As the assault on Raqqa, the Islamic State’s (ISIS, ISIS, or Daesh) Syrian “capital” gathers steam, one hopes that the national security team of the Trump administration is working to devise a Syria policy that can do lasting damage to Islamist extremism in Syria and beyond. Routing a few thousand armed criminals from Raqqa—ideally without an accompanying humanitarian catastrophe—is vital. It should have been done with military professionals long before the expiration of the Obama administration. In and of itself, however, the capture of Raqqa will not be a decisive blow. It must be coupled with a Syria policy promoting political transition from state failure to political legitimacy.

The first—and perhaps fatal—obstacle to a policy that would aim to make Syria inhospitable to Islamist extremists is an American officialdom that may see the undertaking as too hard to do. The United States Department of Defense (DoD) and Central Command (CENTCOM) oversee a Kurdish-led ground campaign against ISIS that minimizes American casualties in pursuit of a military victory.

Victory, however, can be sealed only by means of an executable stabilization plan for liberated areas. Yet working with the Syrian opposition to try to heed the harsh post-combat stabilization lessons learned from Iraq in 2003 and Libya in 2011 is dismissed by some in the administration as nation-building. Indeed, some American officials invoke the name “Ahmad Chalabi” as a reason not to work with the Syrian opposition on post-conflict stabilization, equating the Iraqi confidence man with (for example) former Syrian Prime Minister Riad al-Hijab: someone who has never tried to impose himself on foreign sponsors.

Just as it is content to use militiamen to storm a complex urban environment, so DoD is prepared for liberated eastern Syria to be administered by some patchwork of “locals,” instead of a coalition-supported Syrian administration. During a May 19, 2017 press conference, Special Envoy Brett McGurk alluded to local people arising spontaneously in areas from which ISIS was routed. But Secretary of Defense James Mattis identified the real bottom line in the following exchange:

Q: Okay, can you address the expectations from the American troop presence in Syria? I mean, should Americans expect that they will be there in some numbers for years to come?

SEC. MATTIS: I’m not willing to say that right now. I’d — I’m not willing to sign up for that. That’s not our intent. We’re there to drive ISIS to its knees. And, as Mr. McGurk pointed out, there’s got to be a political solution to the larger issues there. It’s not going to be U.S. troops at the point of a gun making that happen.

DoD, therefore, in 2017, defines its mission as defeating ISIS militarily in Syria. In Iraq, in 2003, it saw mission accomplishment as the taking of Baghdad. Secretary Mattis assigns the post-ISIS “larger issues” to a “political solution” that he and his colleagues declined to define, beyond Mr. McGurk’s assertion that there ought not be a restoration of the Assad regime in liberated eastern Syria. But with Russia and Iran seemingly intent on restoring Assad rule to all of Syria, who is to prevent it? Who will stop the conditions that gave rise to Islamist extremism in Syria in the first place from being fully reestablished?

No doubt President Obama left his successor cornered in Syria. The combination of not wishing to offend Iran with respect to Tehran’s valued client (Assad) in the western part of the country, and relying on a Kurdish-dominated militia to fight ISIS in the east, produced the worst of all worlds for defenseless Syrian civilians and for American partners in the region. The beneficiaries of that policy combination were Assad, his external enablers (Iran and Russia), and an al-Qaeda affiliate seeking to dominate the armed Syrian opposition. President Trump accomplished a partial breakthrough for American interests by responding militarily to an Assad regime chemical attack on civilians and to an attempt by Iranian-led, pro-regime militia to overrun an American-supported, Syrian rebel base in the southern part of the country.

As important as these gestures are to restoring American credibility, they are not sufficient. With the passive acquiescence of the Obama administration, Moscow and Tehran succeeded in stabilizing the position of a man whose murderous, civilian-centric tactics made him a premier recruiter for al-Qaeda and ISIS: Bashar al-Assad. The forthcoming liberation of eastern Syria offers an opportunity for a genuine Syrian alternative to Assad to emerge: an alternative that can jump-start an otherwise stillborn political transition discussion in Geneva. That alternative would require the support of the United States and its regional partners. The alternative cannot, in an overwhelmingly Arab area, be a Kurdish-dominated militia. It cannot be a disparate, fragmented, undefended collection of local administrations.

To leave post-combat stabilization in eastern Syria to chance is to risk setting the stage for one of two unacceptable outcomes: the emergence of ISIS 2.0; or the restoration of a regime whose behavior recruits globally for Islamist extremism. It is not enough to assign post-combat stabilization in eastern Syria to a notional “political solution” that one hopes will somehow take shape in a manner consistent with the interests of the United States and its allies and partners in the region and beyond.

Ideally ISIS will be erased in eastern Syria. Yet the victory must be sealed. How to seal it—how to support the rise of an alternative to the terrorist-abetting Assad—should have been determined long, long ago. Urgent consultations with American allies and partners—including the Syrian opposition—are essential if lessons supposedly learned from Iraq and Libya are to be applied to areas liberated from ISIS. The stakes are too high to be left to militiamen or to chance.

Frederic C. Hof is director of the Atlantic Council’s Rafik Hariri Center for the Middle East. 

Image: Syrian Democratic Forces (SDF) fighters on their way to Raqqa, Syria June 6, 2017. REUTERS/Rodi Said TPX IMAGES OF THE DAY