U.S. and partner forces killed or captured nearly 25 Islamic State operatives in Syria in the days following a large-scale U.S.-led strike on Dec. 19, according to a Syria’s security environment remains shaped by former jihadist networks that were never fully demobilized after the war. The country’s transitional leadership, including President Ahmed al-Sharaa, emerged from armed Islamist factions that relied heavily on foreign fighters and militias, according to regional security assessments. While those groups are not synonymous with ISIS, experts say the incomplete dismantling of extremist networks has left gaps that ISIS cells continue to exploit.

"ISIS today doesn’t need a caliphate to be dangerous," Bill Roggio told Fox News Digital. "We’ve always been quick to declare terrorist organizations defeated and insignificant, and that couldn’t be further from the truth."

Roggio said the group has adapted rather than disappeared, shifting away from holding territory toward smaller, more covert cells capable of carrying out lethal attacks. He pointed to ongoing ISIS activity not only in Syria and Iraq, but also in Afghanistan and other regions, citing United Nations reporting that estimates roughly 2,000 ISIS fighters remain active in Afghanistan alone.

"That’s not what a defeated group looks like," Roggio said, noting that ISIS continues to recruit, indoctrinate and inspire attacks even without the visibility it once had.

One of the most sensitive vulnerabilities remains the network of detention facilities in northeastern Syria holding thousands of ISIS terrorists and supporters. Those prisons are guarded primarily by Kurdish-led forces backed by a small U.S. military presence, estimated at roughly 1,000 troops, according to Reuters.

U.S. and coalition officials have repeatedly warned that any major disruption to prison security could allow hardened ISIS operatives to escape and reconstitute networks across Syria and beyond. Kurdish officials have also raised concerns about funding shortages, manpower strain and pressure from rival militias operating nearby.

While U.S. officials have not publicly linked the recent strikes to prison-related threats, analysts say the broader environment of fragmented control increases the risk of coordinated attacks, insider assistance or prison unrest.

The danger is not theoretical. ISIS has previously staged mass prison break operations in Syria and Iraq, including a 2022 assault on the al-Sinaa prison in Hasakah that required days of fighting to contain.

The U.S. strikes also come amid continued instability inside Syria, where multiple armed actors operate with overlapping authority. Analysts note that clashes among militias, sectarian violence and unresolved command structures have weakened overall security and diverted attention from counterterrorism efforts.

"These are signals, not spikes," Roggio said. "ISIS operates across regions, adapting to pressure and exploiting weak governance wherever it finds it."

The renewed U.S. military action raises difficult questions for policymakers about how long the current containment strategy can hold.

While U.S. officials say the Dec. 19 strikes delivered a significant blow to ISIS infrastructure, they have also acknowledged that counterterrorism operations alone cannot eliminate the underlying conditions that allow the group to persist.

"Just because we want to declare the war against terror over doesn’t mean it’s over," Roggio said. "The enemy gets a vote."