This whole regime thrives on conflict. The caliphate can really only exist while it is attracting followers and gaining territories, and nothing drives followers to a radical cause like mass persecution and the impending threat of outside force. The people living in captured territories don't support the cause, the people living in regions threatened by ISIS don't support the cause, and recruitment for ISIS is tied directly to the feelings of religious persecution and disrespect. If we want to combat ISIS the only way to do it is to create an alternative to the caliphate that is tolerant of religious beliefs and respectful of differences, because the only selling point of radical Islam to the billion odd practicing Muslims worldwide is that it respects and values the way of life that they would personally choose, while the Western world still looks at Islam with suspicion and even aggression. We've created the rock and the hard place, where the options are either religious persecution and disrespect or radical orthodoxy and religious commitment above personal well being. This movement can't grow without Western policies pushing people to make a choice, which means that the only effective way to combat ISIS is to attack their recruitment online, and create policies to harbor a mentality of respect and support for the displaced Muslim immigrants in our communities, and maybe even support an alternative interpretation of Sharia law that is less intent on hacking its way through limbs towards world domination.