The Islamic State Attacks the New Syrian Government

For the first time since the fall of the Assad regime, the Islamic State successfully struck the new Syrian government, targeting a security post in the eastern town of Mayadin with a May 18 car bomb attack that left five dead. Intentionally or not, the strike coincided with several other significant developments in the Syria file—it came one day after government forces clashed with an IS cell in Aleppo (the first such sting operation since March), less than a week after President Trump met with President Ahmed al-Sharaa in Riyadh, and subsequent to a U.S. military drawdown in Syria that began in mid-April. Although the local IS presence is nowhere near as strong as it once was, the trend lines point to a persistent threat that cannot be ignored.

IS has continued to operate as a low-level insurgency under the new government that took power in December. As of May 15, it had claimed thirty-three attacks in 2025. On one hand, if this historically low pace continues, it would result in just eighty-nine attacks for the entire year—still a substantial number, of course, but the fewest since the group’s entry into Syria in 2013. On the other hand, a significant spike has been evident since April, when the United States began reducing its troop presence from 2,000 to around 700. It is still too early to know if this is a coincidence, and the current force size is no smaller than the one Washington maintained prior to increasing its deployments throughout the Middle East during the Gaza war. On average, however, claimed IS attacks jumped from around five per month in the first part of the year to fourteen since the withdrawal process began.

The location of these incidents is telling as well—until yesterday, all of them occurred in areas controlled by the U.S.-backed, Kurdish-led Syrian Democratic Forces (SDF), which have been engaged in a promising but still-unfinished process of merging forces with the new government even as the United States draws down. Unsurprisingly, IS appears to be exploiting this situation, in line with its traditional practice of trying to fill or destabilize even the smallest vacuums. The decision to target Mayadin—in government-held territory across the Euphrates River just outside the SDF zone—represents a further escalation, literally and symbolically.

Meanwhile, the new authorities in Damascus continue the fight they have been waging against IS for years—on the battlefield as the breakaway jihadist group Jabhat al-Nusra and then Hayat Tahir al-Sham (HTS) beginning in 2013, as a lawfare approach after establishing an autonomous governing entity in Idlib province in 2017, and on all fronts since toppling the Assad regime last year. On January 11, for example, they foiled an IS plot to stoke sectarian tensions by bombing the Shia shrine of Sayyeda Zainab in the Damascus suburbs. The United States reportedly provided intelligence on this plot, marking an early test of bilateral counterterror cooperation. According to the Ministry of Interior, the suspects also confessed that they were planning to conduct a car bombing attack against a church in Maaloula on New Year’s Day, and to assassinate President Sharaa if he had visited Sayyeda Zainab following that foiled attack.

On February 15, Syrian authorities arrested Abu al-Harith al-Iraqi, a leader in the Islamic State’s “Iraq province,” who helped organize the failed Sayyeda Zainab plot. Previously, he was involved in the assassination of HTS leader Abu Mariya al-Qahtani in April 2024. The Public Security Directorate has also arrested IS cells in Deraa province this year: in al-Naima on February 18 and Sanamein on March 6.

Up until the past few days, the overall situation within government-held territory appeared relatively calm. During the May 17 Aleppo sting, however, one IS operative blew himself up, four others were taken into custody, and three government personnel were killed. More security forces perished in the Mayadin bombing the next day. For its part, the SDF has conducted around thirty arrest raids this year against IS cells in the east—less than in previous years, but still a lot.

All of these trends highlight the fact that even greatly reduced IS operations can still be quite disruptive, especially during Syria’s sensitive transition period. Accordingly, the United States has more reason than ever to avoid fully withdrawing its troops from Syria until the new authorities complete their incorporation of the SDF and get the counter-IS campaign on a more sustainable footing. This means urging the Kurds and Damascus to advance the existing agreement under which the central government is to assume control over all of Deir al-Zour province, the Islamic State’s stronghold. In doing so, they would establish a single administration in the province, thereby preventing IS from exploiting seams between the two areas of control—a vulnerability that likely played a role in yesterday’s successful attack.

The incomplete administrative merger in the northeast also raises the risk that IS will once again try to free the 9,000 imprisoned fighters and thousands more family members and supporters held in SDF detention facilities, some of whom are foreign nationals. Washington could help reduce this risk by continuing to push countries on repatriating their detained citizens. Compounding this problem, last week’s edition of the IS newsletter al-Naba not only called on a new crop of foreign fighters to come to Syria, but also urged HTS fighters who are dissatisfied with the new government’s policies to defect—an oft-heard plea that may now have extra potency given heightened U.S. pressure to expel all such individuals. In short, despite the Islamic State’s current weakness in historical terms, counting the group out would be a mistake, as would making any near-term U.S. policy decisions based on that assumption.

Aaron Zelin is the Gloria and Ken Levy Senior Fellow at The Washington Institute and author of The Age of Political Jihadism: A Study of Hayat Tahrir al-Sham.