An outbreak of Arab-Kurdish violence threatens to upset the delicate balance that kept the Islamic State and other U.S. adversaries at bay.

Since 2017, Washington has managed to prevent the Islamic State’s resurgence and check Iranian and Russian expansion, all while maintaining a limited military footprint. It has done so by working with the Syrian Democratic Forces, an unstable coalition of partners fraught with internal rivalries. Now, the first cracks in that coalition have begun to emerge.

Earlier this month, the Kurdish-dominated Syrian Democratic Forces (SDF) narrowly survived the biggest blow to its rule since the group was formed in 2015. From Aug. 27 to Sept. 6, thousands of Arab tribesmen expelled the SDF from dozens of cities and towns in Syria’s eastern Deir Ezzor province in clashes that left anywhere from 150 to more than 350 people dead.

Deir Ezzor is divided by the Euphrates River into northern and southern halves, with the SDF and the regime of Bashar al-Assad controlling the former and latter areas, respectively. The northern half is the only part of SDF-controlled Syria that has no indigenous Kurdish population, making it more difficult for the group to govern than any other area of the country.
Northern Deir Ezzor is also home to the largest number of Syrian oil and gas fields, putting it in the crosshairs of the Assad regime and its Iranian and Russian backers, which have long sought to recapture the area and its valuable energy reserves.

The Islamic State is also more active in Deir Ezzor than any other area of the country, extorting large sums of money from oil merchants that the group uses to self-finance and carrying out near-weekly attacks on both sides of the Euphrates. Its location along Syria’s border with Iraq also makes Deir Ezzor important for both Iran and the Islamic State, which use the area to smuggle weapons and personnel across the region.

Amid this intense competition between outside forces, local tribes in northern Deir Ezzor have long felt overlooked and accuse the SDF of diverting revenues from the region’s oil and gas fields to areas with a larger Kurdish population.
The tribal rebellion earlier this month was an attempt by local leader Ibrahim al-Hifl and others to seize control of the area and compel the United States—which backs the SDF—to recognize the creation of an autonomous Arab statelet in northern Deir Ezzor, independent of both the SDF and Assad regime.

However, aside from generic calls for restraint, U.S. military and diplomatic officials remained largely silent during the fighting, afraid to publicly take sides in a conflict between two groups that Washington desperately needs to work together to prevent an Islamic State resurgence.

Many of those who took part in the early days of uprising were members of the Deir Ezzor Military Council (DEMC), the local SDF governing arm that administers the region on its behalf and is subordinate to the group’s Kurdish-dominated leadership. Since 2017, the DEMC has fought the Islamic State alongside the SDF and been indispensable in helping the latter form alliances in the area. However, the violent events earlier this month threaten to ruin this partnership and sabotage the SDF’s ties to local communities.
Though the SDF appears to have quelled the rebellion, in so doing it has killed, imprisoned, or alienated a huge swath of the region’s military and tribal leadership. SDF commander in chief Mazloum Abdi has since announced a general amnesty for those who took part in the uprising, with the exception of those the group accuses of having ties to “outside powers.”
Since fighting began, the SDF has alleged that the leaders of the tribal rebellion were cooperating with the Assad regime in preparation to facilitate the latter’s takeover of northern Deir Ezzor.

Credible sources suggest that DEMC Chairman Ahmed al-Khbayl may in fact have harbored such intentions. However, the SDF has since used the charge to refer to most of those who took part in the fighting and as a pretext for further crackdowns. Since Abdi’s call, the SDF has arrested rather than released more tribal leaders thought to have taken part in the fighting.

U.S. officials have reportedly met in recent days with al-Hifl’s relatives living in Qatar in an attempt to reconcile both sides. But the SDF’s large campaign of arrests, combined with the enormous blood spilt during the 11-day uprising, mean that the region will likely never return to the status quo achieved after the Islamic State was mostly defeated in late 2017.
As a result, the SDF will be significantly restrained going forward in its ability to prevent a resurgence of Islamic State cells and prevent the Assad regime, Russia, and Iran from laying claim to Deir Ezzor’s valuable petroleum reserves.

These events put the United States in an impossible situation, for which the stakes could not be higher.

Since its intervention in Syria in late 2014, the United States has made a greater effort to protect northern Deir Ezzor from attacks by outside powers than any other area under SDF control. On Feb. 7, 2018, U.S. airstrikes killed hundreds of Russian Wagner mercenaries who crossed into the area to take over the Conoco gas field, which now hosts one of the largest U.S. bases in the country.

In October 2019, Turkey launched a major campaign to expel the SDF from a 1,200 square kilometer (463 square mile) zone along its border with Syria. In order to avoid clashing with a NATO partner, three days before the assault, the United States agreed to evacuate its forces from front-line positions in Aleppo, Raqqa, and northwest Hasakah provinces and allow Russian soldiers to replace outgoing U.S. troops.

However, Washington refused to relinquish control of oil and gas reserves in Deir Ezzor and southeast Hasakah, as doing so would risk encouraging other parties to the Syrian conflict to take over the area. For the Islamic State and Assad regime in particular, controlling these fields would significantly increase both parties’ access to foreign currency, enabling them to expand and threaten the regional balance of power.

In this environment, the United States became increasingly reliant on the DEMC, whose forces were more effective than the SDF leadership at mobilizing local support. Conscious of their leverage, the DEMC and Deir Ezzor’s tribes began making calls for greater autonomy beginning in 2020.
Al-Khbayl took what many viewed as the first tangible step toward autonomy in May 2023, when he oddly proclaimed himself leader of the Zubayd Emirate, a reference to a seventh-century tribe with branches across Syria, Iraq, Saudi Arabia, and Iran. On May 14, al-Khbayl hosted a gathering of sheikhs from Raqqa, Aleppo, and other distant provinces, who pledged their support for the new tribal entity.

The SDF feared that al-Khbayl would follow up his announcement by expelling the group from Deir Ezzor, and tried to arrest him on July 25, prompting a series of clashes that killed 5 but ended in a DEMC victory. The SDF made their second, successful attempt on Aug. 27, luring al-Khbayl to an alleged meeting with U.S. officials where he was disarmed and taken to a remote desert prison, where he remains.

Members of al-Khbayl’s security detail who managed to evade capture immediately broadcast the news on social media, and within 24 hours, dozens of towns were in the hands of mutinous DEMC fighters and their allies. By Aug. 31, al-Hifl called on the region’s tribes to join the fray, extending fighting for another week.

Though the uprising appears to have been defeated, its impact will be significant. The shared experience of fighting against a mutual enemy will likely push families, clans, and tribes in Deir Ezzor with a past history of disputes to set aside their differences to focus on the common goal of revenge, providing ample fuel for a long-term rebellion.

A case in point is the rebellion’s two most prominent leaders, al-Khbayl and al-Hifl. Al-Khbayl hails from the region’s Bakir clan, rivals of the al-Hifl family since at least 2012, when rebel groups from both sides fought over control of the region’s oil wells in the early years of Syria’s revolution.

Both sides have carried out tit-for-tat assassinations since 2020, while al-Hifl was among the staunchest opponents of al-Khbayl’s efforts to create a Zubayd Emirate. Now, both men and their supporters find themselves on the run, targeted by the SDF.

Al-Khbayl, al-Hifl, and their relatives and followers who cannot be reintegrated into the existing order will likely be courted by the myriad other actors that have already long sought to destabilize this critical region.

Al-Khbayl himself comes from the Bakir clan’s Eid household, whose members joinedthe Islamic State in larger numbers in 2013 than almost any other cohort in Deir Ezzor. The United States and SDF recruited al-Khbayl to lead the DEMC in 2017 in the hopes that he could convince his relatives to abandon the group. With him in prison, they may have less of an incentive to do so.
Despite the many challenges the United States faces elsewhere, Washington must dedicate sufficient focus to Syria and the broader region to ensure that similar divisions don’t emerge between the SDF and other allied Arab factions. Failing to do so will create space for adversaries to undermine Washington’s hard-fought gains.

Clarification, Sept. 15, 2023: This article has been updated to clarify the region in Syria where the United States has increased its protection since the start of its intervention, as well as the circumstances of the U.S. withdrawal from the region in 2019.

Foreign Policy