ISIS currently faces an unprecedented threat to its core terrain in Northern Syria from an array of competing actors. The U.S.-backed Syrian Democratic Forces surrounded the key transit hub of Manbij in Eastern Aleppo Province on June 9, threatening to sever the last remaining supply lines available to ISIS over the Syrian-Turkish Border. Meanwhile, ISIS’s stronghold of Ar-Raqqa City faces mounting pressure as both the U.S.-led coalition and pro-regime forces advance into its countryside. These combined pressures forced ISIS to withdraw from its frontlines with opposition forces in Northern Aleppo Province in order to prioritize the defense of its core terrain. Nonetheless, the degrading position of ISIS in Northern Syria is poised to ignite further conflict between local and regional actors that may jeopardize future successes. The terrain vacated by ISIS will likely host renewed competition between Syrian Kurds, opposition groups, and pro-regime forces as well as a geopolitical struggle involving Turkey, Syria, Russia, and the U.S. These conflicts could strain the international anti-ISIS coalition and stall further progress against ISIS in Syria unless the U.S. can successful navigate the conflicting interests of its allies and adversaries in the region.

Introduction

ISIS currently faces unprecedented pressure in Northern Syria. The U.S.-led anti-ISIS coalition has long pursued a campaign to isolate and ultimately seize Ar-Raqqa City – the de-facto capital of ISIS in Syria. This strategy has included several separate lines of effort over the past twelve months to sever the ground lines of communication linking Ar-Raqqa City to Mosul in Iraq as well as the Syrian-Turkish Border. These cumulative efforts planted the seeds for actors on the ground to achieve nonlinear effects against the organization. Over the past ten weeks, an array of groups, including Syrian Kurds backed by the U.S., Sunni Arabs backed by Turkey, and the Syrian Arab Army backed by Russia and Iran, have exploited these vulnerabilities to varying degrees. ISIS will likely lose access to its cross-border flows of foreign fighters and supplies over the near-term, leaving the organization vulnerable throughout its core terrain in Iraq and Syria. Nonetheless, the ongoing successes against ISIS in Northern Syria remain uncoordinated and localized. The major factions active on the ground view each other with hostility and often operate at cross-purposes to one another. The competing actors also aim to leverage their independent campaigns in Northern Syria to their own ends despite their ostensible shared goal to defeat ISIS in Syria. The Syrian Kurds harbor ambitions to unite their disparate cantons and construct a contiguous autonomous zone upon terrain formerly held by ISIS along the Syrian-Turkish Border; Turkey aims to use its network of allied opposition groups to check the Syrian Kurds and block their future expansion; and the regime and its allies hope to exploit anti-ISIS operations in order to reassert their claims to domestic rule and international legitimacy. These competing motives and actions set the stage for future conflict that could strain the international anti-ISIS coalition and allow ISIS to preserve its control of terrain along the Euphrates River Valley in Eastern Syria over the long-term.

The Competing Actors

The Syrian Democratic Forces

The Syrian Democratic Forces – a U.S.-backed coalition consisting of the Syrian Kurdish YPG and allied opposition groups – represents the primary ground partner in the fight against ISIS in Syria. The U.S. began providing direct air support to the Syrian Kurdish YPG in September 2014 in order to blunt an ISIS offensive on the border town of Kobani (Ayn al-Arab) in Eastern Aleppo Province. The military partnership continued to expand over time as the Syrian Kurdish YPG demonstrated its effectiveness against ISIS on the battlefield. U.S. President Barack Obama authorized the deployment of up to fifty U.S. Special Operations Forces soldiers to Northern Syria in October 2015 in order to “train, advise, and assist” the Syrian Kurdish YPG as well as allied tribal and opposition groups in the so-called Syrian Arab Coalition as part of the newly-formed Syrian Democratic Forces. This deployment occurred despite long-standing reservations from Turkey, which considers the Syrian Kurdish YPG to be a terrorist organization due to its links to the Kurdistan Workers’ Party (PKK). By the end of 2015, the Syrian Democratic Forces controlled the majority of the Syrian-Turkish Border and occupied a bridgehead across the Euphrates River at the Tishreen Dam.

The U.S. intensified its cooperation with Syrian Democratic Forces in early 2016 in order to accelerate operations aimed at isolating and seizing the ISIS stronghold of Ar-Raqqa City. The U.S. expanded its deployment of Special Operations Forces by anadditional 250 personnel in April 2016. U.S. Special Envoy to the Anti-ISIS Coalition Brett McGurk later stated on May 15 that a “pressure campaign” on Ar-Raqqa City would begin over the “coming weeks and months.” U.S. CENTCOM Commander Gen. Joseph Votel later conducted an unannounced visit to Northern Syria on May 21 in order to review campaign plans with the leaders of the Syrian Democratic Forces and the affiliated Syrian Arab Coalition. These efforts laid the groundwork for the start of a new phase of the anti-ISIS campaign on the ground. On May 24, the Syrian Democratic Forces announced an operation to “liberate” the northern countryside of the ISIS stronghold of Ar-Raqqa City. The Syrian Democratic Forces achieved initial gains despite the presence of a large number of IEDs and later expanded the operation to target the town of Tabaqa west of Ar-Raqqa City on May 30, although a spokesperson clarified that the ongoing offensive did not aim to contest the city itself.

The looming territorial expansion of the Syrian Kurds in Northern Syria prompted fierce resistance in Turkey. Deputy Chief of the Turkish General Staff Gen. Yasar Guler reportedly warned U.S. CENTCOM Commander Gen. Joseph Votel after his visit to Northern Syria that the Syrian Kurdish YPG would “let him down when the fight gets tough” and urged the U.S. to expand its support to Turkish-backed opposition groups in Northern Aleppo Province. On May 25, tensions flared further after the release of photographs showing U.S. Special Operations Forces in Northern Syria wearing the shoulder patches of the Syrian Kurdish YPG. Turkish Foreign Minister Mevlut Cavusoglu denounced the incident as an “unacceptable…double standard” while Turkish President Recep Erdogan stressed that the images illustrated the “wrong steps” being taken in cooperation with “terrorist groups.” The U.S. ordered its soldiers to remove the patches within days, but the vast gap between the positions of the two countries remained clear. On May 30, Turkey proposed a joint deployment of Special Operations Forces with the U.S. and other allies to clear ISIS from the Syrian-Turkish Border and open a “second front” against ISIS in Ar-Raqqa City on the condition that the coalition embed with local opposition groups rather than the Syrian Kurdish YPG. These plans failed to gain traction.

The operation in Northern Ar-Raqqa Province that provoked the ire of Turkey nonetheless obscured the true objective of the Syrian Democratic Forces – the key town of Manbij in Eastern Aleppo Province. Manbij serves as ISIS’s main “transit hub for foreign fighter flows” as well as a base for its international terrorist attacks. The seizure of the town also serves the overall strategic objective to isolate Ar-Raqqa City from its last remaining supply routes to the Syrian-Turkish Border. On May 31, the Syrian Democratic Forces advanced on Manbij from the direction of their beachhead at the Tishreen Dam. At the same time, a separate detachment conducted a forced crossing of the Euphrates River and repaired the Qarah Qawzaq Bridge, opening a new front east of Manbij. These forces converged on Manbij with the support of coalition airstrikes and successfully isolated the town from three sides on June 9, placing ISIS under severe pressure even as the Syrian Democratic Forces vowed that the campaign would continue “until the liberation of the last inch of land in Manbij and its rural areas.” U.S. officials stressed that the design of the operation minimized the participation of the Syrian Kurdish YPG in accordance with the concerns held by Turkey. Operation Inherent Resolve Spokesperson Col. Chris Garver stated that “local Arabs” comprised approximately 85% of the 3,000 fighters participating in the operation.

Turkey responded cautiously to the ongoing offensive on Manbij. Turkish Deputy Prime Minister Numan Kurtulmus stated on May 31 that the potential expansion of the Syrian Kurdish YPG west of the Euphrates River “constitutes a national security line for Turkey” and that Turkey rejected any military participation in the operation as “out of question.” Nonetheless, President Erdogan acknowledged on June 2 that roughly 2,500 of the 3,000 fighters participating in the operation are Sunni Arabs with Syrian Kurds operating as a “logistical force.” Foreign Minister Cavusoglu later stated on June 7 that the U.S. had “given a guarantee” that the Syrian Kurdish YPG would withdraw east of the Euphrates River after the completion of the operation to seize Manbij. If implemented, these concessions will likely prove sufficient to prevent Turkey from acting to undermine the operation. Nonetheless, it remains an open question whether the Syrian Kurdish YPG intends to honor the deal given its long-term strategic objective to unite all of its cantons along the Syrian-Turkish Border.

Northern Aleppo Opposition Groups

The loose coalition of Sunni Arab opposition groups supported by Turkey in Northern Aleppo Province constitutes another key group of actors engaging in anti-ISIS operations in Northern Syria. These groups span a wide ideological range – from Free Syrian Army (FSA)-affiliated moderate secularists to Islamists linked with the Muslim Brotherhood to Salafi-Jihadist group Ahrar al-Sham – but remain united in their opposition to ISIS. The groups contain a large number of local fighters with a strong motivation to defend their hometowns, particularly the key urban centers of Mare’a and Azaz. Northern Aleppo Province thus represents potential fertile ground for the development of a Sunni Arab partner against ISIS. The U.S. Department of Defense attempted to mobilize this community in an ill-fated ‘train-and-equip’ program that ended in October 2015. The U.S. has since provided training to “dozens” of fighters in Northern Aleppo Province as part of a restructured ‘train-and-equip’ programthat embedded these fighters with several smaller factions along the so-called Mare’a Line, including Liwa al-Hamza, Liwa 99, and Liwa al-Mutasem.

Turkey has promoted support for Turkmens, Islamists, and other opposition groups in Northern Aleppo Province as a counterweight to further expansion by the Syrian Kurdish YPG. Turkey allowed several hundred opposition fighters to transit through its territory from Idlib Province in order to reinforce Mare’a and Azaz amidst a pro-regime offensive on the region in February 2016. Turkey also provided the opposition in Northern Aleppo Province with fresh supplies of mortars, rockets, and other munitions over the same time period. Former Turkish Prime Minster Ahmet Davutoglu stressed on February 18 that “the whole world should know…we will not allow Azaz to fall.” Meanwhile, Turkey pressed the U.S. and other coalition allies to expand their own support for the opposition in Northern Aleppo Province. For example, President Erdogan previously conditioned his support for the operation to seize Manbij in Eastern Aleppo Province upon the expansion of the coalition air campaign along the Mare’a Line.

These lobbying efforts led the U.S. to provide its support to an opposition-led offensive to clear ISIS from the Syrian-Turkish Border. On April 7, the Hawar Kilis Operations Room – a coalition of opposition groups that included fighters vetted by the ‘train-and-equip’ program – seized the ISIS-held border town of Al-Rai in Northern Aleppo Province with the aid of cross-border artillery fire and coalition airstrikes. The advance severed a key route for smuggling foreign fighters and supplies, and left ISIS with little more than thirty miles of remaining border access. The rapid offensive along the border nonetheless left opposition forces vulnerable to an attack on their exposed southern flank. ISIS launched a two-pronged counteroffensive on April 10 - 14, recapturing the town of Al-Rai and temporarily entrapping opposition groups in a pocket along the Syrian-Turkish Border. The opposition continued to suffer a steady erosion in terrain over subsequent weeks, culminating in a major attack by ISIS on May 27 that punctured the Mare’a Line and threatened to overwhelm remaining opposition forces in Mare’a and Azaz.

The reversal of opposition gains in Northern Aleppo Province stemmed from multiple sources. Opposition groups in Northern Aleppo Province remain divided and fractious despite the threat posed by ISIS, failing to unite around a single leader or strategic vision for the operation. The opposition also split its attention between multiple adversaries and engaged in several major clashes with the Syrian Kurdish YPG, including a failed attack on the town of Ayn Daqnah in April 2016 that killed at least sixty opposition fighters. Opposition sources also blamed their external backers for the setbacks, criticizing the U.S. for failing to provide key equipment - such as night-vision goggles, mine-clearing vehicles, and anti-tank weapons - that could counter the use of SVBIEDs and IEDs by ISIS. In a press briefing on May 13, former Operation Inherent Resolve Spokesperson Col. Steve Warren stated that the operation had ultimately been hindered by the limited capability of local “hold forces.”

The near-destruction of opposition groups in Northern Aleppo Province nonetheless generated significant impetus for the U.S. and Turkey to boost their capabilities on the ground. The U.S. expanded its military support to select opposition groups, conducting two much-needed airdrops of weapons and ammunition to Liwa al-Mutasem in Mare’a on June 2 and June 6. On June 7, Liwa al-Mutasem announced the integration of all opposition factions in Mare’a under its leadership, likely due in part from its status as an outlet for external support. Meanwhile, mounting pressure from the Syrian Democratic Forces at Manbij and Ar-Raqqa City forced ISIS to deprioritize its operations against the opposition. ISIS withdrew from large parts of Northern Aleppo Province on June 8, lifting the sieges of Mare’a and Azaz. The opposition – forged under the pressure of a relentless assault by ISIS - now sits in an optimal position to resume operations along the Syrian-Turkish Border under a unified leadership with strong external backing.

Pro-Regime Forces

The intensifying fight against ISIS in Northern Syria also motived Syrian President Bashar al-Assad and his foreign allies to escalate their own operations under the guise of the fight against terrorism. On June 2, the Syrian Arab Army and allied paramilitary forces supported by Russian aircraft launched an operation in the direction Ar-Raqqa City from the crossroads of Ithriya in Eastern Hama Province, taking advantage of the ongoing fight against ISIS in Manbij. Video footage showed large numbers of armored vehicles, multiple rocket launcher systems, and field artillery participating in the offensive. Pro-regime forces advanced rapidly along the open desert highway, entering the boundary of Ar-Raqqa Province on June 4 and seizing a key road junction roughly twenty miles from Tabaqa west of Ar-Raqqa City on June 7. On the same day, President Assad vowed to “liberate every inch of Syria” as part of the “war against terrorism” in a speech before the Syrian Parliament. ISIS responded to this pressure by deploying a column of reinforcements to Tabaqa from Ar-Raqqa City while mounting probing attacks to disrupt the regime ground line of communications further west.

Pro-regime forces likely remain incapable of seizing Ar-Raqqa City or other ISIS-held urban areas. The advance nonetheless allows the regime to stake its claim to Ar-Raqqa Province while positioning for follow-on operations to exploit further losses by ISIS at the hands of the Syrian Democratic Forces. The offensive also provides Syrian President Bashar al-Assad and Russian President Vladimir Putin with an opportunity to impose their strategic priorities on the U.S. and its coalition allies. Russian Foreign Minister Sergey Lavrov floated a proposal for the U.S. and Russia to coordinate operations against Ar-Raqqa City in March 2016. The U.S. flatly rejected this offer, but the presence of pro-regime forces outside of Ar-Raqqa City would at a minimum force the U.S. to engage in battlefield deconfliction – opening the door for Syria and Russia to message their role as valuable partners against ISIS before the international community.

Conclusion

The multi-sided fight for Northern Syria over the coming months will likely complicate efforts by the U.S. to maintain the focus and coherence of its local partners on the fight against ISIS. The Syrian Kurdish YPG maintains a long-term strategic objective to form a contiguous autonomous zone along the Syrian-Turkish Border, calling into question the ability of the U.S. to maintain its guarantees to Turkey. The Syrian Kurdish YPG could elect to establish a land corridor to the Afrin Canton in Northern Aleppo Province rather than press the fight against Ar-Raqqa City – a move that could find support from Russia. This decision would likely provoke significant military retaliation from both Turkey and local opposition groups, fracturing the tenuous coalition of anti-ISIS actors in Northern Syria. Even in a best-case scenario, Northern Aleppo Province will likely constitute a venue for continued skirmishes between Sunni Arabs and Syrian Kurds stemming from historical rivalries, ethnic tensions, and foreign interference by Turkey.

Meanwhile, pro-regime forces remain positioned to exploit gains against ISIS for their own ends. Pro-regime forces sit outside the key urban centers of Al-Bab in Aleppo Province and Tabaqa in Ar-Raqqa Province in anticipation of future opportunities to secure new terrain and broadcast their claims of effectiveness in the “war against terrorism.” The decision to prioritize these efforts reflects the overriding strategic aim shared by Syria, Russia, and Iran – namely, the expulsion of the U.S. and all vestiges of its influence in the region. This objective provides pro-regime forces with an incentive to subvert and undermine the international coalition against ISIS in favor of their own regional security structures. At the same time, the campaign for Northern Syria will open new opportunities for Russia to threaten Turkey and thereby pressure the southern flank of NATO. Russia has expressed interest in expanding its ties with the Syrian Kurdish YPG in Northern Syria and faces accusations of providing material support including man-portable air defense systems (MANPADS) to the Kurdistan Workers’ Party (PKK) insurgency in Turkey. A competition for control over Northern Syria will provide Russian President Vladimir Putin with additional avenues to pursue this policy.

At the same time, the campaign in Northern Syria remains insufficient to defeat ISIS over the long-term. The seizure of key terrain along the Syrian-Turkish Border in Aleppo Province will deny ISIS easy access to the flow of foreign fighters and supplies that replenish its forces and bolster the staying power of its so-called ‘caliphate’. Nonetheless, local forces on the ground remain incapable of seizing ISIS’s stronghold of Ar-Raqqa City over the near-term. Neither the Syrian Democratic Forces nor pro-regime forces possess the forces necessary to contest the urban terrain of the city itself without mustering new recruits and risking overextension on other battlefronts. This constraint will be exacerbated by any military competition over terrain formerly held by ISIS in Aleppo Province. Moreover, the fall of Ar-Raqqa City remains insufficient to defeat ISIS along the remainder of the Euphrates River Valley. ISIS thus stands to maintain its presence in Eastern Syria over the long-term despite – or perhaps, because of – the multiple forces arrayed against it.