On the topic of ISIL specifically, I found this to be a very interesting read:
>Dissent in the Islamic State: 'Hashimi Advice' to Abu Bakr al-Baghdadi
>The Caliphate was announced, and the people appointed you as Caliph and gave allegiance to you and we gave allegiance to you with them. Then we began waging jihad in the east and west, and so the land yielded to us- despite our few numbers- and the hearts of men trembled before our terror- despite our weakness. And we knocked on the doors of Damascus and we approached the outskirts of Baghdad and we shook the peripheries of Arbil and we penetrated the fortresses of Beirut, London and Paris. So what is the matter that the state of affairs has changed, and the sign has reversed, and the one who feared us has become the one attack us, and the one who was fleeing from us, our soldiers now flee from him?! So where is the damage and where is the fault?!