The United States-led attack to punish the Syrian regime two weeks ago triggered a change in the American approach to Syria unrelated to the chemical attacks. The combined bombing campaign by the U.S., France, and the United Kingdom had narrow objectives of degrading Syrian chemical weapons capabilities and deterring the regime from repeated use—nothing approaching previously suspected plans to ground the Syrian air force and leadership decapitation. But the circumstances that preceded the attack did revitalize discussions within the administration to refocus attention on Iran, a week after U.S. President Donald Trump announced in Ohio that he would leave Syria “very soon.”

The Syrian camp’s post-strike mood was celebratory. A senior official in the regional alliance supporting Syrian President Bashar al-Assad told Reuters that the attack was too limited if that was the end of it—an assessment that most observers seem to share. Two days later, Assad was also reportedly in a “good mood” and Syrian media labeled the attack the “tripartite aggression,” named after the botched British, French, and Israeli attack against Egypt in 1956.

In one sense, the pro-Assad camp is right. If anything, the action that was supposed to deter the Syrian regime only signaled that the U.S., despite support from two other nations, was itself deterred from acting meaningfully against Damascus. The fact that the three Western powers refrained from targeting any installations linked to Iran inside Syria also signaled a lack of appetite to escalate beyond a slap on the wrist.

In another sense, the attack, despite its weakness, demonstrated Washington’s willingness to escalate against the Syrian regime. Compared to the one last year, the attack is larger and involved two more countries. More importantly, the U.S. made it clear it was willing to pursue more lethal options—such as grounding the Syrian air force—but it restrained itself, regardless of the specific reasons for that decision, leaving different options if a similar scenario plays out. In other words, for the Assad regime, the scale and scope of a third round of attacks would be unpredictable. That the regime would use chemical weapons again is still possible, but it is much less likely under the current circumstances and after the latest attack against it.

The Iran Factor

However, a more critical element is missing from the debate since the episode unfolded. Even though the role of Iran featured little in public discussions that followed the attack on April 13, a major part of Donald Trump’s eight-minute speech, otherwise focused on chemical weapons, spelled out Washington’s idea to prevent Tehran from benefiting from the territorial demise of the Islamic State in the region.

To understand how Iran might stand to lose from the U.S. reaction to the chemical attack, consider how the administration’s Syria policy has evolved since January, when Trump signed onto a comprehensive and ambitious plan with four main objectives. The objectives included a political settlement in Syria, overseeing the lasting defeat of jihadis, depriving Iran from a land corridor linking Iraq and Syria, and ensuring Syria is free of chemical weapons.

That plan was essentially withdrawn after Trump’s remarks in Ohio on March 29, when he said the U.S. would be leaving Syria “very soon.” The comments signaled that the U.S. would abandon the plan the president had previously approved, as if he suddenly developed a distaste to a dish he had just ordered. With the air strikes, the U.S. mission remains the same, but deliberations inside the White House since to rejigger the Syria strategy to suit the Trump’s public commitments. This broad policy debate became even more intensive since the chemical attack was reported, which coincided with the appointment of John Bolton, an Iran hawk.

The remarks in Ohio exposed an inherent flaw in the otherwise promising strategy on Syria, namely that doing what it takes to ensure the lasting demise of groups such as the Islamic State may not necessarily align with Trump’s political “instincts,” and so it would risk being thrown out when tested. The president has consistently said the U.S. will not continue to waste blood and treasure to secure a “troubled place” like the Middle East, as he put it during his speech two weeks ago; he does not want Syria to be his Iraq, an indefinite mission that might cost American lives; and he does not want the U.S. to engage in “nation building” overseas. Any long-term plan has to account for Trump’s stated principles if it is to survive election rallies.

To address this, a number of benchmarks have to be met in an ongoing review of the plan laid out in January. As analyst Michael Weiss revealed in the Daily Beast on Monday, Trump requested four areas of improvement in the existing plan: the U.S. presence should not be a replay of the occupation of Iraq, it should not be permanent, the U.S. should not spend money on rebuilding eastern Syria, and the plan should ensure that extremists do not reconstitute themselves and present a threat to the U.S. homeland. In other words, the plan for Syria should be limited to its original minimal objectives but involve a phase-out clause.

The magic formula that could reconcile Trump’s political instincts with the views of his generals and advisers could be discerned in his speech two weeks ago. He reaffirmed American commitment to the mission against the Islamic State in eastern Syria, a mission that he said would help to protect the American people. Trump also emphasized U.S. commitment to enabling allies in the region to become more engaged in securing their own neighborhood. “It’s a troubled place. We will try to make it better, but it is a troubled place,” he said.

Critically, Trump framed the increased engagement of Arab countries in the context of countering Iran and filling the void that would be created if and when the U.S. eventually leaves. “Increased engagement from our friends, including Saudi Arabia, the United Arab Emirates, Qatar, Egypt, and others, can ensure that Iran does not profit from the eradication of ISIS,” he said. Trump went on to add, “As other nations step up their contributions, we look forward to the day when we can bring our warriors home.”

The last sentence is crucial. While Trump signals that American troops will leave Syria, he conditions departure on the ability of allies in the region to fill the vacuum. Few disagree that the hasty withdrawal from Iraq in 2011 caused a power vacuum that led to the rise of the Islamic State in 2014. Trump has repeatedly blamed former president Barack Obama and secretary of state Hillary Clinton for withdrawing in 2011 and creating the power vacuum.

Increased Regional Involvement

According to a plan proposed by National Security Adviser John Bolton and new Secretary of State Mike Pompeo, Arab allies would become involved on the ground through their own expeditionary forces to replace the 2,000 U.S. troops currently deployed in eastern and northern Syria. The Arab involvement would also involve financial sponsorship for the security project in Syria.

In principle, the plan has already had quiet approval for more than a year. Soon after Trump’s inauguration, according to the foreign minister of one of the Arab allies he refers to, Trump asked Gulf leaders to step up their financial support for the mission in eastern Syria. The Gulf leaders agreed in principle, but reconvened joint teams to “study” the plan.

Earlier this year, the Saudis sent a delegation to Turkey to discuss the matter. Officials in Ankara told the Saudis they would support the effort, through Turkey’s borders, but not while the Syrian Democratic Forces were dominated by the Kurdish YPG, the People’s Protection Units that Turkey accuses of being an affiliate of the Turkish PKK. Saudi officials passed on the message to the Trump administration. Washington has since sought to bridge differences between it and Turkey, but it is unclear whether the two efforts are related.

Also, a Gulf official told me last year that the Saudi-led Islamic Military Counter-Terrorism Coalition had proposed sending 40,000 troops from various countries with the aim of fighting extremists in eastern Syria. The proposal was snubbed by the U.S., according to the official. After Trump’s recent remarks, the Saudi foreign minister also publicly declared his country’s willingness to send troops to Syria. In fact, the U.A.E. already has troops operating inside Syria alongside American, French, and British special forces, according to civilian sources involved in the anti-Islamic State effort in the country.

Despite moves behind the scenes, the push by Trump in this regard was brought up more frequently in recent months, and he mentioned it during his remarks as he announced the Syria attack two weeks ago. “We have asked our partners to take greater responsibility for securing their home region, including contributing large amounts of money for the resources, equipment, and all of the anti-ISIS effort,” he said.

Again, on Tuesday, during a press conference with French President Emmanuel Macron, Trump reiterated the message but in a provocative manner that angered the Arab allies. He demanded that those “wealthy” Arab countries should pay and send troops to Syria instead of the U.S., and that those regimes would fall within a week had it not been for American protection. After the remarks, the Saudi foreign minister, deflected blame to Qatar, saying the survival of the regime in Doha depends on American support, and so Doha should be paying for the American troops in Syria.

Notwithstanding the provocative remarks, Trump still referred to a commitment to counter Iran in Syria, during his presser with Macron. He said: “We will have a strong blockage to the Mediterranean, which to me is very important because if we don’t you have Iran going right to the Mediterranean. Not gonna have that.”

Inconceivable Withdrawal

As jihadis lose ground in both Iraq and Syria, Iran stands to lose from a sustained American presence that aims to strengthen allies as part of the phase-out process. The U.S.-backed forces control one-third of Syria—an area the size of West Virginia—in a critical border region near Iraq. Eastern Syria is a predominantly Sunni tribal region, with a sizable Kurdish population that is skeptical of an Iranian or Assad regime presence. For now, the regime and its Iranian allies are locked out of this region, where most of Syria’s hydrocarbon, water, and vital agricultural produce are located.

Beyond Syria, the U.S. has coordinated with regional allies to counter growing Iranian dominance. In Iraq, for instance, the U.S. under this administration successfully pushed Saudi Arabia to engage in a systematic outreach with the Shia of Iraq, in a bid to address fears that often draw people toward Iran as a defender of Shia. This resulted in unprecedented cross-sectarian gestures, such as the historic visit of Muqtada al-Sadr to Riyadh last summer.

Iran is becoming a top priority for American allies, especially in the wake of the containment of jihadi groups. Israel has stepped up its bombing campaigns in recent months inside Syria, typically targeting Iranian assets. The American presence in eastern Syria, even if it were not framed in the language of countering Iran, is necessary to ensure that the Islamic State remains dead in that region and near the borders. The Islamic State is already recovering in much of Iraq and Syria. Iran is also seen as a political and sectarian factor for the rise of jihadi groups in West Asia.

All these factors make it inconceivable, at least in the eyes of generals involved closely in the battle against jihadis, to withdraw from Syria in the foreseeable future. When Trump said he would do just that, the deliberations that followed seem to have persuaded him that an alternative was needed. He has since moderated his stance and demanded instead that regional allies step up to the plate if they needed the U.S. to stay. The exit plan he laid out during his speech would involve American allies filling the void.

The chemical attack, a mere week after Trump signaled he would leave Syria, led the president to reverse his position and articulate a plan bespoke for his political inclinations that brought him to power. This reversal, if incorporated into strategy reviews Trump’s advisers are preparing, will no doubt prove to be a setback for Iran, more than Assad.