ISIS Exploits Syria’s Chaos as Fighter Numbers Balloon Fivefold

Iraq’s intelligence chief has issued a stark warning that should alarm Western capitals: the Islamic State has quintupled its fighting force in Syria over the past year, exploiting the power vacuum left by tyrant Bashar al-Assad’s collapse to stage what counterterrorism officials describe as a dramatic comeback.Now, with American military and intelligence bandwidth consumed by Operation Epic Fury, the window for ISIS to consolidate that comeback may never be wider.The timing is no accident. The United States and Israel launched surprise airstrikes on multiple sites across Iran on February 28, 2026, killing Supreme Leader Khamenei and triggering a cascading Iranian missile and drone campaign against American bases across the region — from Iraq to the Gulf states. Operation Epic Fury’s stated objectives include preventing Iran from acquiring a nuclear weapon, destroying its missile arsenal, degrading its proxy networks, and annihilating its navy — an all-consuming campaign that critics warn is pulling focus, resources, and regional attention away from the unfinished business of ISIS containment at precisely the wrong moment.Analysts had already sounded the alarm: with international attention focused elsewhere, ISIS would have an ideal opening to strike detention facilities holding thousands of its fighters in northeastern Syria. Those facilities were strained even before the Iran war began. Detention centers near Hasakah and Shaddadi hold approximately 9,000 ISIS fighters and family members across facilities described by defense analysts as acutely vulnerable — a 2022 prison break at Hasakah required two weeks and direct American military intervention to suppress.The Iran war also threatens to unravel the coalition partnerships that have kept ISIS in check. The fatwa issued in 2014 by Iraq’s Grand Ayatollah Sistani introduces an additional destabilizing variable, potentially mobilizing Shiite militias across Iraq and the broader region, the very forces American troops have long coordinated with to hold territory ISIS once controlled. If those militias redirect their guns toward American positions rather than ISIS cells, the consequences for counterterrorism operations could be severe.From an estimated 2,000 fighters just over a year ago, ISIS ranks have swelled to approximately 10,000 militants in Syria, according to Hamid al-Shatri, director of Iraq’s National Intelligence Service. The assessment represents one of the most alarming intelligence revelations about the terror group’s resurgence since its territorial defeat in 2019.Yet the figure could not be independently confirmed by American military sources and conflicts with multiple intelligence estimates. The United Nations Secretary-General’s most recent biannual report placed the combined strength of ISIS in Syria and Iraq at approximately 3,000 fighters as of August 2025, while the International Centre for Counterterrorism put the range at 1,500 to 3,000. United States Central Command last estimated approximately 2,500 active fighters in 2024 — a figure it has not publicly updated since.The discrepancy in estimates reflects the fog of war in Syria’s transitional chaos; however, even conservative assessments acknowledge a troubling trend. In 2024, ISIS carried out at least 660 attacks across Syria — an average of 60 attacks per month, triple the rate recorded in 2023. While overall attack frequency declined after Assad’s fall, the most concerning development in 2025 has been a sharp rise in lethality, with 37 percent of all fatal attacks concentrated in just the final six weeks of the reporting period — evidence that the group is not merely surviving, but sharpening.The resurgence has coincided with an incremental American withdrawal from Syria and Iraq, troop levels falling from 2,000 to below 1,000 since President Trump took office. Independent analysis documented 244 total ISIS attacks in Syria during 2025, with the rise in deadliness concentrated in the final months of the year, particularly after the United States force reductions to approximately 700 personnel in April-May 2025.“The estimates of how many fighters terror groups, such as ISIS, have are always a complex endeavor,” senior director of the Counter Extremism Project, Hans-Jakob Schindler, tells the New York Sun.“One of the key challenges is what is classified as a ‘fighter’. Some governments only estimate the number of individuals that are armed and involved in actual fighting or attacks, while other governments also count all the supporters, including, for example, families.”What is clear, Mr. Schindler underscores, is that “since 2019 ISIS has been rebuilding its structures in Syria and in 2024 and in 2025, for those two years, there is data, it has conducted more terror attacks in Syria than ever before.”Infiltration and Fragmentation Fuel GrowthMr. Shatri’s intelligence assessment points to several disturbing sources feeding the terrorist outfit’s expansion. Many recruits are disaffected fighters who previously aligned with President Ahmed al-Sharaa, the former Islamist militant who now leads Syria’s transitional government after spending years imprisoned in Iraq. These militants, frustrated by Mr. Sharaa’s pivot toward political legitimacy and cooperation with Western powers, have defected to the more radical ISIS banner.The terror group has also absorbed defectors from other militant factions, including Jabhat al-Nusra and Ansar al-Sunna, capitalizing on the broader fragmentation of Syria’s armed opposition. Foreign fighters who once numbered in the thousands under various militant groups now find themselves squeezed by government integration efforts, creating a recruiting pool for ISIS’s more extreme ideology.“ISIS in its propaganda saw the fall of the Assad regime as a significant opportunity,” Mr. Schindler says. “It sees in the current interim administration in Syria less of a mortal enemy and more of an ideological competitor. That difference is significant.”Iraqi officials express deep concern about this growth trajectory. The sectarian dimension particularly troubles Baghdad’s Shia-dominated government, which views Mr. Sharaa’s Sunni-led administration with suspicion despite his public disavowal of jihadist ideology nearly a decade ago.Mr. Sharaa was arrested by American forces in Iraq on May 14, 2005, and imprisoned at Camp Bucca and other detention facilities. He was transferred to Iraqi authorities in April 2010 and released on March 13, 2011, just two days before the outbreak of anti-Assad protests in Syria, due to a lack of evidence under his assumed identity. Mr. Sharaa was detained under Article 4 of Iraq’s terrorism law, yet was released when authorities found no charges against his pseudonym.The Prison Powder KegPerhaps the most immediate danger, however, lies in Syria’s sprawling detention infrastructure, where roughly 9,000 ISIS fighters remain imprisoned in facilities that have become increasingly vulnerable amid the country’s security transition.In January, chaos erupted at the Al-Shaddadi prison in Hasakah province as control transferred from Kurdish-led Syrian Democratic Forces to government troops. Approximately 120 ISIS detainees escaped during the confused handover, though Syrian authorities claim most were recaptured. The prison sat less than two miles from a United States military base, highlighting the risks even in areas with American presence.The Al-Shaddadi incident pales compared to what could occur if larger facilities are compromised. The sprawling Al-Hol and Roj camps hold an additional 38,000 to 42,500 people, primarily women and children linked to ISIS fighters, creating what counterterrorism officials describe as incubation centers for the next generation of militants.“Unfortunately, in the past years, the Kurdish authorities neither had the capabilities nor the capacities to conduct deradicalization programs for male fighters in the prisons in which they were held,” Mr. Schindler says. “This means that, unfortunately, it is highly likely that the absolute majority of the male ISIS fighter population in these prisons remain highly radicalized, loyal to ISIS and have an axe to grind.”The January 2022 assault on Ghwayran prison in Hasakah demonstrated ISIS’s capability and intent. Coordinated car bombs and internal uprisings freed hundreds of fighters during 10 days of intense urban combat that required U.S.-led coalition airstrikes to suppress. That attack killed at least 500 people.United States Central Command has responded to the escalating crisis by launching emergency operations to relocate high-value detainees. In recent weeks, approximately 150 senior ISIS prisoners were transferred from Syrian facilities to Iraq, part of a plan to move up to 7,000 of the most dangerous militants away from vulnerable locations.“The current plan of the US administration to transfer these fighters to prisons in Iraq is a necessary emergency measure,” Mr. Schindler explains. “However, it also risks overloading the Iraqi justice system, as it is doubtful that it would be able to cope with these numbers.”A Strategic ShiftSyria’s new government insists it is committed to defeating ISIS, having joined the United States-led anti-ISIS coalition in November 2025. Yet the scale of the challenge appears overwhelming for security forces still finding their footing.Damascus recently incorporated tens of thousands of recruits and former opposition fighters into its security apparatus, creating an institution of uncertain loyalty and competence. This rapid expansion provides opportunities for ISIS infiltration, as demonstrated by a December attack near Palmyra, where a member of Syria’s own security forces shot and killed two American soldiers and an interpreter.“Since the fall of Assad, the Islamic State has not mounted the widespread insurgency that many had predicted would emerge amid a perceived security vacuum,” research associate at the Terrorism Research & Analysis Consortium, Colette Toubba, who monitors all Islamic State activities in Syria, tells the Sun. “This is largely due to sustained military pressure on the Islamic State, which has pushed the group toward a more decentralized form of power aimed at weakening security rather than causing outright collapse.”Ms. Toubba cautions that “decentralization should not be seen as a weakness, but as a calculated reshaping of strategy for self-preservation, leveraging a war of attrition against security forces within the limits of current operational capabilities.”The American DilemmaWashington faces difficult choices as it reassesses its Syria policy under President Trump’s administration. The United States currently maintains approximately 1,000 troops in Syria, down from 2,000 earlier in 2025, working alongside both the Kurdish-led SDF and Sharaa’s government in an increasingly complicated partnership.The December attack that killed two American soldiers near Palmyra prompted Operation Hawkeye Strike, a massive retaliation that struck 70 ISIS targets with more than 100 precision munitions. Secretary of Defense Pete Hegseth characterized the operation as a declaration of vengeance rather than the beginning of a new war.Tensions between the SDF and Damascus further complicate Washington’s strategy. Recent fighting has killed dozens and displaced thousands, forcing uncomfortable choices about which partner Washington prioritizes. The incomplete integration of Kurdish-controlled areas into Syria’s government structure creates seams that ISIS has historically exploited.Global ImplicationsBeyond Syria’s borders, ISIS has demonstrated its continued global reach with attacks inspired by or directed from its diminished Middle Eastern core. United States Central Command reported that ISIS inspired at least 11 plots or attacks against American targets in 2025 alone, including a New Orleans vehicle attack that killed 14 people in January.“Compared to the physical caliphate until 2019, ISIS in Syria is currently weaker,” Mr. Schindler points out. “However, ISIS globally is stronger than it was until 2019. In the past years, ISIS was able to gain significant ground in West Africa, including in Mali, Niger and Nigeria.”Yet international attention has waned even as the threat metastasizes. Fewer than 40 countries have repatriated their citizens from Syrian detention camps despite years of pressure from humanitarian organizations and security officials.“If a major prison escape were to occur in Syria, neighboring countries such as Iraq would most likely be the first to feel its direct impact,” Ms. Toubba cautions. “On a global level, a successful prison break could lead to a more emboldened Islamic State and psychologically lift the morale of a group that has faced sustained pressure.”The question now is whether Syria’s fragile government, international partners, and regional neighbors can prevent history from repeating itself.“At this point, a successful HTS hinges on continued external support in the form of military power as well as their own domestic ability to organize armed forces on the ground,” Ms. Toubba adds.

ISIS Exploits Syria’s Chaos as Fighter Numbers Balloon Fivefold

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