On July 4, the Kurdish-dominated Syrian Democratic Forces (SDF), backed by the U.S.-led coalition against the Islamic State (also known as ISIS), broke into the Old City of Raqqa, the jihadist pseudo-state’s de facto Syrian capital. Although fighting in Raqqa will continue to be a bloody grind, when it is over, the battle will be the capstone of what is now a successful, years-long collaboration between the U.S.-led coalition and the SDF.

But the battle against ISIS will not end with the liberation of Raqqa, and neither will the United States’ commitments in Syria. Washington’s approach to fighting ISIS in Syria—and in particular the local Kurdish partner it has chosen—has granted a victory that can last only as long as the United States stays. If one looks beyond Raqqa and the immediate campaign against ISIS, the bigger strategic picture is alarming: the United States has set itself up for an indefinite presence in northeast Syria, in the middle of an unsettled and unfriendly region, with no obvious way to leave.

DIFFICULT ALLIES

The SDF is a Syrian force led by the Kurdish People’s Protection Units (YPG), with which the coalition struck up a tactical partnership against ISIS in 2014. In 2015, the U.S. military helped rebrand the YPG and its smaller, subordinate allies as the “SDF,” apparently in order to put the group in a slightly less controversial package. The YPG is closely linked to the Kurdistan Workers’ Party (PKK), which has waged a decades-long insurgency in neighboring Turkey, Washington’s NATO ally. Further, the YPG and its civilian parallel, the Democratic Union Party (PYD), are seeded throughout with PKK-trained cadres. This has not been lost on Turkey, which sees the PYD-YPG as the PKK’s Syrian affiliate. Since 2014, Ankara has watched the group’s territorial and numerical expansion with alarm, even as it has grappled with a revived PKK insurgency inside Turkey.

The United States has set itself up for an indefinite presence in northeast Syria.

The Obama administration, in a sop to Turkey, insisted it was supplying only the SDF’s uncontroversial Arab elements with weapons. Turkey was not satisfied—both U.S. and Turkish officials understood that these Arab units functioned as auxiliaries to the SDF’s YPG core. Then in May, the Trump administration announced that it would arm the YPG directly in its fight for Raqqa.

Washington’s partnership with the YPG has been a functional one: the United States is in Syria to kill ISIS, and the YPG is excellent at killing ISIS. It is a motivated, coherent, and reliable military force. The alternatives, including those pitched by Turkey in the lead-up to the battle for Raqqa, were not.

But there is little clarity about what the United States will do when the killing is done and what will happen to its partnership with the YPG. During a panel on U.S.-Turkish relations in May, State Department official Jonathan Cohen described Washington’s relationship with the YPG as “temporary, transactional, [and] tactical.” In June, State Department spokesperson Heather Nauert was noncommittal, saying that the United States saw the SDF as the “best force to take back control over Raqqa” while declining to “characterize or get into hypotheticals about the future.” Secretary of Defense Jim Mattis has given mixed signals about whether the United States will continue to arm the YPG after Raqqa.

So far, the United States has made a limited investment in stabilization programming in areas retaken from ISIS by the SDF. Yet U.S. officials have also been emphatic that they will not invest in large-scale reconstruction or nation building—not without a credible political settlement to Syria’s civil war that would turn the regime of President Bashar al-Assad into an acceptable state partner.

That sort of national settlement is not forthcoming, which leaves Washington with unappealing options.

YPG fighters in Raqqa, July 2017. Goran Tomasevic / Reuters

A PATH TO PEACE?

The United States aims to defeat ISIS, not to foster a PYD political project or to take permanent ownership of part of Syria. Yet Washington seemingly cannot declare victory and leave. If it abruptly concludes the battle against ISIS and withdraws from Syria’s northeast, Turkey will attack—or at least that’s what Turkish officials told me. The resulting maelstrom would do grave damage to both Turkey and the YPG. Such chaos would almost certainly give ISIS a chance to recover and reverse the U.S.-led coalition’s gains.

It is possible to imagine an arrangement—a settlement between the Assad regime and the PYD—that could bring the relevant Syrian and regional forces into a rough equilibrium and allow the United States to exit. The PYD, unlike Syria’s revolutionary opposition, has deliberately set its political ambitions below the threshold of regime change. As a result, it and the Assad regime have kept up a tense but functional relationship, and Kurdish and regime-controlled areas have remained institutionally and economically intertwined.

In theory, the Assad regime, PYD, and Turkish positions could be roughly harmonized through a PYD-regime agreement that would preserve some local autonomy in Kurdish areas while ensuring Syria’s territorial integrity and reintroducing enough central state sovereignty to assuage Turkey’s fears. Even if Turkey still objected, the deal could place a joint Syrian-Russian force on the border with Turkey, which Turkey would be unwilling to attack.

In practice, however, this seems unlikely in the near term. The present PYD-regime détente is a long way from a more substantive, complete agreement. Kurdish officials told me that Russian-sponsored negotiations between the two have gone nowhere. They blamed an Assad regime that, even after six years of war, is still maximalist and unreasonable and refuses to recognize what they see as their “rights.” But the PYD is also unwilling to compromise and seems unlikely to make hard choices as long as it is backstopped by the United States.

Inside the U.S. government, moreover, there is little appetite for actively midwifing an agreement between the PYD and Damascus, which is still viewed as toxic and beholden to Iran. In addition, the return of state control to Syria’s northeast would likely be incompatible with the United States’ ongoing counter-ISIS campaign, which would rely on U.S. Special Forces’ freedom to base and operate in the area. And U.S. support for the YPG has helpfully encouraged it to rebuff Iranian overtures, preventing Tehran from establishing a supply route from Iraq to Syria and Lebanon via Syria’s Kurdish northeast.

There is little clarity about what the United States will do when the killing is done.

But the absence of a deal likely means an open-ended, residual U.S. presence in northeast Syria—a de facto partition that will keep Syria and its neighbors in an indefinite limbo. In this scenario, the United States would become the guarantor of a Syrian-Kurdish half state that disrupts and unbalances everything around it. This state would have minimally functional, U.S.-sponsored institutions and services but too little investment to develop and prosper. It would lack open, functional economic links with its neighbors, including Iraqi Kurdistan. To maintain regional peace, Washington would have to continually appeal to the PKK not to attack Turkey, which would in turn be permanently agitated, even if the United States’ presence dissuaded it from intervening in northeast Syria. Yet as one Turkish official warned me: If and when the PKK or its splinter groups carry out a major attack in Turkey, Turkey will respond by bombing YPG targets inside Syria. And eventually, Ankara seems likely to accidentally injure or kill Americans collocated with the PYD or YPG, threatening the U.S.-Turkish alliance and causing American lives to be lost.

A DEAD END

At this point, such a partition may be the best outcome available. But by any objective measure, it is not a good one.

In partnering with the YPG, the United States has won its way into a strategic dead end. It needs to look for an exit. In particular, it should seriously investigate possible coordination with Russia. Kurdish officials told me that Russia is already attempting to lean on the YPG to allow more of the regime back into a northwestern Kurdish enclave outside the United States’ protective umbrella. In the northeast, Russia may be able to help bring the regime and the YPG to a mutually dissatisfying but useful compromise, for which Russia could serve as guarantor.

Winning against ISIS means uprooting the group from its core territory, neutralizing its threat to regional order, disrupting its external operations capability, and then, ideally, leaving in a way that doesn’t explode all of that.

Washington needs to start formulating an exit strategy for northeast Syria. Without one, sustaining victory over ISIS may mean pouring U.S. troops, resources, and credibility into a black hole of regional instability, seemingly forever.