In the course of the Syrian Civil War, two major rebel factions have emerged who share al-Qaeda's ideology: Jabhat al-Nusra (JN), which was founded at the beginning of 2012 by Abu Mohammed al-Jowlani, and the Islamic State of Iraq and ash-Sham (ISIS). In April 2013, Abu Bakr al-Baghdadi, the leader of the Islamic State of Iraq (ISI—the umbrella front for al-Qaeda in Iraq), proposed that JN and ISI merge together. He thus announced the formation of a new Islamist polity, ISIS, which included territories in Iraq and Syria (ash-Sham). Baghdadi argued that Jabhat al-Nusra had been initially set-up with financial support and manpower from the ISI and therefore that the Syria-focused JN was a mere “extension” of the Iraq-based organization. Jowlani, however, rejected Baghdadi’s proposal to combine their efforts on the grounds that he was not consulted. Subsequently, he renewed JN’s bay’ah (pledge of allegiance) to Ayman al-Zawahiri, the leader of al-Qaeda Central.
In June of 2013, al-Jazeera revealed a leaked letter in which Zawahiri ruled in favor of maintaining a separation between ISI and JN in Iraq and Syria respectively. The network released video footage of Zawahiri reading the letter aloud in November 2013. Many observers interpreted this televised pronouncement from al-Qaeda Central’s leader as a renewal of the call to disband ISIS, although sources within ISIS circles inform me that the video in question had, in fact, been in private circulation among their members for months. In any event, Baghdadi has personally rejected the call to disband ISIS. Similarly, ISIS’s new official spokesman Abu Mohammed al-Adnani, a Syrian veteran of the Iraq War, has also rejected the proposal in even more forceful terms, going so far as to accuse Jowlani of “defection” and affirming that ISIS would not accept geographical limitations based on “Sykes-Picot.”
http://www.currenttrends.org/research/detail/the-dawn-of-the-islamic-state-of-iraq-and-ash-sham