ISIS Redux: The Central Syria Insurgency in September 2021

October 1, 2021
Gregory Waters  —  Research Analyst

Following is the September 2021 installment of “ISIS Redux: The Central Syria Insurgency,” a monthly chronicle of attacks by the terrorist group ISIS in central Syria. Previous editions of ISIS Redux can be viewed through the following links: August, July, June, May, April, March, February, and January 2021; and December, November, October, September, August, July, June, May, and April 2020. A full background and analysis of ISIS’s resurgence in Syria, including its methodology, can also be explored herehere and here.

ISIS militants carried out at least 36 confirmed attacks in September, killing at least 56 pro-Assad regime fighters and seven civilians, while wounding at least 22 others and kidnapping three civilians in the Homs, Deir Ez Zor, Raqqa, and Aleppo governorates. ISIS activity surged across the entire central Syrian Badia in September following a five-month drop in attacks. More than half of September’s attacks were carried out in the Homs governorate, where ISIS cells appear to have launched a small offensive across four different areas in an attempt to pre-empt impending Russian, Iranian, and regime operations in the governorate. Additionally, an ISIS cell successfully infiltrated the outskirts of Damascus city and conducted a high profile sabotage mission, destroying the main pipeline carrying gas to two major power plants (Deir Ali and Tishreen) and plunging the capital into darkness for several hours.

Not only did high quality* attacks climb in September, but ISIS fighters significantly changed their attack style compared with previous months. ISIS cells had transitioned to less aggressive attacks beginning in April, relying mostly on mines and IEDs to harass regime patrols and defend their core territories. August saw this policy begin to change as less than half of confirmed ISIS attacks used mines or IEDs.

As this author stated in August, this policy change hinted at an impending surge in ISIS activity, as an increase in small arms attacks implied increased operational capabilities and freedom of movement. In September, only 11 attacks were confirmed to have been conducted with mines or IEDs while at least 21 attacks involved small arms. This significant shift in attack type, combined with the surge in activity across the entire Badia, indicates that ISIS cells have likely finished the relocation and reestablishment process made necessary by large regime operations that began at the outset of 2021.

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ISIS increased its targeting of civilians, specifically shepherds, killing seven and kidnapping three in eight different attacks in Homs, Hama, and Raqqa. Both attack lethality and the number of total casualties increased significantly in September compared to the previous five months. ISIS cells also returned to eastern Hama this month after a near complete absence in the province for more than two months. For the fourth month in a row, ISIS succeeded in killing at least one pro-regime commander, and for the first time since March, successfully raided a regime position for supplies.

Confirmed attacks in September in Homs (21) surged after dropping to a 16-month low in August. The high rate of activity in Homs overshadowed increased attacks in both Raqqa (4) and Hama (6), the latter of which had seen no ISIS activity at all in August. Attacks in Deir Ez Zor (4) remained largely steady compared with last month while confirmed activity in Aleppo (0) continued to fluctuate around the zero-to-one attacks per months level. ISIS cells conducted a high quality attack in Raqqa for the third month in a row and Deir Ez Zor for the second month in a row, but the bulk of high quality attacks occurred in Homs (5).

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September ISIS activity in Homs reached a level not seen since this author began tracking central Syria attacks in January 2019. Fighting was concentrated on four fronts: the mountains north of Palmyra, the south and west sides of the ISIS-controlled Wadi Doubayat, and Humaymah, and the countryside south and west of Kawm. While the high rate of attacks during the third week of the month captured the most attention, ISIS cells had been ramping up activity here since the beginning of September. According to local regime security forces, this renewed activity began with ISIS cells laying fresh mines and IEDs around the Palmyra area.

Whereas ISIS only carried out two attacks in Homs in August, its fighters conducted at least four attacks in the first week of September. These attacks, mostly mines or IEDs, were focused around the mountains north of Palmyra and in the desert south of the city, stretching to the U.S.-controlled Tanf zone on the Syria-Jordan-Iraq border.

The second week of September again saw four attacks, though severity increased slightly and a new front was opened. On September 9, a Russian Lieutenant Colonel was killed when his vehicle hit a mine in the governorate’s southeast, possibly in the region north of Tanf. That same day, a family of civilians was killed when their vehicle hit a newly laid mine in the farmlands west of Palmyra. Three days later, militants attacked a regime outpost northeast of Sukhnah—the edge of the strategic Kawm front that the two sides have been fighting over for several months. The next day another regime soldier was reportedly killed in the Tanf region.

ISIS fully launched a mini offensive in the third week of September when it conducted at least nine recorded attacks. However, the actual number of attacks is likely higher, as explained below. On September 17, pro-regime National Defense Forces (NDF) soldiers based in the Badia reported that ISIS cells in the Doubayat Gas Field area south of Sukhnah had been clashing with Iranian-backed Afghan foreign fighters. Those same sources reported additional details two days later, claiming that at least 25 Afghan foreign fighters had been killed over the previous week in continuous, intense clashes with ISIS.

Similarly, on September 24, NDF sources reported that ISIS had been engaged in steady skirmishes for five days with another group of Afghan foreign fighters and members of the Russian-backed 5th Corps in the remote town of Humaymah, along the Homs-Deir Ez Zor border in southeast Homs. The reports went on to say that at least seven Syrian soldiers had been killed in the clashes before the Russian Wagner private military company arrived and helped push back the attackers. The Doubayat and Humaymah battles were listed as two and three attacks, respectively, and dated based on when they were reported to have begun and ended. In reality, it is very likely that clashes occurred more regularly.

Beyond these two fronts, ISIS cells continued to conduct steady attacks around the southern edge of the Kawm front. On September 17, two members of the pro-regime Liwa al-Quds militia were killed in the Sukhnah area, and on September 19, a third regime soldier was reported killed, while ISIS separately succeeded in raiding a regime food warehouse 11 miles west of Kawm.

Lastly, ISIS pre-empted planned regime patrols north of Palmyra with several days of intense battles around the Mustadira and ‘Ubayrah mountains. On September 18, ISIS ambushed a convoy of Liwa al-Quds fighters approaching the ‘Ubayrah mountains, killing five and wounding 14. “Intense” clashes continued the following day, according to local NDF fighters, with additional soldiers killed and wounded. On September 21, Wagner forces supported by Syrian units reportedly “cleared” Jabal Mustadira—just south of ‘Ubayrah—after a short fight, although no ISIS fighters were reported killed or captured.

Fighting in these northern fronts calmed down during the last nine days of the month, although two soldiers were reported killed in the Palmyra and Sukhnah areas on September 22 and 23 respectively. The aforementioned Humaymah battled ended on September 25.

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Map of ISIS attacks in Homs in September 2021 (highlighted dots). Not included in the map is one attack that occurred on September 9 in east Homs, likely in the southern part of the governorate.

Deir Ez Zor

Confirmed ISIS activity in Deir Ez Zor dropped slightly in September. Of the four confirmed attacks, only two were significant. On September 22, a regime colonel was killed in an ambush, along with three of his men, while leading reinforcements to assist embattled forces in Humaymah. The ambush reportedly occurred near the T2 Pumping Station, which sits on the road connecting Humaymah with Abu Kamal at the Iraqi border. Two days later, loyalist forces claimed they repelled an attempt by ISIS to cut the Palmyra-Deir Ez Zor highway just west of the town of Kabbabj. Readers of this series will recognize this town as the site of one of the biggest ambushes against regime, which took place in late 2020.


Between June 25 and September 3, ISIS only conducted one confirmed attack in the Hama governorate, where a mine hit on a regime militia likely carried out by a cell based in northeast Homs. Multiple regime security members interviewed by this author in July and August were adamant that the main ISIS cells had withdrawn from the governorate at the time.

However, on September 4, ISIS militants conducted a small arms attack on a regime checkpoint south of the strategic Ithriya crossroads. Four more mine or IED attacks occurred over the rest of the month (three hitting civilians and one, on September 27, killing a soldier on patrol) and, based on their locations, seem to show the cell moving southwest from Ithriyah along the highway towards Salamiyah. It therefore appears that at least one cell re-infiltrated eastern Hama in September.


Confirmed ISIS activity in south Raqqa increased in September, possibly due to the arrival of cells previously based in east Hama. All four attacks in Raqqa targeted shepherds in the Maadan countryside in the southeast of the governorate. On September 4, the body of a young shepherd kidnapped the day before and executed, was found in the countryside. Two days later, three shepherds were kidnapped in the same area. On September 20, another shepherd was executed and some of his sheep killed—the rest were likely stolen. This time, security forces were close enough to respond to the attack, driving the ISIS fighters away. Four days later a cell attempted a similar attack nearby late in the evening, killing 120 sheep before security forces again intervened and the attackers withdrew.

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Map of ISIS attacks in Raqqa in September 2021 (highlighted dots).

Regime Operations

Anti-ISIS operations have not changed significantly after reaching what appears to be their geographic limit several months ago. Since then, security forces have focused on securing their new outposts and conducting patrols. This stability in territorial movement has enabled ISIS cells to re-establish themselves in the mountains of northeast Homs and in the deserts of southeast Homs and southwest Deir Ez Zor.

In Hama and Raqqa, regime forces continued to prioritize protecting locals from ISIS attacks while herding their flocks or farming. The Russian-backed 5th Corps also continued its monthly sweeping operation across eastern Hama and southern Raqqa. Meanwhile, the Russian Wagner PMC continues to be deployed across the region as a stopgap force assisting regime and Iranian forces in the Palmyra and Humaymah regions.

Looking Ahead

ISIS reminded everyone this month of the degree to which it has embedded itself in Syria. The wave of complex, drawn-out battles across the Badia combined with the significant infiltration operation into the Damascus area demonstrates the limits of Russian, Iranian, and Syrian regime efforts to counter the group. To be clear, throughout most of 2021, these allied forces did successfully turn what appeared to be, at the end of 2020, an unstoppable wave of ISIS expansion. But there are limits to what brute force and unsophisticated air support can achieve against an embedded and dispersed rural insurgency.

Those limits may have been reached in recent months when the regime and its allies were no longer able to push into the remaining core ISIS territories in the mountains and deserts of the Badia. ISIS used this pause to regroup and rebuild its lines of communication and logistics. September showed a return to the mix of offensive and defensive operations that dominated ISIS strategy here in the second half of 2020. However, it is unlikely that October will see the same level of violence.

More importantly, the decision to dedicate resources to infiltrate and attack crucial energy infrastructure serves as a new milestone for the insurgency. It may mark the beginning of a smaller scale version of the anti-infrastructure offensive the group carried out in Iraq in June and July of this year that saw scores of power pylons destroyed. Alternatively, ISIS in the Badia may focus more on carrying out fewer but more impactful attacks like the one in Damascus.

Other than the attack in Damascus, ISIS claimed no attacks in central Syria for the second month in a row. The group clearly understands the importance outsiders place on its claims for assessing the group’s strength. ISIS has thus made a conscious decision not to draw the attention of the West to its activities in a region that it sees as the bedrock of its eventual return to power in both Syria and Iraq. September’s attacks should therefore serve as a reminder to those wishing to write off ISIS as a defeated force that the group not only remains but has long-term plans to return.

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Map of locatable ISIS attacks (highlighted dots) in September 2021. This map does not include four attacks which did not have specific locations attributed to them; one “Hama countryside” attack, one “Homs countryside” attack, and two “Deir Ez Zor countryside” attacks. To view an interactive version of this map, please click here.


*High quality attacks are defined as attacks behind frontlines, those that result in seized positions, target regime officers, involve coordinated attacks on multiple positions, fake checkpoints, ambushes on military convoys, or attacks on checkpoints that kill at least three soldiers or lead to POWs.

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