This fascinating article http://www.theatlantic.com/features/archive/2015/02/what-isis-really-wants/384980/ will tell you more about ISIS than a thousand Barack Hussein Obama speeches will.
Here's a key extract:
'The reality is that the Islamic State is Islamic. Very Islamic. Yes, it has attracted psychopaths and adventure seekers, drawn largely from the disaffected populations of the Middle East and Europe. But the religion preached by its most ardent followers derives from coherent and even learned interpretations of Islam.
Virtually every major decision and law promulgated by the Islamic State adheres to what it calls, in its press and pronouncements, and on its billboards, license plates, stationery, and coins, "the Prophetic methodology," which means following the prophecy and example of Muhammad, in punctilious detail. Muslims can reject the Islamic State; nearly all do. But pretending that it isn't actually a religious, millenarian group, with theology that must be understood to be combatted, has already led the United States to underestimate it and back foolish schemes to counter it.'