Iran Update, December 19, 2025

Data Cutoff: 2:00 PM ET

The  Critical Threats Project (CTP) at the American Enterprise Institute and the Institute for the Study of War (ISW) publish the Iran Update, which provides insights into Iranian and Iranian-sponsored activities that undermine regional stability and threaten US forces and interests. CTP-ISW publishes the Iran Update daily.

Click here to see CTP and ISW’s interactive map of assessed control of terrain in Syria, and here to see CTP and ISW’s interactive map of Israeli ground operations. The Syria map is updated daily alongside the static Syria maps in this report. CTP-ISW ended daily maps of Israeli ground operations in February 2025.

Click here to see ISW-CTP's interactive map showing the total strikes in Iran during the Israel-Iran War, as well as an interactive timelapse showing the strikes day-by-day.

The United States struck dozens of ISIS-affiliated targets in Syria on December 19 in direct response to the ISIS-affiliated killing of two US soldiers and a civilian interpreter in Palmyra on December 13.[i] US Defense Secretary Pete Hegseth announced that the US operation aims to eliminate ISIS fighters, infrastructure, and weapons sites.[ii] Unspecified US officials told Western media that US fighter jets, attack helicopters, and rocket artillery struck dozens of suspected ISIS sites across central Syria.[iii] Syrian media reported airstrikes and explosions in desert regions in Homs, eastern Raqqa, and western Deir ez Zor provinces.[iv] CTP-ISW will publish a complete analysis on US strikes in Syria in the December 22, 2025, Iran Update.

The Islamic State’s (IS) recognition of the December 13 attack on US forces in Palmyra may encourage Islamic State in Iraq and al Sham (ISIS)-affiliated or -inspired fighters to attempt to conduct similar insider attacks on US or Syrian forces. A suspected ISIS-aligned Syrian security forces member killed two US servicemembers, a US civilian interpreter, and a Syrian internal security officer in Palmyra, Homs Province, in an insider attack on December 13.[v] IS did not explicitly claim involvement in the attack but praised the attack for targeting the “joint forces” of the United States and Syrian government.[vi] IS’s acknowledgement and praise of the Palmyra attack in a December 18 editorial suggests that IS encouraged and inspired the attack but probably did not have foreknowledge of the operative’s plans.[vii] The attack‘s perpetrator was a recent Syrian internal security forces recruit whom Syrian authorities had flagged before the attack for imminent dismissal over his “extremist” beliefs.[viii]  CTP-ISW assessed on December 15 that recent ISIS calls to monitor US forces and attack Syrian government forces “whenever and wherever possible” may have motivated the perpetrator.[ix]

IS supporters and followers will likely interpret IS’s praise of the Palmyra attack as encouragement to conduct similar “green-on-blue" or insider attacks targeting US or Syrian forces. Many IS supporters online have interpreted IS’s acknowledgement of the Palmyra attack as a claim of responsibility for the attack, according to a BBC Salafi-jihadi expert on December 19.[x] The interpretation that IS claimed the attack may encourage other attacks against US or Syrian forces, regardless of whether IS actually intended its acknowledgement as a claim. IS publishes weekly editorials in its publication, al Naba, to disseminate its ideology and propaganda to IS followers across the world. IS supporters often use these editorials to guide and shape their militant activities, including determining permissible targets and acceptable courses of action. A western Syria-based ISIS-aligned group, Saraya Ansar al Sunnah, interpreted IS’s praise for Palmyra attack as encouragement for individual fighters to conduct further attacks without deference to a “chain of command” as long as the fighters “follow [ISIS’s] methodology.”[xi]

IS’s veneration of the Palmyra attack may signal to IS followers that the organization has adapted its understanding of the permissibility of joining Syrian government forces with the intent to conduct insider attacks. The BBC expert noted that IS supporters have recently debated online if infiltrating Syrian government forces to carry out insider attacks is permissible, particularly given that IS has repeatedly called upon supporters to defect from the “apostate” Syrian government since the fall of the regime.[xii] IS’s approval of the recent insider attack may, however, encourage previously hesitant fighters or supporters to attempt to infiltrate Syrian security or military forces to conduct similar attacks.

Decentralized and isolated ISIS-inspired cells or individuals continue to present a serious threat to US and Syrian forces operating in Syria. That IS acknowledged but did not claim the Palmyra attack suggests that IS was not aware of the attack before it was conducted and that the group has not infiltrated Syrian government forces in any extensive way at this time. The editorial referred to the attackers as those “who have made up their minds,” which suggests that while ISIS believes that the attackers were committed supporters, it also knows that the attackers decided to attack US and Syrian forces independent of formal direction and were not formal members of ISIS.[xiii]  Individuals who are inspired by ISIS can still fulfill ISIS’s goals of driving a wedge between the Global Coalition and Syria by posing a major threat to US and Syrian forces operating in Syria. ISIS-inspired individuals operating individually or within decentralized, disconnected two to three-person cells are much more difficult for friendly forces to detect and dismantle because they are less likely to be connected to or in communication with other ISIS networks. US and Syrian forces have collaborated in recent months to dismantle ISIS cells and detain or kill ISIS leaders across Syria.[xiv]

Iran-backed Iraqi militia Kataib Imam Ali leader Shibl al Zaidi called for Iranian-backed Iraqi militias to disarm and integrate into the Iraqi state in a statement published on X on December 18, which would constitute an initial step towards satisfying the first condition in the 2026 Nation Defense Authorization Act (NDAA).[xv] Iranian-backed Iraqi militias would need to demobilize their extralegal militias and reintegrate them into society, not merely place them under the PMF, to satisfy the first condition of the NDAA’s Iraq section. The NDAA lays out three conditions that the Popular Mobilization Forces (PMF) must meet for Iraq to receive 75% of funds under the Coalition Train and Equip Fund (CTEF): first, extralegal militias operating outside of the control of the Iraqi state must disarm, demobilize, and reintegrate; second, they must answer to the Iraqi prime minister; third, the Iraqi government must hold the militias accountable if the militias break the law. The PMF contains a number of Iranian-backed militias, but other militias operate outside even nominal government control, separate from the PMF.[xvi] Zaidi’s statement is also consistent with an earlier, reported Shia Coordination Framework plan to comply with the reported US demand that the Iraqi federal government disarm six Iranian-backed Iraqi militias, including Kataib Imam Ali and Kataib Hezbollah. The framework is considering a plan to publicly disarm the six militias and integrate them into the PMF.[xvii]  All of the militias except Kataib Hezbollah reportedly agreed to the SCF’s plan, which suggests that Kataib Hezbollah is more ideological than the other militias.[xviii] The reported framework plan and Zaidi’s proposal for disarmament and integration integrates extralegal militias into the PMF but does not satisfy the first condition because it does not demobilize or reintegrate these militias into society.

Key Takeaways

• US Airstrikes in Syria: The United States struck dozens of ISIS-affiliated targets in Syria on December 19 in direct response to the ISIS-affiliated killing of two US soldiers and a civilian interpreter in Palmyra on December 13. CTP-ISW will publish a complete analysis on US strikes in Syria in the December 22, 2025, Iran Update.
• ISIS-aligned Attack in Syria: The Islamic State’s recognition of the December 13 attack on US forces in Palmyra may encourage Islamic State in Iraq and al Sham (ISIS)-affiliated or -inspired fighters to attempt to conduct similar insider attacks on US or Syrian forces.
• Integration of Iranian-backed Iraqi Militias: Iran-backed Iraqi militia Kataib Imam Ali leader Shibl al Zaidi called for Iranian-backed Iraqi militias to disarm and integrate into the Popular Mobilization Forces in a statement published on X on December 18, which would constitute an initial step towards satisfying the first condition in the 2026 National Defense Authorization Act’s Iraq funding. Iranian-backed Iraqi militias would need to demobilize their extralegal militias and reintegrate them into society, not merely place them under the PMF, to satisfy the first condition of the NDAA’s Iraq section.

Iran

The Institute for Science and International Security assessed on December 18 that Iran has placed panels over the anti-drone cage at the Pilot Fuel Enrichment Plant (PFEP) at the Natanz Nuclear Complex in order to explore the rubble at the site discreetly, citing satellite imagery from December 13.[xix] The anti-drone cage seeks to protect the PFEP from drone attacks.[xx] The cage was present at the site before the Israel-Iran War and Israeli projectiles penetrated it during the war. The PFEP’s internal structure, which was also damaged during the Israel-Iran War, is still visible in the satellite imagery.[xxi] International Atomic Energy Agency Director General Rafael Grossi stated on October 18 that the majority of Iran’s enriched uranium stockpile is stored at the Esfahan Nuclear Technology Center and Fordow, and some at Natanz.[xxii]

Iran is facing continued US efforts to drive Iranian oil exports to zero. The United States sanctioned 29 vessels and multiple shipping companies on December 18 for transporting illicit Iranian petroleum and other petroleum products.[xxiii] The US Treasury reported that these vessels carried hundreds of millions of dollars’ worth of Iranian crude oil, among other products.[xxiv] The Trump administration has sanctioned more than 180 vessels involved in Iranian oil transport since January 2025.[xxv] Recent sanctions on December 18 also targeted shipping firms based in the United Arab Emirates, Panama, the Marshall Islands, India, Liberia, and the British Virgin Islands, for their involvement in Iran’s petroleum exports.[xxvi] The United States also sanctioned Egyptian businessman Hatem Elsaid Farid Ibrahim Sakr for facilitating Iranian petroleum exports through UAE-based shipping companies.[xxvii] Sakr’s firms coordinated petroleum shipments linked to Iran’s Ministry of Defense and Armed Forces Logistics (MODAFL)-associated front company Sahara Thunder and facilitated ship-to-ship transfers of Iranian oil exports.[xxviii]

Iraq

See topline section.

Syria

US President Donald Trump signed the National Defense Authorization Act (NDAA) and repealed the 2019 Caesar Syria Civilian Protection Act on December 18.[xxix] The Caesar Act was the most stringent layer of US sanctions imposed on Syria and imposed secondary sanctions that targeted anyone who provided financial support to the Syrian government.[xxx] President Trump is required to submit a report to Congress within 90 days of the NDAA’s passage that confirms that the Syrian transitional government is meeting eight key US security demands.[xxxi] These demands require the Syrian government to continue to cooperate with the United States on counter-ISIS efforts, ensure the safety of religious and ethnic minorities and hold those accused of recent human rights abuses responsible, and refrain from taking “unilateral, unprovoked military action” against its neighbors.[xxxii]

The United Kingdom sanctioned two Syrian army commanders and three Turkish-backed armed factions on December 19 for committing human rights abuses during the Syrian coastal massacres in early March.[xxxiii] All of these entities are currently integrated into the Syrian army. The United Kingdom sanctioned 62nd Division Commander Brigadier General Mohammad al Jassem (Abu Amsha) and 76th Division Commander Brigadier General Saif al Din Boulad (Sayf Abu Bakr) for their role in the “suspected atrocities” during the Syrian Civil War and the coastal violence in March 2025.[xxxiv] The United Kingdom also sanctioned their factions, the Sultan Suleiman Shah Division and Hamza Division, respectively, and a third Turkish-backed faction, the Sultan Murad Division, for human rights abuses.[xxxv] Abu Amsha, Sayf Abu Bakr, and their factions committed atrocities against Syrian minorities during the civil war and have continued to commit such atrocities in the months since the fall of the regime.[xxxvi] The United States sanctioned Abu Amsha and Sayf Abu Bakr in 2023 for committing serious human rights abuses against Kurds.[xxxvii] The European Union also levied sanctions against them and their factions in May 2025 for their involvement in the coastal massacres.[xxxviii] CTP-ISW continues to assess that Shara’s promotion of militants who have committed human rights abuses to prominent defense positions will threaten Syria’s long-term stability.[xxxix] The United Kingdom did not sanction the Sultan Murad Division‘s former civil war commander, Brigadier General Fahim Issa. Issa currently holds a prominent role in the Defense Ministry as the defense minister’s assistant for the northern region.[xl]

Arabian Peninsula

An unspecified actor launched a drone on December 19 targeting United Arab Emirates (UAE)-backed Southern Transition Council forces near al Abr, Hadramawt Governorate, and injured an STC fighter.[xli] No actor has claimed responsibility for the attack at the time of this writing. STC spokesperson Mohammad al Naqeeb characterized the drone attack as a terrorist attack similar to those that al Qaeda in the Arabian Peninsula (AQAP), the Houthis, and the Muslim Brotherhood (Islah Party) conduct in Yemen.[xlii]

Palestinian Territories and Lebanon

Lebanese and Israeli military and civilian representatives held a ceasefire monitoring committee meeting on December 19 amid warnings that Israel could escalate its operations in Lebanon in the coming weeks.[xliii] The officials reportedly discussed the Lebanese Armed Forces (LAF) disarmament progress, efforts to secure the return of residents to their homes near the Israel-Lebanon border, and economic cooperation.[xliv] A source familiar with the details told Axios on December 18 that the meeting aimed at preventing the resumption of conflict in Lebanon.[xlv] A source familiar with the discussions told Reuters on December 19 that meeting “addressed disputes” over how the LAF should deploy in southern Lebanon and disarm Hezbollah.[xlvi] The next ceasefire monitoring committee is reportedly scheduled for January 7, 2026.[xlvii] These meetings come amid Israeli warnings that Israel could expand its operations in coming weeks.[xlviii] Israel reportedly warned the Lebanese government recently that Israel’s participation in ceasefire monitoring committee meetings does not restrict the IDF from continuing to strike Hezbollah targets in Lebanon.[xlix] Israel conducted at least 14 airstrikes targeting several Hezbollah military sites across Lebanon on December 18, for example.[l]

Unspecified Israeli intelligence officials told Israeli media on December 17 that Israel’s objective in Lebanon is to degrade Hezbollah to the point at which the LAF is militarily stronger than Hezbollah.[li] Unspecified Israeli intelligence sources told Israeli media on December 17 that Hezbollah is currently stronger than the LAF but that it will be a “change in [Israel’s] favor” once the LAF becomes the stronger actor.[lii] The sources said that Israel will need to continue fighting Hezbollah “at all costs” to achieve this stated objective.[liii] An unspecified senior IDF official similarly told Israeli media on November 24 that the IDF must degrade Hezbollah to a point where the LAF is militarily stronger than Hezbollah.[liv]