Biden’s Warning to Iran and Its Proxies: Implications of the Syria Strike

In the early hours of February 26, U.S. aircraft bombed an east Syrian base used by Iran-backed Iraqi militias. The strike was a response to the February 15 rocket attack on Erbil International Airport, where the U.S.-led coalition has a major base. Underlining the U.S. determination that Iran’s militia proxies undertook the Erbil attack, the Syria strike followed a U.S. complaint and warning sent to the Iranian government via backchannels. Although exact damage assessment is yet to be revealed, this first use of force by President Biden shows that the United States will use the military instrument to restore deterrence (however temporarily) even as it prepares for nuclear talks with Tehran.

The Abu Kamal Strike

The U.S. air operation in Abu Kamal, a Syrian district on the Iraqi border, showed very precise and restrained use of force. The area targeted is the most important zone of concentration for Iran-backed Iraqi militias in Syria, which has been struck repeatedly by Israel and (separately) the United States since 2018. This area—particularly the Iranian-built site called the Imam Ali Base Complex—has been used to store Iranian rockets, drones, and the military industrial equipment needed to make and maintain them.

Seven satellite-guided 500-pound bombs were dropped, while other planned munitions releases were cancelled for operational reasons. A dedicated militia border crossing leading to Imam Ali Base was struck, as were six weapons facilities inside the base, though the lack of large, visible secondary explosions suggests that the sites did not contain munitions, fuel, or explosives at the time. Iraqi militia channels reported one member killed and several wounded. As stated in numerous on-the-record and background comments by administration officials, the strike was intended to be “defensive,” “proportional,” and “de-escalatory.”

Striking a target in Syria in response to a provocation in Iraq was deliberate and not without precedent. Secretary of Defense Lloyd Austin stated he was “confident” that the U.S. operation hit “the same Shia militias that carried out the strikes” in Erbil. According to various sources, the groups struck were the U.S.-designated terrorist militia Kataib Hezbollah and its close cousin, Kataib Sayyid al-Shuhada. The determination that these Iranian-backed groups were the perpetrators was made on the basis of strong evidence uncovered through investigation after the Erbil attack. The benefit of striking in Syria was to lessen the risk of political blowback in Iraq, where militias might respond to domestic attacks by once again trying to overrun the U.S. embassy, collapse the government, or evict foreign advisors.

Fallout from the Strike

Observers on both the hawkish and dovish sides of the U.S. foreign policy community greeted the strike with muted praise, while regional observers expressed relief given their doubts that Biden would use force against the Iran Threat Network so early. Moreover, the administration took care to ensure that this first use of force did not rebound negatively from a legal or collateral damage perspective.

One of the strike’s key messages is that judicious use of the military instrument remains in the U.S. toolkit under the new Democratic administration. After militias brazenly attacked the capital of the Kurdistan Region of Iraq, endangering U.S. persons and killing one Iraqi and one Filipino, there was no apparent hesitation at the presidential level about whether to respond, only discussion about where and when. The use of force was preceded by a call between Biden and Iraqi prime minister Mustafa al-Kadhimi on February 23, indicating deep U.S. commitment to safeguarding Baghdad’s ongoing stabilization efforts. Indeed, Washington worked very closely with the Iraqi government and the Kurdistan Regional Government throughout this mini-crisis.

The strike also showed that many of the challenges faced by the Trump administration in Iran, Iraq, and Syria have carried over, so there is no realistic choice other than to draw on some of the same tools in response. Syria will remain a likely venue for future retaliatory strikes on Iran’s proxies—and possibly for attacks in the other direction as well, including militia strikes on U.S. bases.

Policy Implications

The administration intended to send an unambiguous message to Iran and its proxies that attacks on U.S. persons will not be tolerated. In the Erbil incident, militias fired two dozen rockets into a U.S. base nestled close to a densely populated city. Multiple U.S. fatalities and perhaps dozens of civilian fatalities were narrowly avoided. By extension, the prospect of U.S.-Iran nuclear negotiations survived a near-death experience as well. Such talks remain a top priority for the administration, and the use of force was a corrective to keep that prospect alive. Yet the Biden team has publicly stated and quietly signaled to Iran through backchannels that attacks on Americans must stop if negotiations on sanctions relief and related matters are to succeed.

Once the shock of Biden’s early use of force wears off, Iran and its proxies will likely come to further realizations: that the U.S. strike was purposefully restrained (this time at least), that it was directed outside Iraq, and that it was only triggered by a direct, large-scale attack on a U.S. base. This suggests that militias will test Biden’s boundaries again in the coming weeks—most likely by targeting Saudi Arabia from Iraq (as they did using drones on January 23 and January 26), and perhaps via less-intense probing attacks on or near U.S. facilities. Indeed, militias that do not have large numbers of personnel in Syria—such as Asaib Ahl al-Haq, which led propaganda coverage of the Erbil attack—may now be emboldened, perhaps believing they are safe from U.S. strikes conducted across the border instead of at home. Similarly, Tehran may feel comfortable “fighting to the last Arab” if it believes U.S. retaliation will only fall on militias rather than against the Islamic Revolutionary Guard Corps (IRGC) or Iranian territory. And if the United States becomes more heavily invested in direct talks, Tehran may conclude that it can further test Washington’s willingness to sacrifice that process.

For now, the administration should focus on tidying up the legal end of this confrontation by designating Kataib Sayyid al-Shuhada and its leader, Abu Ala al-Walai, as terrorist entities, reflecting their role in the Erbil attack and their longstanding ties with other designated entities such as the IRGC Qods Force and Kataib Hezbollah. The United States should also press its partners—especially Britain and the European Union—to mirror the designation of Kataib Hezbollah. Although this episode was a superb example of U.S.-Iraqi security cooperation, communication with international partners could be improved.

On the military front, the United States should temporarily provide intensified air defenses in the Erbil area in case of further attacks there. It should also be prepared for militias to direct their revenge against the closest target—the Kadhimi government—and ready itself to answer any major provocations against this partner with further warnings to Iran and strikes against proxies. Finally, it should thicken up intelligence coverage of the Nineveh Plains area, both to protect Erbil and to ensure that neither militias nor the Islamic State spring any nasty surprises when Pope Francis visits the area on March 7.

Michael Knights, the Bernstein Fellow with The Washington Institute, has profiled Iran-backed militias and politicians in Iraq since 2003.