This is the gateway to resources, research, and analysis the Combating Terrorism Center has produced over the last decade about the Islamic State in Iraq and the Levant (ISIL), also referred to as the Islamic State of Iraq and al Sham (ISIS), the Islamic State (IS) or Da`ish, and its predecessors (al-Tawhid wa-al-Jihad, al-Qa`ida in Mesopotamia (AQI), Majlis Shura al-Mujahidin, Hilf al-Muttayibin and the Islamic State of Iraq (ISI)).Probably more answers there than you have questions.
The Group That Calls Itself a State: Understanding the Evolution and Challenges of the Islamic State which is about a year old, but has good insight:
The evolution of the IS through accident and design led to an organization with the ability to carry out a large number of attacks. From November 2011 to May 2014 (before the IS’s advance into Mosul), the IS self-reported over 19,000 military operations in Iraq alone. The large majority of its attacks were concentrated in Sunni-dominated areas in Iraq, while Shi’a-dominated areas saw comparatively less violence over time. In the short-term, this divide suggests the existence of a natural demographic buffer against expansion by the IS. Over the long-term, the efficacy of this buffer depends on intervening events and actions by other states and groups.
Supporting the activities of the IS is a diverse financial portfolio that includes (among other things) oil, donations, and war loot. This diversity provides some insulation against the loss of any individual component. Oil is important to the IS, but certainly not the only source of revenue. This is not to suggest that the group is financially impregnable, but it does mean that a comprehensive strategy that addresses the group’s varied revenue streams is necessary to effectively minimize the IS’s ability to function over the long term. Another area in which the IS has had some measure of success is in its propaganda campaign. This success comes in part because of the fact that the IS’s messages to recruits differs in important respects from that of an organization like AQ. For example, videos put forward by the IS tend to be filled with rank-and-file members whom potential recruits find much more relatable than AQ’s videos full of leadership figures giving speeches. This “relatability,” paired with slick production techniques and military successes on the ground, appeals to a new generation of recruits for the IS.
Finally, key to the long-term trajectory of the IS is its ability to provide satisfactory levels of governance to people living under its control. In the short-term, the IS has had some success at providing social services to locals that the Syrian and Iraqi governments failed to provide. This success has resulted in some boost to its overall appeal. However, there is no lack of shortcomings in the area of the IS’s governance. Barring adaptation by the group and a reduction in pressure applied by third-party actors, these failures will only increase with time. Highlighting these failures, together with the negative aspects of the IS’s governance, may undercut support for the group.