Here are some articles to get a handle on the various Islamist militias now operating in Syria. Sarah Birke has an excellent piece in the New York Review of Books explaining the origins of el Nasra and the Islamic State of Iraq and al-Sham.
But ISIS’s real power comes from the fear it seeks and manages to inspire. The group has shown zero tolerance for political dissent. Many Syrians I met along the border mentioned with horror ISIS’s execution of two young boys in Aleppo due to alleged heresy. The kidnappings of local activists and journalists has deterred dissent while also whipping up anti-ISIS sentiment. The group has blown up Shiite shrines, but has also shown few qualms about Sunni civilians getting killed in the process. Beheadings have become common. Father Paolo dall’Oglio, an Italian Jesuit priest who has lived in Syria for thirty years, and who campaigns for inter-religious tolerance, is missing, abducted by ISIS during a visit to the city of Raqqa in late July. As with dozens of others who remain in captivity, ISIS has not demanded ransom or announced his execution; rather it appears to be holding hostages as an insurance against attacks.
This has caused many Syrians to despise ISIS. Since June, there have been anti-ISIS protests in Raqqa—something which requires courage given ISIS’s ruthlessness. More recently, even Islamist activists such as Hadi al-Abdullah, a prominent Syrian from Homs, have criticized the group, describing them as “Dawlet al-Baghdadi,” or Baghdadi’s state, echoing “Suria al-Assad”, Assad’s Syria, the way regime supporters refer to the country. And yet ISIS continues to recruit Syrian fighters. Some say that Syrians joined because the group offers better money and protection than other rebel outfits. In an interview posted to YouTube, Saddam al-Jamal, a former leader of Ahfad al-Rasoul, explains that he defected to ISIS, because moderate fighters are subject to too much foreign interference and are pressured to fight Islamists as well as the regime.
Michael Weiss, in POLITICO, analyzes the rise of the Saudi-backed Islamist front -- an only slightly less extremist Islamist militia than ISIS and al-Nusra.
According to a newly published anatomy of U.S. policymaking in the Wall Street Journal, which cites Obama administration officials, Washington’s objective in arming and training rebels “wasn’t so much to help [them] win as to assuage allies who thought the U.S. wasn’t engaged.” Yet this limited approach failed on two levels: Not only did it destroy the West’s nominal proxy in Syria, but it also compelled Riyadh to “step outside the umbrella” of U.S. oversight altogether and plot the construction of an overshadowing Islamist counterpart army.
Josh Landis has a detailed account of recent fighting and an analysis of the real difference between the militias (which are more strategic than ideological).
Aboud [of the Islamic Front] makes clear that he views ISIS as a potential partner. He is careful to pave the way for its return to the fold. He explains that ISIS’s goal of an Islamic state is not substantially different than that of the Islamic Front or the many other militias fighting in Syria. Where it does differ is that it sees itself as the unique heir to the state and has begun setting up mini-states wherever it rules, pushing aside fellow militias and refusing to submit to the common Sharia court system that the Islamic Front militias and Nusra have constructed and administer together. He points out how Nusra has agreed to cooperate and defer questions of permanent state-building and ultimate governance until after Assad is defeated. This is a way of putting aside what may be fairly substantial ideological differences between militias despite their common goal of an Islamic state and perhaps more importantly, it defers any contest over ultimate executive power. The Emir of ISIS, Abu Bakr al Baghdadi, hopes to assert himself as the Caliph and force the others to give him bay`a or allegiance. He has also imposed rather draconian sharia punishments and forbidden smoking, music, and other simple pleasures that many find intolerable. This underlines the great problems that remain for the militias in determining what form and style an eventual Islamic state will take, not to mention who among the militia leaders will ultimately rule.
Islamic Front leaders have been very skilful about finessing questions on governance. The standard answer they give to those who ask what kind of government they intend is that they will call on an assembly of Ulema to decide on the correct form of Islamic government when the time comes.