Now that the Islamic State has been territorially defeated in its last significant safe haven in the Middle Euphrates Valley in Deir ez-Zor, attention is turning to securing and stabilizing the area. Drawing on extensive communications with local residents in Deir ez-Zor, U.S. officials involved in coalition efforts, SDF commanders, local citizen journalists, and tribal figures among other sources, this article argues there is a high risk of a significant jihadi revival in the area.
Removing the Islamic State from Deir ez-Zor was always going to be a significant challenge, especially because unlike in Iraq, the United States has had to work exclusively with a non-state actor to liberate, secure, and stabilize territory that had been seized from the Islamic State. By the summer of 2017, that force, the Kurdish-dominated Syrian Democratic Forces (SDF), had expelled the Islamic State from much of northeastern Syria and reached its second center in Raqqa. (1) At that point, the SDF had already become stretched to the limit. (a) The Kurdish YPG, or the People's Protection Units, was operating farther away from its strongholds in the north and thus relying heavily on U.S. firepower to drive the group out of the city. (2)
The situation for the SDF was further complicated as the U.S.-led coalition advanced south to the governorate of Deir ez-Zor, the final major battleground against the Islamic State in Iraq and Syria, because it is the only province in eastern Syria that has no indigenous Kurdish communities. The SDF's limited capabilities--in terms of manpower, training and local knowledge--allowed jihadis to survive and melt into the local population. (3) It also caused the battle to drag on for twice as long as the fight in Mosul, providing the Islamic State with more time to prepare for a future insurgency and terrorism campaign by establishing sleeper cells. (4)
The slow campaign against the Islamic State in northeastern Syria by the U.S.-backed coalition also allowed the Assad regime to get a 'head start' in the race to 'liberate' Deir ez-Zor, with pro-Assad forces back in control of the west side of the Euphrates River by late 2017. As this article will outline, the return of regime control has provided fertile conditions for the Islamic State and the al-Qa-'ida-linked Hayat Tahrir al-Sham to tap into local Sunni anger to rebuild their operations in the region. (b)
Finally, the announced pull-out of U.S. troops from Syria (5) will only make it more difficult to secure and stabilize the area because U.S. disengagement risks the entire region falling back under Assad control. It risks creating even more fertile conditions for a jihadi revival.
The Islamic State's Last Territorial Stand
On September 5, 2017, the Assad regime backed by relentless Russian firepower broke a siege that the Islamic State had imposed around Deir ez-Zor's provincial capital for nearly three years. (6) Forces loyal to the government had maintained control of several neighborhoods inside the city, against all odds. At its zenith in 2014-2015, the Islamic State had been in control of the rest of the province to the south, west, and east of the garrison, in addition to Hasakah and Raqqa to its north. Despite being equipped back then with an army of suicide bombers, the group had failed to drive out the regime forces from this critical part of eastern Syria. This had resulted in a stalemate, the regime unable to break the siege despite repeated attempts.
The siege was broken after Damascus was able to turn its full attention to the province, with intensive air cover from Russia and heavy ground support from Iranian-backed militias. (7) The regime and its allies benefited from reduced fighting elsewhere in the country due to de-escalation agreements brokered by Russia, Iran, and Turkey, which enabled it to allocate resources to the battle in Deir ez-Zor Governorate. (8) Four days after the Russian-backed forces broke the siege, the U.S.-backed SDF hastily launched a campaign to clear the Islamic State from Deir ez-Zor, even though the battle in Raqqa was still ongoing. (9)
After the siege was lifted in the town of Deir ez-Zor, the Assad regime's campaign there was concluded in just two months. (10) Given the long, grinding campaign by the SDF on the eastern side of the Euphrates in the region, it is yet to be fully explained why forces loyal to Assad were able to take back control of the western side so quickly, especially since all of the Deir ez-Zor Governorate's urban centers except one are situated on that side. (11)
As forces loyal to Assad advanced on the western side, the Islamic State seemingly did little fighting and just melted away. (12) By contrast, it has now been fighting against the SDF in the rest of Deir ez-Zor for 17 months, a period nearly twice as long as its battle to keep control of Mosul in Iraq and more than four times longer than the fight to hang onto Raqqa.
The U.S-backed SDF launched its operation in Deir ez-Zor on September 9, 2017, advancing from southern Hasakah near the Syrian-Iraqi borders along a dead tributary of the Euphrates known as the Khabour River. (13) The forces headed west toward the Euphrates River and then south into the small town of Hajin and the border town of Abu Kamal, two miles from the border with Iraq. (c)
The SDF's operation initially made quick gains, despite its rushed start before the end of the Raqqa campaign. (14) Around mid-November 2017, the SDF liberated all the areas situated along the Khabour tributary and started to move south along the Euphrates River. By then, the first in a series of military pauses had slowed progress. (15) Even so, by late 2017, the Islamic State appeared to be crumbling in the face of the U.S.-backed forces and had lost control of the west side of the river to the Assad regime.
As the Islamic State withdrew from the western side of the river, the group concentrated its war effort on the SDF side. (16) Its numbers there were swelled not only by this but also Islamic State fighters who had moved to the eastern side of the Middle Euphrates River Valley from other areas the Islamic State had previously controlled in Iraq and northern Syria. (17) With most of the villages east of the river emptied of its original residents, the areas the SDF were trying to liberate had become a sanctuary for Islamic State militants and their families. (18) As the SDF advanced slowly south in the period up to late 2017 and in the period that followed, Islamic State fighters moved their family southward from one village to another. (19)
In early 2018, the SDF resumed fighting and took control of the so-called Shaytat towns--three villages named after the Shaytat tribe and the victims four years previously of the single worst massacre carried out by the Islamic State in...