Abstract: Russia’s recent intervention in Syria will generate more opportunities for the Islamic State than it quells. If the Islamic State’s core defenses around major cities in Iraq and Syria hold, the Islamic State will weather Russia’s intervention and likely emerge stronger. The Islamic State has an effective defensive strategy, which it employed in the summer and early autumn of 2015. Apart from failing to compromise the Islamic State’s defenses, the Russian intervention will fracture the U.S.-led coalition and weaken Syrian rebel groups, giving the Islamic State freedom of action on fronts where it had been constrained previously. Committed opponents of the Islamic State still have opportunities to block and fix the group’s forces on multiple fronts, but these efforts will fail if a successful ground counter-offensive does not free the Euphrates valley and Mosul from the Islamic State’s control. Russia’s attempts to remove the United States from Iraq and Syria will significantly degrade the formulation of such a ground strategy, and the Islamic State will benefit.
The Islamic State’s defensive strategy within Iraq and Syria is holding. Russia’s intervention in Syria and burgeoning efforts in Iraq may cause the Islamic State to reconsider its next move, but the group’s defense will not be easily compromised, especially as Russian strikes have so far focused primarily on Syrian rebel groups in a 9:1 ratio. The Islamic State only needs to maintain the status quo within Iraq and Syria to succeed. Its claim of being a new caliphate remains intact while it still controls major cities. The Islamic State’s aims are greater, however, and it wants to do much more, if it can weather the current storm. The group’s ultimate goals are to rule all Muslims within an Islamic caliphate and to win an apocalyptic war against the West. The Islamic State’s campaign in Iraq and Syria furthers these goals by allowing it to demonstrate that it can defend its caliphate. The Islamic State prospers even while under fire by broadcasting its ability to endure. The Islamic State also accelerates its expansion under conditions of limited duress, allowing it to counter-balance any losses while also being able to boast of expanding its caliphate. The Islamic State is an adaptive enemy, and its defenses are difficult to break, despite the host of adversaries it currently faces.
The Islamic State’s summer and early autumn 2015 campaign in Iraq and Syria demonstrated that the group can pursue its objectives conservatively, surviving under pressure and holding its own while balancing against its losses. Ultimately, during this campaign the group succeeded in maintaining the status quo within Iraq and Syria. It also used the summer campaign to set conditions to alter the status quo to its advantage in 2016. Before Russia’s intervention, it appeared that the Islamic State might launch an offensive against the Syrian regime south of Homs. As of October 2015, the group is likely reconsidering its next move, given Russia’s apparent commitment to preserve the Assad regime. The Islamic State may maintain its conservative stance, but opportunities are mounting for the group to exploit competition among local and strategic opponents to stoke greater instability even as its own losses accumulate.
Russia’s involvement increases rather than mitigates these opportunities because it is likely to weaken competing rebel groups in Syria in addition to the U.S.-led coalition. The Islamic State launched a major ground offensive against rebels north of Aleppo on October 9 while Russian airstrikes targeted rebels west of Aleppo, taking advantage of the fact that Russia’s barrage is not focused on the group. Russia’s air campaign near Turkish air space has also stalled the U.S.-Turkish partnership to establish a “Free Zone,” reducing rather than enhancing the pressure placed upon the Islamic State from the air. Failure to break the Islamic State’s ground defenses in Iraq and Syria and to block its future exploits will allow the group to emerge stronger in the midst of such opportunities, with a greater claim to endurance and more opportunities to attack. This is an outcome the U.S.-led coalition must prevent in the midst of Russia’s actions. Ceding the anti-Islamic State fight to a Russian-Iranian alliance that is less committed to defeating the group will instead drive Syrian rebels toward al-Qa`ida in Syria, reduce opportunities to find a political settlement in Syria, and increase the Islamic State’s freedom of action.
The Islamic State’s Defense
Defense is the Islamic State’s primary objective within Iraq and Syria, a point made by Alexandre Mello and Michael Knights earlier this year. Defense is not a sign of weakness, but rather an expression of durable control. The group’s control of cities allows it to claim that the caliphate exists. The Islamic State’s grand strategy appears to depend upon sustained control of cities, around which all other strategies, including its global messaging campaign, revolve. In order to propagate a claim to lead the caliphate, the Islamic State must hold its claimed territory against aggressors. Its military defense was most visible in the summer and early autumn of 2015 in Ramadi, Mosul, and Raqqa, though the Islamic State’s defensive lines around Raqqa began to fail in July 2015. The group’s successes are nevertheless noteworthy, because it will be devastating to Iraq and the region if the Islamic State wins the current battle of Ramadi, while no challengers emerge to contest its claim in Mosul.
The Islamic State successfully defended Ramadi over the summer and into the autumn of 2015. The Islamic State’s static defenses in Ramadi likely pale in comparison to the rings of improvised explosive devices (IEDs) and trenches around Mosul, as Ramadi did not fall to the Islamic State until May 18, 2015. The group nevertheless held its ground there under deliberate counter-attack for most of that period. Effective mobile defenses that used ambushes and vehicle-borne IEDs (VBIEDS)a may account for the Islamic State’s success. The Islamic State’s accomplishments in Ramadi may also reflect the use of zone defense, in which it launched main attacks in other locations to divert the attention of the Iraqi Security Forces (ISF). The Islamic State persistently targeted Baiji and the Baiji oil refinery in northern Iraq throughout the summer,[b] making it impossible for the ISF to mass forces at that time in Ramadi. The Islamic State also launched an aggressive campaign against ISF positions east of Fallujah [c] within a few kilometers of Baghdad’s western edge during and after the Islamic State’s successful capture of Ramadi.[d]
The Islamic State also successfully defended Mosul over the summer and early fall against peripheral incursions by the Peshmerga forces from the Kurdish Democratic Party that were supported by coalition airstrikes. These measures did not constitute an existential threat to the Islamic State’s stronghold in Mosul, however. The Islamic State’s untested static defenses around the city are reportedly robust, including trenches, patrols, IED rings, and human shields. The group conducted an area defense in a number of separate campaigns against the Kurdish line, including Sinjar,[e] Mount Bashiqa, Gwer, and Makhmour in order to keep Kurdish ground forces engaged at a short distance from Mosul. The attacks may also have been probing attacks with greater implications for future Islamic State offensives. The group launched a mustard gas attack against Kurdish positions southwest of Irbil in August 2015,[f] shortly before conducting a similar attack along the Syrian Kurdish line,[g] indicating that the Islamic State may either be deterring further Kurdish counter-offensives or that it may be contemplating new offensives against the Kurds in late 2015 and 2016.
The Islamic State’s attacks against the Kurdish line may also have been punitive responses to its failed defense of northern Syria over the summer and early autumn. The group had attempted to close a gap in its line between Raqqa and Aleppo provinces by clearing the Kurdish enclave in Kobane, but this operation failed in late 2014. After blocking the Islamic State’s operation in Kobane, the Syrian Kurdish People’s Protection Units (YPG) exploited this gap and widened the distance between Islamic State-controlled cities in northern Syria. The YPG pushed out from both Kobane and Hasaka provinces to seize the Islamic State’s nearby border outpost at Tel Abyad in June 2015, a major blow to the group. The loss of Tel Abyad cost the Islamic State one of two major border crossings into Turkey. More importantly, it also compromised the Islamic State’s area defenses around Raqqa city. Raqqa city has been one of the group’s strongest urban positions, and one of its most sophisticated experiments in governance. The loss of Raqqa would set the Islamic State back significantly in terms of its claim to govern within its caliphate.
Raqqa also appears to be one of the weakest fronts of the Islamic State’s tested military defenses, and it remains an important opportunity for the U.S.-led coalition. The YPG proceeded from Tel Abyad and Kobane to seize Ayn Issa and Serrin [h] by August 2015, nearby towns that effectively isolated the Islamic State from its other positions in northern Syria. The Islamic State responded with a classic zone defense, attacking Kurdish positions in neighboring Kobane and Hasaka provinces.[i] The Islamic State was at times successful in recapturing towns and villages from the YPG. As of mid-October 2015, however, the Islamic State’s defense of Raqqa is failing, with anti-Islamic State forces reportedly within 45 kilometers of Raqqa city. An indication of Islamic State concern were reports the group was conscripting residents of Raqqa as young as 14 into its ranks.
Instead of reinforcing this front with assets from elsewhere in Syria, the Islamic State appears to be reinforcing other fronts, such as Deir ez Zour, possibly with the idea of clearing regime forces from the city. De-prioritizing the defense of Raqqa may indicate that the Islamic State regards its northern adversaries as formidable; however, Kurdish and Arab ground forces north of Raqqa have a contentious relationship, and the Islamic State may instead be counting on the likelihood that Arab civilians in Raqqa city would reject a predominantly Kurdish liberation force. Losing control of Raqqa city would constitute the group’s greatest loss since its urban campaign began in January 2014. But the Islamic State appears to be considering new offensives despite the potential defeat in Raqqa, and it has set conditions to counter-balance the setback by seizing new territory.
The Islamic State generally held its other positions across Iraq and Syria over the summer and early autumn. The group still boasts strong defenses in northern Aleppo, in the vicinity of Deir ez Zour, in outer Anbar, and in the Zaab triangle north of Hawija. It faced internal resistance in several of these areas, but a coercive approach to maintaining social order appeared to quell opposition in each case. In one instance, citizens of Rutba near the Jordanian border protested the Islamic State’s rule in July 2015. The Islamic State put down the demonstration by detaining more than 200 citizens of Rutba, whom some sources claim were killed. In September the group detained and executed religious leaders and 50 “salafis” in Hawija for refusing to pledge allegiance to the Islamic State. An IED attack against an Islamic State financier south of Mosul on June 23 claimed by the “Mosul Independent Youth,” however, indicates that the Islamic State’s control over its northern strongholds in Iraq has become loose enough that resistors can mobilize isolated attacks. On the whole, the group’s coercive power behind its defensive line did not show signs of decay over the summer and early autumn. With the notable exception of Raqqa, the Islamic State’s defenses held fast.
The Islamic State Attempts to Maintain Status Quo
The loss of an urban center like Raqqa could be devastating for the Islamic State without a deliberate plan to counter-balance the defeat. The group previously demonstrated its resilience in the face of equivalent setbacks, such as losing control of Tikrit in early 2015. The Islamic State responded to the ISF’s counter-attack at Tikrit by targeting Baiji and Ramadi.[j] These efforts were more than diversionary attempts to alleviate pressure on Tikrit; they were separate objectives to gain new cities. Success in capturing one would allow the Islamic State to claim a net neutral outcome if it lost Tikrit, which ultimately occurred in April. The group likely planned offensives over the summer of 2015 with the expectation that it could lose Raqqa, Ramadi, or its free access to the Turkish border through Syria. The Islamic State also had to compensate for the loss of Tikrit and its nearby oil fields, and its summer and early autumn campaign reflects efforts to preserve the integrity of its caliphate despite potential operational failures.
The Islamic State executed two main offensives over the summer of 2015 in Iraq, both likely designed to counter-balance the potential loss of Ramadi. It persistently attacked Baiji[k] and Haditha,[l] both cities that the group ultimately desires to control. Both cities contain critical infrastructure, and both are situated closer to the Islamic State’s strongholds than to those of the Iraqi state. The Islamic State’s attacks there doubled as zone defense for Ramadi, but they are more than diversions. They are targets of the group’s future conquest, which the Islamic State modulates in order to enhance its overall defense. The Islamic State also acts to balance and preserve its access to lucrative resources. The group attacked the Ajil and Alas oil fields east of Tikrit repeatedly over the summer.[m] The Islamic State had controlled them prior to the loss of Tikrit. The Islamic State may ultimately seek to control the northern oil fields in Kirkuk as a grandiose alternative. The Islamic State also attacked the Jezal oil fields[n] north of Palmyra in September. The Islamic State’s access to resources is far from expended, and the group continuously seeks new avenues of sustainment.
The Islamic State’s boldest balancing move came in May when its forces attacked and seized the Syrian city of Palmyra, along with its seizure of Ramadi in Iraq. The move preemptively counter-balanced the potential loss of Raqqa, which Islamic State leaders likely realized had become vulnerable after the failure of the Kobane campaign in late 2014. Palmyra additionally gave the Islamic State access to Homs, Damascus, and the Syrian central corridor, replete with new cities and new access to borders. Palmyra also gave the Islamic State the opportunity to claim to be an anti-regime actor in order to set conditions for future engagement of the Syrian opposition and Jabhat al-Nusra, the Syrian al-Qa`ida affiliate.
The Islamic State is also preparing to consolidate along the Euphrates by expelling the Syrian regime from Deir ez Zour.[o] This has high stakes because Russian air assets in Syria in September 2015 have the potential to strike in eastern Syria. The Islamic State controls the villages and tribal areas around Deir ez Zour city, and it is positioning forces to attack the airbase and remaining neighborhoods in the downtown area that are still under regime control. Deir ez Zour is the Islamic State’s next move to counter-balance further losses in Raqqa province should the YPG assault continue.
The declaration of a U.S.-Turkey partnership in pursuit of a “Free Zone” could also disrupt the status quo, isolating the group from its global network by cutting access to the Turkish border. The fate of the Free Zone has been jeopardized by Russia’s intervention, but the Islamic State undoubtedly made plans to balance any loss of cross-border access. As of October 2015, the Islamic State appears to be penetrating rebel systems in Aleppo, Idlib, and Dera’a in order to gain new access to Turkey and Jordan. The group has attacked rebel positions north of Aleppo near Mare’a multiple times with ground forces and VBIEDS,[p] including an aggressive assault on October 9, and it is likely responsible for a string of assassinations of rebels and Jabhat al-Nusra figures in Idlib[q] and Dera’a.[r] The Islamic State had been attacking Hezbollah on both sides of the Qusayr border with northern Lebanon, though the future course of this penetration may be altered by Russia’s defense of the Assad regime.[s] The Islamic State may additionally seek to open new border access through Iraq to Jordan, Saudi Arabia, or Kuwait. In order to maintain the status quo, the group will pursue these routes in order to outpace measures that block its access to the Turkish border.
The Islamic State has ambitions beyond the status quo. The group likely seeks to claim a former caliphate capital such as Baghdad, in order to assert its legitimacy; to destroy rival militaries in order to preserve its long-term defense; and to leverage Iraq and Syria to destabilize the Middle East in support of broader expansion. Without the Russian intervention, the Islamic State’s attacks west of Palmyra against the T4 Airbase,[t] Homs city,[u] and Qusayr, for example, could very well have set conditions for an offensive by the Islamic State to break the back of the Syrian regime’s military by the end of 2015. Concurrent Syrian rebel offensives against the regime in northern Latakia, Aleppo city,[v] and northern Damascus[w] forced the Syrian regime to pull troops back by early September 2015, and the Islamic State was ready to compound the impact on the regime by attacking south of Homs.
The establishment of a Russian airbase in Latakia on Syria’s coast in September 2015 may stave off the Syrian regime’s precipitous collapse by preventing both Syrian rebels and the Islamic State from advancing along Syria’s central corridor. The Islamic State nevertheless remains able to launch such an attack while it holds Palmyra and surrounding villages, and Russian airstrikes have not concentrated upon protecting the regime against the group’s position there. The Islamic State may still pursue this course, but as of October 2015, it is likely waiting to see what becomes of Russia’s intervention. If it cannot break the regime, and Russia continues to attack Syrian rebels, the Islamic State may attempt a closer alignment with al-Qa`ida and rebels in Syria in order to advance near Damascus more quietly.
Similarly, the Islamic State’s extremely high casualty attacks[x] in Diyala province in Iraq in July–September may draw both the ISF and Iranian-backed militias into a defensive posture along Iran’s border, breaking their defenses in Baiji and west of Baghdad and terminating their current offensives in Ramadi and Fallujah. These shifts will justify more aggressive involvement by the Iranian axis in Diyala, which will constrain the U.S.-led coalition and further inflame regional sectarian tension. The Islamic State may attempt low probability/high impact attacks against Shi’a shrine cities in Iraq to accomplish the same purpose. The Islamic State attempted at least five attacks on Karbala over the summer from Anbar’s western desert.[y] It also repeatedly positioned its forces for attacks into Samarra,[z] causing Shi’a militias and the ISF to launch repeated counter-offensives to clear Islamic State forces from the desert west of the city.[aa]
Offensives by the Islamic State against Syria’s Alawite heartland and Iraq’s Shi’a heartland could be diversionary efforts to support its strategic defenses. But given the degree to which other ground forces in Iraq and Syria are spread thin, it is feasible that the Islamic State could launch low probability/high impact attacks that actually work. Such strikes would be game-changers in the current geopolitical environment if they succeed either in crippling rival militaries or in stoking regional war. Defense within Iraq and Syria may be sufficient to support the Islamic State’s broader goals, but the group is still the most likely actor on the ground in Iraq and Syria to set new terms of battle. Given the opportunity, the Islamic State will seize the initiative, even while Russia proceeds with its new Middle East strategy.
New Constraints and Exogenous Opportunities
The Islamic State’s cross-border access through Aleppo province in Syria has not yet been blocked, and it likely still has sufficient manpower to both defend and launch new operations under current conditions. The Islamic State remains capable of launching new offensives, and it is encouraged to do so as a way to retain the initiative and generate options for its overall defense. Continued separate ground counter-offensives against the group’s positions at Raqqa, Ramadi, and Hawija could alter this balance by fixing the Islamic State in a static defensive posture, a weakness it has not experienced in many years. The U.S.-led coalition is supporting three such efforts as of October 2015: the YPG and Arab rebel groups north of Raqqa; peshmerga from the Popular Union of Kurdistan near Hawija; and the ISF at Ramadi. Such parallel efforts would be greatly enhanced if the Islamic State were also blocked west and south of Palmyra, but neither Russia nor the U.S.-led coalition has done so. The Islamic State’s expansion may therefore proceed despite constraints on multiple sides.
None of these efforts will topple the Islamic State’s military unless operations fully clear their forces from these cities; or alternately shape decisive operations against the group in Deir ez Zour or Mosul. The Islamic State could lose its ability to defend creatively if it is pinned in multiple corners, but its defenses will not crumble while it can still claim interior strongholds. The Islamic State may have regarded the vulnerability of being fixed on multiple fronts as a serious threat in early October 2015, compounded by the potential for Russia and Iran to focus their attacks upon the Islamic State. The Islamic State may have massed forces in Deir ez Zour to consolidate in a static defensive posture in reaction to this threat. But its leaders are likely learning over the course of the Russian air campaign that the group will not be threatened in this way. The Islamic State is therefore beginning to proceed with its signature defenses and preemptive offensives, most notably against Syrian rebels north of Aleppo.
Meanwhile, obstacles to effective coalition ground partner strategies are mounting. Iraq’s political problems are at crisis point. Wide-scale protests across Baghdad and southern Iraq coupled with intra-Shi’a militia competition could generate instability and violence that require Iraq to divert security forces away from the frontline. Concurrent moves by Iranian-backed Shi’a militias to undermine Prime Minister Haider al-Abadi’s political reforms may degrade Baghdad’s security. Kata’ib Hezbollah has already clashed with Federal Police in Baghdad and at Iran’s behest has kidnapped Turkish workers in Baghdad. The creation of a joint Russian-Iranian-Syrian-Iraqi coordination cell in Baghdad will create further opportunities for the Islamic State by limiting the influence and freedom of action of the U.S.-led coalition in Baghdad. The Islamic State may not be in a military position to challenge security forces in Baghdad and southern Iraq on its own, but Iraq’s current political crisis may give the Islamic State opportunities to re-kindle its battle in Baghdad, and in Basra, where the group claimed an explosive attack on October 5.
The Islamic State also seeks opportunities to undermine the U.S.-led coalition against the Islamic State. The Islamic State might have focused its energies upon disrupting the U.S.-Turkey partnership to this end, or to provoke greater sectarian response to the Iran deal. Instead, Russia’s President Vladimir Putin positioned himself as the leader of a new coalition battling the Islamic State,31 putting SU-30 fighter aircraft just south of the Turkish border, and a joint coordination cell in Baghdad, severely undercutting the U.S.-led coalition. It is doubtful that Russia will degrade and defeat the Islamic State from the air more effectively than the United States, though it will certainly inflict greater civilian casualties and drive the Syrian opposition closer to al-Qa`ida in Syria, given that its air campaign is focused upon the Syrian opposition rather than on the Islamic State. If Russia were serious about defeating the Islamic State, it would have focused its air strikes on Palmyra, which would have degraded the group’s defensive flexibility in concert with U.S.-led operations elsewhere. But this is not Russia’s objective. Instead, there is a high risk that Russia will fracture the U.S.-led coalition and stoke regional escalation against the Iranian axis, outcomes that support the Islamic State’s long game in the region. In the long run, Russian intervention will widen the space for anti-Western actors in the Middle East, strengthen the Iranian axis, and polarize the region in ways that the Islamic State will continue to exploit.
Overcoming the Islamic State’s defenses remains the basic task necessary to be completed in order to create the conditions needed to expel Islamic State forces from all cities. The Islamic State will not be defeated while it can claim control of cities in Iraq, Syria, and elsewhere in the region. The campaign to defeat the Islamic State has to outpace the group’s efforts to generate redundancy and momentum, because they give the Islamic State a means to counter-balance otherwise meaningful gains by their opponents. Developing a ground strategy takes time, but the Islamic State benefits from more time. Fixing the Islamic State in multiple corners of its caliphate could have halted its expansion and limited its defensive options, creating new operational opportunities for the opposing coalition in the coming year. But Russia’s intervention has likely blocked the U.S.-led coalition from maximizing this opportunity. Furthermore, the fundamental challenges of retaking interior cities and tribal areas such as Deir ez Zour and Mosul without ground partners positioned nearby remain. The Islamic State’s defenses will therefore likely hold well into 2016 unless the U.S.-led coalition regains the initiative in Iraq and Syria quickly.
Meanwhile, the Islamic State will ensure its interior defenses are not compromised because of its pre-positioning throughout the region. The group now controls cities and towns elsewhere in the world, specifically in Sirte, Libya and in Afghanistan, where it claimed to control seven district centers as of late September 2015. The more the Islamic State can generate depth outside of Iraq and Syria, the less powerful a centralized geographic campaign to defeat the Islamic State within Iraq and Syria will be. Meanwhile, the Islamic State is scaling its measures to provide for defense, maintain the status quo, and expand to support its global campaign. The Islamic State has already counter-balanced significant losses in Iraq and Syria by opening new fronts, including Egypt, Saudi Arabia, Yemen, and the Caucasus. 
The strategy to defeat the Islamic State must therefore have hounds as well as hunters, arrayed regionally to prevent it from evading defeat by reaching farther out. The United States is still the global power with the greatest potential to develop such a broad coalition strategy. The Islamic State’s global campaign runs the risk of out-pacing coalition efforts, however, resulting in an array of caliphate satellites that the Islamic State could begin to incorporate into a transcontinental military campaign. The longer the group can endure, and the more places in which it is present, the harder it will be to defeat. The Islamic State will therefore remain and likely expand in 2016.
Jessica Lewis McFate is the Research Director at the Institute for the Study of War. She is a West Point graduate (‘04), and she served on active duty in the United States Army as an intelligence officer with multiple deployments to Iraq and Afghanistan. She has published extensively on the Islamic State of Iraq and al-Sham (ISIS), including “Al Qaeda in Iraq Resurgent,” “The Islamic State: A Counter-Strategy for a Counter-State,” and “The ISIS Defense in Iraq and Syria: Countering an Adaptive Enemy.”
[a] The Islamic State detonated a suicide, vehicle-borne IED (SVBIED) north of Ramadi on August 27, 2015, killing the Iraqi Army 10th Division commander and the Deputy Commander of the Anbar operations. “Iraq Conflict: Bomb kills two generals near Ramadi,” BBC, August 27, 2015; “Two Senior Officers Killed in a Suicide Explosion in Al-Anbar,” Radio Sawa, August 27, 2015.
[b] The Islamic State attacked Baiji with vigor in May 2015, seizing large parts of the city and claiming to control the Baiji oil refinery. The ISF and Shi’a militias pushed the Islamic State out of the city in June 2015, but the city has been contested since. For more information, see the Iraq Situation Update series at the Institute for the Study of War.
[c] The Islamic State’s attacks east of Fallujah were likely more than the Islamic State required in order to defend Fallujah itself, a city which it has held firmly for 20 months. For more information on how the Islamic State seized Fallujah in January 2014, see Jessica D. Lewis, “Iraq Update 2014 #1: Showdown in Anbar,” Institute for the Study of War, January 3, 2013.
[d] The Islamic State attacked positions ranging from Garma, Camp Mazraa, and Amiriyat at Fallujah before and during its final assault on Ramadi on May 13–15, 2015. The group continued to attack Amiriyat al-Fallujah and Garma thereafter. For more information on the Islamic State’s attacks west of Baghdad in June 2015, see the Iraq Situation Update series at the Institute for the Study of War.
[e] The Islamic State attacked Sinjar multiple times over the summer of 2015. The most recent attack at Sinjar occurred on September 1, 2015. “Peshmerga Repels an Attack and Causes Da`ish to Suffer Huge Losses in Shinkal,” PUK Media, September 1, 2015.
[f] The Islamic State may have used mustard gas against Peshmerga forces in Makhmour on August 11, 2015. Barbara Starr, Jim Scuitto, and Elise Labott, “U.S. investigating ‘credible’ reports ISIS used chemical weapons,” CNN, August 14, 2015; Tom Coghlan, “British troops in Iraq face rockets armed with chlorine gas,” UK News, August 14, 2015.
[g] The Islamic State reportedly shelled the northern Syrian town of Mare’a with mustard gas on September 1, 2015, followed by another attack with mustard gas on Hasaka city on September 2, 2015. Separate alleged mustard gas shellings also occurred on August 21-22, 2015. “Syria Direct: News Update 9-2-15,” Syria: Direct, September 2, 2015; “Da`ish Uses Chemical Weapons in Regions Under the YPG Control in Al-Hasakah,” Partiya Yekitiya Demokrat, September 1, 2015.
[h] Syrian YPG forces seized Serrin from the Islamic State on July 27, 2015, isolating its positions in Raqqa and Aleppo along one of two main roads. The Islamic State attempted to recapture the city over the summer. It remained in YPG hands as of September 2015; “Kurds cut key ISIL supply route in northern Syria: Monitor,” Agence France Presse, July 27, 2015.
[i] The Islamic State attacked Kurdish positions in Kobane, Tel Abyad, and Hasaka in response to the loss of Tel Abyad to the Syrian Kurdish YPG in June 2015. For more information, see “Military Situation in Northern Syria: June 25, 2015,” Institute for the Study of War, June 25, 2015.
[j] The Islamic State consistently paired attacks upon Ramadi and Baiji throughout the spring of 2015 while it was under counter-attack in Tikrit. For more information, see Jessica Lewis McFate, “The ISIS Defense in Iraq and Syria: Countering an Adaptive Enemy,” Institute for the Study of War, May 2015.
[k] The Islamic State attacked and seized much of Baiji beginning in May 2015, contesting the area heavily throughout the summer. The Islamic State’s most recent attack into Baiji occurred on September 19, 2015, when it attacked the ISF in the Baiji Oil Refinery with two SVBIEDS, which triggered a large fire. “Two Suicide Explosions and Battles Caused Killing or Injury of Four Security Members and a Huge Fire in Baiji Refinery,” Shafaq News, September 19, 2015.
[l] The Islamic State attacked Haditha on numerous occasions over the summer of 2015. The Islamic State’s most recent attack into Haditha occurred on September 3, 2015, when its forces targeted Barwana south of the city. The Islamic State failed to break the ISF’s defenses. “The War Media: 101 Da`ish Die During Military Operations on Thursday,” Shafaq News, September 3, 2015.
[m] For example, on August 15, 2015 Iraqi Army units conducted operations against Islamic State fighters preparing to attack the Ajil and Alas oil fields with VBIEDs. “67 Da`ish Die in Pre-emptive Operation East of Tikrit,” Al-Mada Press, August 15, 2015.
[n] The Islamic State claimed via social media outlets to have seized the Jezal oil fields north of Palmyra on September 6, 2015, reports that were picked up by several other local sources. The Assad regime reportedly counterattacked on September 9, 2015. The area is assessed to remain contested as of September 2015. “The [Islamic] State Declares Its Control Over Jazal Village and Continues Besieging Oil Field,” Zaman al-Wasl, September 7, 2015; “Da`ish Controls Jazal and Besieges the Regime’s Soldiers in Its Oil Field East Homs,” All4Syria, September 7, 2015.
[o] The Islamic State deployed many fighters to Deir ez-Zour from eastern Syria and Anbar for an offensive against the regime-held neighborhoods of Jourah and Qasour on September 22-23, 2015. “Military Uses High Level Equipment to Expel the Regime from Dir Al-Zur,” All4Syria, September 23, 2015; “ISIS mobilizes for large Deir Ezzor battle,” NOW, September 23, 2015.
[p] “Systematic Islamic State car bombings wreak destruction in north Aleppo,” Syria: Direct, September 14, 2015. The Islamic State conducted attacks against Syrian rebel positions north of Aleppo city in late summer, including Mare’a. One rebel commander claimed the Islamic State had conducted up to 23 VBIED attacks against Mare’a in recent weeks. The group is likely attempting to generate new border access west of the Free Zone. For more information, please contact the author.
[q] Syrian rebels in Idlib reported a series of assassinations over the summer. Attribution is not clear, but the Islamic State may be trying to create conditions intended to help reestablish access to Turkey. The last reported attack against a Dar al-Qada Courthouse affiliated with Jabhat al-Nusra in Salqin, Idlib province was an SVEST (suicide vest) on August 30, 2015. “Suicide attack kills 13 and leaves injuries in Salqin city,” Syrian Observatory for Human Rights, August 30, 2015; “Idlib: Suicide Bomber Kills or Injures 17 Individuals in Salqin,” Zaman al-Wasl, August 30, 2015.
[r] Unknown gunmen assassinated the vice president of the Dar al-Adel Courthouse, a rebel structure, in Dera’a city on September 2, 2015. The attack is likely the work of the Islamic State. The group’s presence in southern Syria has been limited, but Dera’a province is another-border route that the Islamic State may pursue in 2015-2016. “Deputy Chief of Dar Al-`Adel Court is Assassinated in Huran.” All4Syria, September 2, 2015.
[s] The Islamic State reportedly clashed with Hezbollah and regime soldiers near the Lebanese border crossing with Qusayr in southern Homs province on August 18, 2015. “ISIS attacks Hezbollah near north Lebanon border,” NOW, August 18, 2015; “Islamic State 2.5 km from Lebanon,” Syria Direct, August 18, 2015.
[t] The Islamic State claimed on September 23, 2015 to have seized parts of the highway between Homs city and the T4 airbase, which would isolate the city from both the east and the west. The Islamic State overran Qurayatayn on August 5, 2015, providing access to the airbase. “The Islamic State Continues its Attack on Al-Qaryatayn City,” Syrian Observatory of Human Rights, August 5, 2015; “Da`ish Imposes Its Control on Al-Qaryatayn City,” All4Syria, August 5, 2015.
[u] A series of explosions in Homs city have been claimed by both Jabhat al-Nusra and the Islamic State. It is unclear if both groups are conducting the attacks. The last blast claimed by one or both groups was an IED that detonated on a civilian bus on September 23, 2015. “For the second consecutive day, explosions rock the city of Homs leaving casualties,” Syrian Observatory for Human Rights, September 23, 2015; “Da`ish Announces Attacks on Third Military Airport and VBIEDs Strikes Homs Neighborhood Again,” All4Syria, September 23, 2014.
[v] Syrian rebels had been achieving new inroads against the Syrian regime in Aleppo province, before Russian and Iranian assets began to mass for what appeared to be an impending offensive in Aleppo in October 2015. In the summer, rebels had made gains both by cutting regime supply lines south of the city and by seizing regime positions within Aleppo city. Most notably, rebels seized the regime’s base at the Scientific Research Center in northwestern Aleppo city on July 2, 2015. The rebel attack and the regime’s failed attempt to retake the facility were reported by numerous rebel groups via social media. For more information on Syrian rebel social media, contact the author.
[w] A Syrian rebel group called Jaysh al-Islam claimed to seize more than 20 regime military positions north of Damascus on September 13, 2015, severing a regime supply route north from Damascus. “Conflicts on the Outskirts of Al-Asad Town.” Zaman al-Wasl, September 13, 2015.
[x] The Islamic State conducted an extremely high casualty VBIED in Khan Bani Saad in Diyala province on the last day of Ramadan 2015. The attack killed 120 and injured 140. It was followed by two additional very high casualty VBIEDS in Sadr City in Baghdad the following week. The use of single-truck SVBIEDS with this amount of explosive power is a trend, compared to the previous waves of many small VBIEDS that used to be prevalent in Baghdad. Mohammed Tawfeeq and Steve Almasy, “ISIS claims responsibility for Iraq bombing that killed more than 80,” CNN, July 18, 2015; “Islamic State claims car bomb that kills more than 100 in Iraq,” Reuters, July 18, 2015.
[y] The Islamic State launched many attacks over the summer of 2015 upon Karbala and Nukhaib (west of Karbala). The first and most spectacular was a wave of eight VBIEDs that were intercepted in Nukhaib by the ISF on June 10, 2015, a week before Ramadan 2015 began. “Defense [Ministry]: Captures 8 VBIEDs with Their Drivers in Al- Nukhaib and Destroys Trucks Loaded with Barrels Belong to Da`ish in Al-Fallujah,” Shafaaq News, June 10, 2015; “Al-Hashd Al-Sha`bi Confirms Capturing 7 VBIEDs West Karbala’ Coming from Al-Anbar,” Al-Mada Press, June 10, 2015; “Forces Capture 7 VBIEDs in Karbala That Carry Refugees,” All Iraq News, June 10, 2015.
[z] The Islamic State attempted several attacks against Samarra over the summer of 2015. One recent example was a VBIED, which the ISF and “Popular Mobilization Units” destroyed in al-Hweish, west of Samarra on August 20, 2015. “27 Members of the Security Forces and Hash Were Injured in the Explosion of an Explosive Oil Tanker West Samara,” Al Sumaria, August 20, 2015. The Islamic State also claimed through its official social media that it launched an operation called the “Campaign of Shaykh Abu Khattab al-Shayhawi” on August 14, 2015 in Salah ad Din, including references to its attacks in Samarra as well as Tikrit and Baiji. For more information on the Islamic State’s social media operations, contact the author.
[aa] Shi’a militias guarding Samarra claimed to launch several offensives to clear the Islamic State from the desert west of Samarra over the summer of 2015. Most recently, the ISF announced its own operation to clear the area on September 18, 2015. The area is a historic safe haven for the Islamic State and will likely be difficult to clear permanently. “Forces Clear Al-Tharthar Region and Kill Dozens of Da`ish,” al-Mada Press, September 19, 2015.
 “‘More than 90%’ of Russian airstrikes have not targeted ISIS, US says,” Guardian (U.K.), October 7, 2015.
 Harleen Gambhir, “ISIS’s Global Strategy: A Wargame,” Institute for the Study of War, July 2015.
 For more information on the Islamic State’s objectives in Syria, which largely resemble its objectives in Iraq, see Christopher Kozak, Jennifer Cafarella, and Genevieve Casagrande, “Syria Forecast,” Institute for the Study of War, September 2015.
 “ISIS seized ground from Aleppo rebels under cover of Russian airstrikes,” Guardian (U.K.), October 9, 2015; “ISIS Advances near Syria’s Aleppo despite Russian Airstrikes,” Associated Press, October 9, 2015.
 Michael Knights and Alexandre Mello, “The Cult of the Offensive: The Islamic State on Defense,” CTC Sentinel (8:4), West Point, New York, 2015.
 For more information on the Islamic State’s defensive strategy, see Jessica Lewis McFate, “The ISIS Defense in Iraq and Syria: Countering an Adaptive Enemy,” Institute for the Study of War, May 2015.
 For more information on how the Islamic State seized Ramadi in May 2015, see Patrick Martin, “ISIS Captures Ramadi,” Institute for the Study of War, May 18, 2015.
 “Fallujah Operation Key to Liberating Anbar,” Al-Monitor, July 13, 2015; Dominic Evans, “Iraq Launches Offensive to Drive Islamic State from Biggest Province,” Reuters, July 13, 2015.
 Michael Knights and Alexandre Mello, “The Cult of the Offensive: The Islamic State on Defense.”
 “Operation Inherent Resolve Targeted Operations Against ISIL Terrorists,” U.S. Department of Defense, September 22, 2015.
 Ahmed Rasheed and Ned Parker, “In Mosul, Islamic State turns captured city into fortress,” Reuters, January 22, 2015; Aso Mohammed, “Iraqi Defense: ISIS puts ‘Caliphate fences’ around Mosul,” Rudaw, March 19, 2015.
 For more information on the Islamic State’s failed Kobane offensive, see Jessica Lewis McFate, “The ISIS Defense in Iraq and Syria: Countering an Adaptive Enemy,” Institute for the Study of War, May 2015.
 For more information on how the YPG seized Tel Abyad from the Islamic State in June 2015, see Christopher Kozak and Genevieve Casagrande, “The YPG Campaign for Tel Abyad and ar-Raqqa,” Institute for the Study of War, June 17, 2015.
 Charles C Caris and Samuel Reynolds, “ISIS Governance in Syria,” Institute for the Study of War, July 2014.
 “Islamic State conflict: Kurds ‘capture Syrian town north of Raqqa,’” BBC, June 23, 2015; Tom Perry and Laila Bassam, “Syria Kurds seize town from Islamic State near its ‘capital,’” Reuters, June 23, 2015.
 General Lloyd Austin, “Testimony on “U.S. Military Operations to Counter the Islamic State in Iraq and the Levant,” United States Senate Committee on Armed Services, September 16, 2015; “Martha Raddatz Interviews General John Allen: Full Transcript,” ABC News, September 11, 2015.
 Abu Mohammed, “Signs of Compulsory Recruitment in Raqqa,” Raqqa is Being Slaughtered Silently Blog, October 15, 2015.
 “About 200 Detailed by IS Militants after Protest in Western Iraq,” Radio Free Europe Radio Liberty, August 31, 2015.
 “Da`ish Kills a Number of the Preachers and Imamas of Al-Hawijah,” al-Ghad Press, September 18, 2015; “Da`ish Kidnaps 10 Preachers and Imams of Al-Hawija Because of Their Refusal to Renew Their Bay`a to Al-Baghdadi,” al-Sumaria, September 18, 2015.
 “ISIS finance minister killed in Mosul ambush,” Rudaw, June 23, 2015; “40 Da`ish VBIEDs Making Experts in Airstrike on Bomb Workshop in Al-Mosul,” All Iraq News, June 24, 2015
 Hamdi Alkhshali, Jomama Karadsheh, and Don Melvin, “ISIS’ legacy in Tikrit: Booby traps, IEDs, and fear,” CNN, April 2, 2015; Ron Nordland, “Iraq Forces, Pushing ISIS Out of Tikrit, Give Few Thanks to Airstrikes,” New York Times, April 2, 2015.
 For more information on how the Islamic State seized Palmyra in May 2015, see Christopher Kozak, “New ISIS Offensives in the Syrian War,” Institute for the Study of War, May 14, 2015.
 Hugo Spaulding et al, “Russian Deployment to Syria: Putin’s Middle East Game-changer,” Institute for the Study of War and AllSource Analysis, September 2015
 Anne Barnard, Michael R. Gordon, and Eric Schmitt, “Turkey and U.S. Plan to Create a ‘Safe Zone’ Free of ISIS,” New York Times, July 27, 2015; Anne Barnard and Michael R. Gordon, “Goals Diverge and Perils Remain as U.S. and Turkey take on ISIS,” New York Times, July 27, 2015.
 For more information on Syrian rebels’ northern Latakia offensive, see Christopher Kozak, “Syrian Rebel Forces Pressure Regime Heartland,” Institute for the Study of War, August 20, 2015.
 Theodore Bell et al, “Iraq’s Prime Minister Fights to Control Government,” Institute for the Study of War, August 10, 2015.
 Kimberly Kagan, “Iranian Proxy Militia Leaders Pose Threat to PM Abadi’s reforms,” Institute for the Study of War, September 3, 2015; Sinan Adnan, “Kata’ib Hezbollah and Iranian Proxies Challenge Iraq’s National Guard Law,” Institute for the Study of War, September 8, 2015.
 Sinan Adnan, “Regional conflict between Iraq and Turkey manifests in Iraq,” Institute for the Study of War, September 12, 2015.
 “Al-Zubayr Committee Announces the Killing or Injury of 35 Individuals in Al-Zubayr Explosion,” Al Mada Press, October 5, 2015. The Islamic State claimed the attack in Basra on October 5, 2015. For more information on the Islamic State’s use of social media, contact the author.
 Christopher Kozak, “Turkey Expands Campaign against ISIS and the PKK,” Institute for the Study of War, July 25, 2015.
 Vladimir Isachenkov, “Putin hopes to steal UN show with Syria-focused speech,” Associated Press, September 24, 2015.
 Aaron Zelin, “The Islamic State’s Burgeoning Capital in Sirte, Libya,” The Washington Institute for Near East Policy, August 6, 2015.
 Saagar Enjeti and Lauren McNally, “Militant Attack and Support Zones in Afghanistan,” Institute for the Study of War, September 15, 2015.
 Harleen Gambhir, “ISIS’s Global Strategy map,” Institute for the Study of War, September 2015; Harleen Gambhir, “ISIS-Linked Regional Activity in July 2015,” Institute for the Study of War, August 7, 2015.