Aaron Stein

The U.S.-backed effort to territorially defeat Daesh (ISIS) has grown more complicated in recent weeks, despite considerable progress to liberate Raqqa from Daesh. The Syrian regime’s capture of much of Deir al-Zor province in early September brought regime, Russian, and Iranian elements into proximity to the U.S.-backed Syrian Democratic Forces, a multiethnic umbrella group dominated by the Kurdish YPG. In response to the regime’s advance, the SDF announced the start of “Jazeera Storm,” an offensive to consolidate control over the countryside east of the Euphrates River. The SDF offensive began before the United States and Russia had agreed on a specific mechanism for military deconfliction, similar to arrangements reached to manage combat operations around Al-Tanf in southern Syria and Tabqa, the SDF controlled town just south of the Euphrates.

The U.S. appeared to be relying on an informal understanding, wherein the Euphrates River would divide the zones of control: Russia and the regime to the south and west and the U.S. and SDF to the north and east. The U.S.-Russian deconfliction arrangement relies on direct communication between the United States’ Combined Air Operations Center in Qatar and Russia’s military base in Latakia, Syria. The arrangement has worked well, with both sides exchanging information to manage the two sides’ independent bombing in Syria.

However, the exchanges do not necessarily mean that a formal understanding about “lines in the sand” has been reached. For Russia and the regime, a neat dividing line separating a regime controlled Deir al-Zor city makes little sense. The city straddles the Euphrates, although in September the regime managed to secure both the east and west sides of the city from Daesh. The SDF are approaching from the north and are within 10 km of the regime-held territory. In the event of conflict with the SDF, the city would be vulnerable to artillery and rocket attack from across the river. Moreover, Syrian oil resources and the region’s largest population centers are on the northwest side of the river, while Mayadeen, a Daesh stronghold the U.S. wants to liberate, is on the river’s western bank. Russia and the regime have an incentive to set the deconfliction line some 20 kilometers northeast of the Euphrates River, out to the Iraqi border, while the U.S. would like to horse trade over territory to ensure that the SDF takes Mayadeen. The SDF similarly covets control over the resources on the northeast of the river and has pledged to continue moving down the Euphrates River Valley, a scenario that challenges regime interests and risks further U.S.-Russian tensions, independent of U.S. goals for Mayadeen.

The absence of a clear deconfliction line runs the risk of unintended escalation between U.S. and Russian forces. On Sept. 16, Russian aircraft, operating in close proximity to their U.S. counterparts, bombed SDF positions near Deir al-Zor city. The strike injured six SDF members and was near U.S. ground forces. The details about the strike remain fuzzy, including whether Russia deliberately struck the SDF, or simply made a targeting error. The second risk stems from the regime’s future intentions vis-à-vis the SDF. This leaves three main scenarios: The two sides can reach a separate political arrangement, permanently freeze conflict, or, in the absence of a political settlement, the regime uses force to take back territory lost.

The implications for any of these scenarios will have an impact on how the U.S. beings to plan its withdraw from Syria, independent of the Daesh challenge, which could also result in a continued military presence in country. The U.S. campaign against Daesh is territorially focused and intended to force the group from the areas it controls. The group’s territorial defeat is a foregone conclusion. However, the group’s predecessor in Iraq, the Islamic State in Iraq, demonstrated the capability to oversee an insurgency and a skeleton bureaucratic structure, even at the height of the “surge” in Iraq, the post-2007 increase in U.S. forces, and the height of the Sunni resistance to Daesh Iraq. The expectation in Syria is that Daesh will morph back into an insurgency and continue to carry out attacks in Syria and Iraq, similar to the actions of its predecessor organization in Iraq less than a decade before.

To deal with the insurgency, U.S. policymakers and independent think tanks, steeped in the lessons of the Iraq surge, tend to make two interrelated arguments. First, the Kurdish dominated SDF is ill equipped to navigate Arab-Sunni politics in eastern Syria, and that the specter of Kurdish oppression will fuel Arab-Sunni resentment, which benefits Daesh recruitment. Second, a regime offensive would have similar consequences for the region’s Sunni population, while at the same also allowing for Iran to deepen its presence on the Iraqi border. The Iranians, then, will have control over a land corridor stretching between Tehran and Beirut, which would allow for the movement of weapons to Hezbollah.

The U.S. has settled on using the SDF model to try and address both of the aforementioned issues. The U.S. has steadfastly sought to expand the number of Arabs fighting under the SDF’s umbrella and intends to use these groups to spearhead an offensive along the Euphrates River and out to the Iraqi border. The Arab SDF groups would then take over governance, albeit under the ultimate control of Syrian Kurdish authorities. If successful, the U.S. will have territorially defeated Daesh, prevented Iran and the regime from taking control of the Iraqi-Syrian border, and helped to install a semblance of local Sunni Arab-majority rule.

The challenge is that the further expansion of SDF control is at odds with regime and Russian interests, and, thus, the regime could use force to block the SDF. The U.S. would have to make a choice about whether it intends to defend the SDF from regime attack. The regime could also make a dash to the border from a beachhead on the east side of the river, near Deir al-Zor city. The U.S., then, would have to make a choice: Participate in a “race” with the regime, largely to block Iranian expansion, or sit back and watch it happen. If the U.S. decides to challenge Iran, the options for military withdrawal from Syria grow more complicated. A counter-Iran strategy requires that the U.S. Air Force protect U.S. troops on the ground from attack, requiring a sustained presence, lest premature withdrawal simply allow for the regime and its allies to take territory the United States vacates.

The “sit back and do nothing” strategy also carries similar risks, absent a clear understanding of regime and Iranian intent vis-à-vis the SDF. The SDF could stop all combat operations after Raqqa, but will still be left in control over much of northeast Syria – and the regime will have to make a choice about what to do about it. Thus, absent a negotiated settlement, the United States may decide to stay to protect its partner force from external attack or as a bulwark against Iranian expansion until the civil conflict comes to an end.

These twin challenges are independent of the expected Daesh insurgency problem, which will also complicate a U.S. exit from Syria. The territorial defeat of Daesh will not ensure that the group’s leaders have been eliminated. The specialized U.S. Special Operations Task Force charged with targeting the group’s leadership could then stay to continue carrying out strikes on high-value-targets. This strategy would also help to combat the expected Daesh insurgency, resulting in an open-ended commitment to continue the counterterrorism mission in Syria long after the physical caliphate crumbles.

As a first step, the U.S. and Russia have ample incentives to finalize a clearer line of deconfliction to prevent unintended escalation. To begin crafting an exit strategy, the U.S. must discern regime intent toward the SDF, and whether the two sides can reconcile any differences and come to a political arrangement. The U.S. must also articulate what role Bashar Assad will have in any such negotiations and whether the benefits of beating Iran and its militias to the border is worth the open-ended military commitment that “winning” would entail.

None of the above questions can be answered without first answering the basic policy questions of what does the U.S. want in Syria: What is the U.S. policy on Assad? Iran? What is it that the U.S. wants in post-conflict Syria? How does that goal fit in with the myriad of external actors that will have a say over the final peace agreement. Answering this requires asking hard questions about whether it is wise for the U.S. to maintain an open-ended presence in Syria, amid the global demands on finite military resources.

The territorial defeat of Daesh is inevitable, but the withdrawal of U.S. forces requires policymakers to grapple with difficult questions that, as of now, remain unanswered. The U.S. will not be able to dictate outcomes in Syria and will not get everything it wants. However, a coherent exit strategy requires making hard choices about U.S. interests and how those fit into the broader kaleidoscope of competing actors in Syria’s civil conflict, and measure those conclusions against U.S. foreign policy goals around the world.