Nine months after the longtime dictator Bashar al-Assad was toppled by a rebel offensive, Syria faces a litany of new challenges. The country, which is now being led by the militant group Hayat Tahrir al-Sham (HTS), is contending with recurring violent sectarian clashes, successive Israeli strikes into Syrian territory, and internal disputes within the new government. Adding to the tumult is a resurgence of one of Syria’s most enduring challenges: the Islamic State, also known as ISIS.

Since the Assad regime was toppled in 2024, ISIS has waged a terror campaign throughout Syria, targeting the new Syrian government, as well as Christian, Shiite, and Kurdish minorities. At its apogee, in 2014, ISIS held roughly a third of the country. Although the group no longer controls any territory in Syria, and its numbers have dwindled from roughly 100,000 fighters to 2,500 fighters today, the group is taking advantage of Syria’s post-Assad chaos to rebuild and reconstitute, presenting fresh obstacles to the country’s long-sought stability.

The group’s targeting capabilities are proving more frequent, precise, and sophisticated than ever, targeting sites well beyond ISIS’s traditional spheres of operation. In June, for example, a suicide bomber linked to ISIS attacked a Greek Orthodox church in Damascus, killing 25 and injuring 63. Two months later, the group launched more than two dozen attacks across northeastern Syria, relying on a combination of guerrilla tactics, including small arms fire, ambushes, assassinations, and improvised explosive devices targeting military checkpoints and government vehicles. Last year, ISIS took responsibility for 294 attacks in Syria, up from 121 in 2023; estimates by the United Nations and human rights groups are even higher. 

Such attacks pose a blatant challenge to the new administration’s attempts to stabilize the country. Syria’s already fragile security situation is characterized by frequent clashes between Sunni, Alawite, and Druze communities. As the frequency of terrorist attacks increases, the new Syrian government risks squandering its political legitimacy by failing to protect the country’s minorities. The Syrian population, meanwhile, faces a real possibility of a large-scale terrorist resurgence. 

This situation will grow more dangerous still if the Trump administration follows through on its plan, announced in April, to begin withdrawing the approximately 2,000 U.S. troops stationed in the country. Since 2014, the United States has been the linchpin of the Global Coalition to Defeat ISIS, an international counterterrorism group that has worked with local security forces to degrade ISIS. Without Washington’s active involvement, the coalition’s remaining 88 members will struggle to keep ISIS at bay or to adequately support local actors such as the Syrian Democratic Forces (SDF), a mostly Kurdish militia that had recently reached an agreement to merge with the state.

ISIS sees an opportunity in a divided Syria. Its leaders seek to exploit the country’s sectarian and ideological divisions to recruit new fighters and rebuild their caliphate. Through its attacks, ISIS hopes to demonstrate that the current Syrian government is unable or unwilling to protect the population, especially minorities. A recent report from the UN Monitoring Team concluded that ISIS “will continue to project an external threat . . . if divisions in the country allow a permissive space from where they can plan and execute attacks.”

Indeed, ISIS was especially busy last spring. In March, in the aftermath of violence between Sunni and Alawite communities in the port city of Latakia, ISIS conducted a string of attacks against the SDF. Then in May, the group launched another barrage of attacks following clashes south of Damascus, between the new administration’s security forces and Sunni and Druze communities. That same month, just a week after U.S. President Donald Trump met in Riyadh with Syria’s new president, the former jihadist Ahmed al-Shara, ISIS launched a series of bombings and ambushes across Syria and Iraq. The group also took credit for planting an explosive device that struck a “vehicle of the apostate regime” in southern Syria, resulting in at least seven Syrian army casualties and marking the first recorded attack on Syrian government forces since Assad’s fall. A week later, another bomb attack conducted by ISIS in southern Syria targeted fighters from the Free Syrian Army, a U.S.-backed militia. Notably, all these attacks transpired deep in government-held territory.

This surge in violence has been accompanied by a surge in ISIS propaganda undermining Shara and HTS. In its weekly online newsletter, which reaches and inspires jihadists across the globe, the group routinely maligns Shara and the new government and calls for soldiers in the Syrian military to defect. ISIS propagandists call Shara “Jewlani,” in reference to a conspiracy that the Syrian president, formerly known as Abu Mohammad al-Jolani, is an Israeli Mossad agent installed to initiate regime change inside Syria in favor of Israel. The group has also labeled HTS as kuffar (Arabic for “nonbelievers”) and accused it of being a puppet of the United States and Israel. Since HTS and Shara came to power, Israel has repeatedly carried out strikes and ground incursions into Syria, sowing the very chaos on which ISIS strives.

How things develop in Syria will depend, at least in part, on how committed Washington remains to continuing its fight against ISIS. After a decade and a half of extreme violence perpetrated by myriad actors, both state and nonstate, Syria faces a long road toward stability under the best of circumstances. Any U.S. withdrawal would create space for ISIS and other terrorist organizations to step up their attacks, further destabilizing the country, sowing divisions among its rival factions, and even opening the door for Iran-backed Shiite extremists, including Hezbollah. If the government in Damascus falls, or if it is unable to unify the country’s minority communities, Syria will plunge back into civil war.

Rather than prematurely depart a fragmented Syria, the United States and its partners in the Global Coalition should make long-term investments in the country’s security. The U.S.-led mission has significantly degraded ISIS over the preceding decade, and U.S. forces have effectively collaborated with the SDF and other local actors on counterterrorism measures. Although ISIS remains largely defeated, Syria’s postregime transition has created an opening for the group’s return. The United States should withdraw from Syria only when Syrian forces can defend the country against ISIS and other terrorist groups. That moment has not yet arrived.