ISIS originated as a Sunni jihadist insurgent group during the U.S. invasion of Iraq, and for the past decade it has been the country's pre-eminent extremist group. During that time it has operated under various names, including al Qaeda in Iraq and the Islamic State of Iraq. The group was notorious for its indiscriminate use of violence, which partly explains why it lost much of its popularity. Coupled with the death of its leader Abu Musab al-Zarqawi, this decline in popularity marginalized the group for the next several years. The complete withdrawal of U.S. and allied forces at the end of 2011 enabled the group, then helmed by Abu Bakr al-Baghdadi, to recover. Since then, violence attributed to the group has increased and has remained steady across Iraq.
The group has survived and sometimes thrived in security vacuums. In fact, many of its attacks were meant to incite chaos, which could reignite Iraq's sectarian civil war. Thus the Syrian civil war was a natural fit for the group, which sees the conflict as a broader manifestation of the ongoing struggle in Iraq. Wars produce and attract extremists, and ISIS, the moniker the group adopted after expanding into Syria, could easily absorb both foreign and domestic fighters. For their part, Syria's rebel groups needed experienced fighters with knowledge and weapons in their struggle against the al Assad regime. Meanwhile, non-combatants did not really care about who was in charge so long as they could obtain basic necessities, such as food, water and shelter, and security — nor did they have the ability to resist them. This enables groups like ISIS to take control of territory, and al-Baghdadi moved quickly to exploit that ambivalence.
ISIS tries to maintain a centralized command structure as much as is practical or feasible. Given that its operations span at least two countries — and given the local conditions of the conflict — the actual battlefield command structure is diffused.
ISIS units on the battlefield report to emirs, who are the group's designated leaders in a city or province. For example, the takeover of Azaz was instigated on the initiative of the local ISIS emir. Thus ISIS leaders maintain considerable autonomy in their operations across Syria and Iraq. This autonomy is apparent when some ISIS emirs collaborate heavily with local rebel forces while others try to secure areas much more independently and much more aggressively.
However, al Baghdadi still maintains ultimate command of the group. ISIS emirs may conduct localized operations on their own initiative, but the propaganda and ideological direction of the conflict appears to remain heavily centralized. In the few cases where ISIS units have been seen to deviate from the edicts of the core of ISIS, leadership has not hesitated to banish the groups, as evidenced with the Mujahideen of the Caucasus in the Sham.
Its Own Worst Enemy
Whether centrally or locally directed, ISIS aggression has steadily expanded into multiple fronts against multiple actors. The group is waging an insurgency in Iraq, and it is also battling against the al Assad regime, Kurdish forces and secular, Western-backed rebel groups in Syria. It has even broken from the al Qaeda core.
Notably, on Sept. 24, 11 of the Syrian rebellion's most prominent brigades issued a joint statement under the moniker of the Islamist Alliance. This alliance included moderate Islamist groups as well as hardline ones. ISIS was excluded. This does not necessarily mean that these groups have outright rejected ISIS, but it does demonstrate that even other hard-line rebel groups understand ISIS's extremism and are willing to politically distance themselves from it.
If ISIS attempts to fight the Turkish army along the border, it will incur heavy losses. However, the border is long and difficult to control. Turkey has closed some key border crossings, which are located near some important ISIS strongholds in northern Syria, but there are many smuggling routes between the two countries to which Ankara turns a blind eye (it wants to keep some rebel supply lines open). ISIS therefore has considerable access to Syria and could stage attacks in Turkey's borderlands relatively easily. It is unclear whether ISIS will have the equipment and expertise necessary to conduct such attacks effectively, but the group could certainly stage limited operations, even in Istanbul and Ankara, that would have at least some political effect.
But Ankara has long had to contend with militants, in this case the Kurdistan Workers' Party, and there is also some built-up capacity to deal with terrorist attacks in the country. The car bombing in Reyhanli is an excellent example. The attackers, who were probably sponsored by the Syrian regime, meant to strike deep inside the city but were forced to execute early due to security measures that would have exposed them. ISIS would have to dedicate significant resources to be effective in the Turkish borderlands, and even more would have to be dedicated for the group to have a chance at threatening the interior.
Pursuing this multi-front war will overextend ISIS's capabilities and add to the already building animosity toward the group. It could also reverse what gains the group has made in Syria, as happened with al Qaeda in Iraq in 2006. Indeed, the group's bravado has played into al Assad's hands; its involvement in the conflict has severely tempered Western backing of the rebellion. In many ways, ISIS is its own worst enemy.