with the bible, (which ever bible is used) and so the religious person is compensated, which ever way the truth pans out. He/she has nothing to loose.
Tie this strong compulsion to practice the formality of the religious belief in an adherent, with repeated confirmation of the faith through daily prayer and its codification, using pageant and symbolism and its a short journey dependency. Once dependant the movers and shakers in any group have something pliable to work with and the aims of these influential  people can take many forms.
From a prophecy of hate to the prophecy of love, the congregation is a captive audience and we see the recruiting of missionaries and suicide bombers in the same light.