The Islamic State is actively rebuilding and poised to exploit security gaps as the United States prepares to complete its withdrawal from Iraq by the end of September, a regional security expert has warned. Dr. Omar Mohammed, a counterterrorism expert and researcher with the George Washington University Program on Extremism, stated that the terror group is "waiting actively in the gaps, as it historically always has."
The U.S. troop presence in Iraq is set to conclude by Sept. 30, marking an end to a 23-year deployment. Mohammed cautioned that the period following the U.S. withdrawal could become the most dangerous in Iraq since ISIS seized Mosul in 2014. He highlighted that the question is not whether U.S. forces will leave, but what the consequences of their departure will be.
Mohammed explained that the dynamic between Iran-backed militias and ISIS is interdependent, with each group justifying the existence of the other. "The militias claim the ISIS threat in order to keep their weapons, while ISIS recruits from the grievances that the militias create," he said. This cyclical relationship, he warned, mirrors the conditions that led to Mosul's fall in 2014, when the city was caught between a sectarian security apparatus and the insurgency it fueled.
After ISIS captured Mosul, the group established underground networks through assassinations, extortion, and infiltration, seizing U.S.-made weapons before declaring a caliphate. Mohammed, through his blog "Mosul Eye," documented life under ISIS rule and provided intelligence to U.S. forces. Although Iraqi forces, with coalition backing, recaptured Mosul in 2017, ISIS has continued to operate in parts of Iraq and Syria.
Recent estimates suggest a significant increase in ISIS fighters in Syria, with numbers potentially growing from around 2,000 to as many as 10,000 since the Syrian government's collapse in 2024, according to Iraqi intelligence estimates cited by Mohammed. He also noted that the Popular Mobilization Forces (PMF), an umbrella organization integrated into Iraqi security forces, has not been disbanded. This group, estimated to have about 238,000 members and substantial government funding, includes factions with close ties to Iran that operate outside Baghdad's direct control.
Baghdad is currently attempting to bring these armed factions, including Kataib Hezbollah and Asaib Ahl al-Haq, under state authority. Mohammed characterized Sept. 30 as a dual deadline, referring to both the U.S. withdrawal and the domestic disarmament push. He emphasized that "the militias and ISIS are not separate stories; they are deeply interdependent. Both forces thrive in the unstable spaces the central state cannot hold."
The U.S. withdrawal follows a 2024 agreement that outlined the end of the mission in Iraq by 2025 while continuing support for anti-ISIS operations in Syria through September 2026. Mohammed warned against complacency, stating, "Mosul did not fall in 2014 because ISIS was strong. It fell because everything that would have detected its strength—presence, attention, honest reporting from the ground—had been withdrawn in the years before, while the world's eyes were elsewhere."
Meanwhile, the recent meeting between Iraqi Prime Minister Ali al-Zaidi and U.S. officials, which led to the announcement of the troop withdrawal, drew condemnation from Iran. Ali Akbar Velayati, an adviser to Iran's Supreme Leader, called al-Zaidi's trip "regrettable" and claimed it damaged Iraq's dignity. Mohammed indicated that Iran's influence in Iraq is crucial, especially after U.S. strikes weakened its proxy network. He suggested that Iran's primary concern is not a resurgence of ISIS, but rather a potential irrelevance in a stable Iraq where militias are disarmed and U.S. forces depart on Baghdad's terms.
"What happens across the wider region after September will not be decided by anyone's stated intentions or diplomatic promises," Mohammed concluded. He warned that whether ISIS grows large enough to threaten Iran or remains a tool for it will be a defining question of the year following the U.S. withdrawal.