The first paragraph in an article on the AQ -v- ISIS contest which fits here, my emphais:
The latest edition of Dabiq, the flagship publication of the group that calls itself the Islamic State (IS), includes an eviscerating, accusation-laden polemic against al-Qaeda’s central leadership in Pakistan’s Federally Administered Tribal Areas (FATA). The article, titled, “Al-Qa’ida of Waziristan – A Testimony of Within,” was written by Abu Jarir al-Shamali, an al-Qaeda commander who spent around seven years in an Iranian prison followed by three years in FATA, and defected to IS earlier this year (some media reports that al-Shamali actually spent the immediate post-9/11 years in Iraq rather than Iran)
Link:http://nationalinterest.org/feature/...da-heats-11962