After almost a year of negotiations to resolve differences over the war in Syria, the United States and Turkey are no closer to reaching agreement on a proposed “safe zone” along the Turkish-Syrian border. In a speech over the weekend, President Recep Tayyip Erdogan, again, announced his intention to invade northeastern Syria: “We entered Afrin, Jarablus, and Al-Bab. Now we will enter the east of the Euphrates. We shared this (information) with Russia and the U.S.” Erdogan’s threat came just a few days after Amb. James Jeffrey visited Ankara for inconclusive talks about Syria’s northeast, and on the eve of a follow-on visit by U.S. military delegation to discuss the same topic.

The risk of a unilateral Turkish intervention is high and any such move would make conditions for the American and allied militias in Syria more difficult. However, for Ankara, the threat is a simple reiteration of policy, and makes strategic sense, given the very real fact that Turkey is willing to risk the lives of American military personnel because of deeply held grievances about U.S. policy in Syria and the concurrent empowerment of the Syrian Kurds.

In talks with the United States about the northeast, Ankara has pushed a maximalist position and demanded full control over a 32 kilometer-deep stretch of territory, spanning from the Euphrates River to the Syrian-Turkish-Iraqi border. The United States has sought to manage Ankara’s expectations, pushing against the notion of a Turkish-run zone, in favor of a U.S.-administered area, where Ankara would have a small, limited presence and Kurdish militants would be withdrawn from a strip of territory five to 14 kilometers deep. This fundamental disagreement stems from a serious divergence in threat perceptions and interests in Syria — related to Ankara’s concerns about the empowerment of Kurdish militias, on the one hand, and Washington’s concerns about ensuring Islamic State’s defeat, on the other. This core divide has vexed the two NATO allies since late 2014 and, despite close to half a decade of talks, neither side can offer the other a compromise that satisfies each country’s core national interests.

This problem is critical to understanding the recent decline in U.S.-Turkish relations. The debate in Washington about “who lost Turkey” focuses on U.S. support for the Syrian Kurds in the war against ISIL and how, narrowly, a monomaniacal American focus on the defeat of Islamic State is to blame for Ankara’s recent embrace of Russia and threats to invade northeastern Syria. Some argue that to save the relationship it is important to grapple with the failed assumptions about U.S. policy in Syria and to reassess America’s hesitance to use direct military force to help topple Syrian president Bashar al Assad. This interpretation of the story fails to grapple with the core, quixotic problem driving the recent rupture in U.S.-Turkish relations and why it is so difficult to reconcile the two countries’ policies in Syria. It also explains why how the safe zone talks have proved so challenging and are likely to fail. At the core of the U.S.-Turkish divergence is the very real face that each side has fundamentally different conceptions of regional security.

The root cause of the problem is that both America and Turkey see the other as a fundamentally destabilizing actor in the Middle East. While both sides remain interested in talking, given that the two sides are NATO members, they are not interested in compromise because each side has decided that its own national security interests in Syria are more important than the interests of the opposing party. President Erdogan’s recent reiteration of Turkey’s long-standing threat to launch a unilateral military offensive into Syria to crush Kurdish militants will bring this problem to a head.

Trump’s Safe Zone and Erdogan’s Disingenuous Offer

The U.S.-Turkish talks about a safe zone in Syria’s northeast began in December 2018 in a rather odd way: In a telephone call, President Donald Trump defied his advisors and agreed to a maximalist demand put forward by his counterpart, President Recep Tayyip Erdogan. In what was certainly an opening bid, designed to elicit an American counter proposal, similar to Turkey’s current demands to burden-share inside a Turkish-operated buffer zone along the border, the Turkish president offered to take over the U.S. mission in northern Syria, and replace the American and European troops now based in Syria’s northeast with Turkish forces. These troops, then, would finish the then-ongoing territorial war against ISIL and, presumably, assume responsibility for ensuring that ISIL elements hiding in Syria’s rural areas remain pacified and unable to reclaim territory lost. In retrospect, it appears that the Turkish president was trying to position Ankara for a U.S. counter of opening talks about how to introduce Turkish forces and remove Kurdish elements from the border, following the U.S.-led defeat of Islamic State’s physical caliphate.

However, rather than stick to a script of warning Ankara that any such move would have negative consequences for the bilateral relationship, Trump jumped at Erdogan’s offer. The American president’s eagerness to withdraw stems from his disdain of open-ended American conflict in the Middle East and, in Syria, a long-standing desire to get regional actors to pay for the building of “safe zones” for refugees because he believes that the U.S. military presence enables adversaries and allies to free ride on the back of U.S. military power. A Turkish offer to assume the costs of a war, therefore, would have allowed Trump to withdraw troops and pass the torch on the responsibility for combat operations in at least one conflict in the Middle East. The Turkish offer was never genuine, but was instead designed to pressure the United States to begin to break ties with the Syrian Democratic Forces (SDF), a Kurdish-led militia that has spearheaded the fight against Islamic State. The SDF is led by the Peoples’ Protection Units (YPG), which is the Syrian branch of the Kurdistan Workers’ Party (PKK). The PKK is an insurgent group, active militarily in Turkey since 1984, and listed as a terrorist group in the United States and Europe (along with Turkey). Thus, even while Trump had responded positively to Turkey’s offer, the rash decision took Erdogan by surprise, prompting a call to carefully manage the withdrawal of U.S. forces from Syria with Turkey, even if that meant slowing down the exit Ankara is eager to get underway.

The delay in implementation, ultimately, turned out not to be in Turkey’s interests. This allowed for members of Trump’s administration to convince him to reverse his order, in favor of remaining in Syria together with French and British forces. However, the Turkey challenge remained, giving way to a series of protracted discussions between Ankara and Washington that have, to date, made no reported progress. In recent weeks, Turkey has sought to increase pressure on the United States, threatening to unilaterally invade unless Washington acquiesces to Ankara’s demands to establish a 32 kilometer-deep safe zone.

The Manbij Model: Turkey’s Pressure Campaign

Turkey’s demands are similar to the difficult, and still ongoing, talks about Manbij, a Syrian town west of the Euphrates River under de-facto SDF control. In June 2018, after months of Turkish threats to invade, the United States and Ankara reached agreement on the so-called Manbij Roadmap, a three-phase plan to try and resolve differences over the city’s governance. In the first phase, Washington and Ankara would conduct “independent, joint patrols,” followed by joint patrols, and then efforts to reform governing institutions inside the city by vetting men and women for links to the PKK — and taking action to remove any members that are deemed too close to the Kurdish group. Beyond the mechanics of the arrangement, neither the United States nor Turkey ever agreed on the meaning of key elements of the text, giving way to differing interpretations about the Manbij Roadmap’s implementation and intent.

For this reason, the document has failed to ameliorate tensions and, in fact, has worsened them because Ankara has used its interpretation to accuse the United States as acting in bad faith and dismissing its security concerns. These tensions and vast divergences over Manbij underscore just how fraught and difficult it is to reconcile American and Turkish aims in northern Syria. The inability to reach agreement over a safe zone east of the Euphrates River could prompt Ankara to try and increase pressure on the United States through the use of military force. Any such operation would entail considerable risks, not the least of which because Turkey would be operating without American acquiescence, raising the possibility (no matter how remote) of Ankara’s inadvertent killing of a U.S. solider. To prevent any such operation, the United States has, quite literally, used soldiers deployed in Syria as a “human deterrent,” and ordered elements of the military to drive with American flags flying over vehicles along the border. Further, in a handful of towns and cities along the border, the U.S. has established Observation Posts, ostensibly to protect Turkey from border threat, but in reality designed to decrease the risk of any unilateral Turkish operation.

The challenge, of course, is that the United States has a small number of troops in Syria and, stemming from Trump’s December call with Erdogan, has reduced the number from around 2,000 to 1,000 soldiers without replacing any U.S. personnel with European reinforcements. This means that the United States is spread thin in Syria, and its forces are not able to be everywhere all the time. Thus, even though there are observation posts in most of the border towns with Turkey, they are not always manned. Turkey, quite obviously, has the means to monitor U.S. troop movements in Syria, giving Ankara the opportunity to stage an incursion if the political leadership make the determination that the reward outweighs the risk.

Risk Versus Reward: Ankara’s Options in Syria

The dead-end negotiations with the United States over Syria’s northeast may now incentivize a small, limited Turkish operation along parts of the border. In fact, such a move would make some strategic sense for Ankara, so long as the intent was to quickly take control of Tel Abyad, a border town and, perhaps, Kobane, the city that resisted the ISIL siege and led to the U.S.-SDF entente in 2015. After seizing these two towns, Ankara could then go back to the United States and demand further concessions, pointing to its holding of territory, and signaling that it would be prepared to take more if its demands are not met. This operation would not be as expansive as Turkish officials have threatened, but would be disruptive enough to put pressure on Washington, and even risk SDF retaliation along the entirety of the border. Any such escalation, of course, could prompt Turkish retaliatory strikes, setting in motion an escalatory cycle that could threaten U.S. forces and put pressure on Ankara to increase its military presence.

This destabilizing tit-for-tat is what Ankara is betting on, although it is unclear if Turkey has a serious plan to actually manage a hostile population in perpetuity. However, if Ankara concludes that it really has run out of options, and concurrently makes the strategic decision to devalue relations with Washington further, there is an inherent logic to taking bold action, in line with what the Turkish government has long made clear is an option it is willing to pursue. Faced with this potential incursion, the options for the United States are not good, and its options to prevent any such movement are extremely limited.

Before any Turkish operation, Erdogan is likely to try and schedule a call with Trump, where he would essentially issue an ultimatum to the United States. Given their purported affection for one another, it is unclear how this call would go, given Trump’s suppressed determination to remove troops from Syria. Ankara could also determine that Trump’s relationship with Erdogan is worth preserving and a unilateral intervention would undermine a relationship Ankara has invested in and depends on for protection from Congressionally mandated sanctions linked to Turkey’s purchase of a Russian-made S-400 missile system.

However, even though Ankara has prioritized its relationship with Trump, the leader-to-leader dynamic has not prevented Turkey from using the threat of military intervention to try and elicit concessions from the United States, as was the case in Manbij before the finalization of the Roadmap. Thus, if Ankara chooses to intervene, the reality is that the U.S. military would not be in a position to stop it, and would instead be left to reiterating what is U.S. policy: The U.S. military will only act in self-defense. Of course, as Ankara’s presence in Syria increases, the risks of accidentally killing Americans increases, raising the risks Erdogan would have to consider. For the United States, the dynamics are different. Beyond the narrow risk to U.S. personnel, the greater challenge stems from the inevitable SDF reprisals. Any such move risks igniting a conflict where U.S. forces are mere bystanders, albeit ones that are wedged between two hostile parties. Faced with this unenviable position, Trump could choose to leave Syria, or he could sour on Erdogan and issue his own threat to the Turkish leader that the United States would defend itself from the escalating violence, raising the specter of an unintended U.S.-Turkish clash in Syria.

This uncertainty and the inability to reach agreement with Turkey over the parameters of a safe zone are linked to the very real fact that the two sides are not willing to compromise over core national security interests in Syria, even if that lack of compromise ensures relations will continue to deteriorate. The United States, in choosing to intervene in the conflict against Islamic State alongside a Kurdish militia, made a choice to elevate the threat of transnational terrorism and regional stability over its relationship with Turkey. Ankara has, for its part, never accepted that its embrace of the Syrian opposition and its concurrent open border policy helped to radicalize the opposition, exacerbating critical problems with the non-Kurdish elements of the anti-Assad opposition. The fact is that, despite years of efforts, billions of dollars in aid per year and a near endless supply of small arms, the core of the Turkish-backed opposition was fractured, militarily incapable, and deeply penetrated by extremist groups linked to al-Qaeda.

These factors meant that the U.S. military would never be able to work alongside Ankara’s preferred groups because they were too weak and too radical. The opposition dynamics, in turn, underscore the divergence in threat perceptions driving each country’s current Syria policy. The United States remains committed to defeating transnational Sunni jihadist groups through the use of military force, while Ankara has adopted the same policy, albeit in response to PKK-allied groups along its border. These two blocks of insurgents — Kurdish nationalist and Sunni jihadist — came into conflict in Syria, leaving both sides to choose how to intervene and who not to support, outside of the relatively narrow grouping of Syrian Arab militias that both sides could get behind in other parts of the country. But for a serious U.S. military effort (without direct support from the regime or its backers) to defeat Islamic State, built around a light military footprint, the reality is that the SDF was the only real option to build a coherent battle plan around.

Faced with such uncertainty, it is important to think about what it is that the United States can now achieve in Syria, now that the Islamic State has been territorially defeated. A Turkish incursion would make a lot of strategic sense for Ankara, but undermine the U.S. position in Syria’s northeast. An SDF-Turkish confrontation is inevitable if Ankara crosses the border, and may happen even if Ankara chooses not to intervene. In Syria’s west, Russian support for Bashar al Assad ensures that external intervention will not prematurely end his rule, while the Iranian investment in the country has deepened, giving way to a reality that Tehran’s support for the regime in its war against the opposition has ensured that it will maintain a robust presence in the country for the foreseeable future. This fact is unlikely to change, no matter how many sanctions the United States imposes on Iranian officials. If the Syrian civil war has demonstrated anything, it is that the Iranians are willing to absorb the costs of intervention because the leadership has determined ensuring Assad’s survival is a core national security interest for the Iranian regime.

Winding Down the American Presence and Engaging Others

Stepping back, it is hard to see how the United States and Turkey can ever compromise in Syria. The SDF is the enabler of American combat operations in Syria. The Trump administration has chosen to remain in Syria, requiring support from a local force. The SDF and Turkey are hostile actors, with competing agendas. This is the reality of the situation. A compromise would entail Ankara acquiescing to the American vision for the SDF, which is a step too far for Ankara. A U.S. compromise with Ankara would require Ankara agreeing to accept the SDF as a legitimate actor, and not a terrorist group, whose leadership is committed to attacking Turkey. The U.S. is, now, essentially beholden to the decisions of an ally, Turkey, and its partner, the SDF. In each case, there are hard limits on the concessions that Washington can extract from these parties, owing to these entities’ own security interests.

The end result is that Washington’s core mission in Syria has now shifted from combat operations to simply trying to keep two hostile parties from shooting at each other. This is not a good place to be in, nor an open-ended mission that the U.S. military is suited for (or should even be doing). This reality should prompt Washington to hasten its efforts to end this conflict on terms it can accept, beginning with a recognition that any serious effort to wind down the American presence will entail open-ended talks with Russia. Turkey, as a bordering state with troops in Syria, must also be engaged, alongside the SDF, which sacrificed a generation of its men and women to fight Islamic State. This effort must recognize that the regime will remain, as a basis for the start of dialogue, but be firm on the need for Assad to face consequences for the murder of his own people on such a mass scale. Absent a broader, U.S.-Russia compromise on what a future Syrian state could look like, talks with Turkey and the Kurds will revolve around the crisis of the day, and be beholden to the “will Ankara invade, or won’t it invade this week” cycle that has framed recent U.S.-Turkish relations. This cedes the advantage to Ankara and, ironically, the SDF, who can pressure the United States. To end this cycle, Washington needs to identify what it is prepared to live with in Syria, realize that talks with Moscow are inevitable to help reach a broader agreement, and use this as a basis to drive a policy that allows a U.S. exit, while minimizing the potential for a Turkish-Kurdish clash.

Aaron Stein is the director of the Middle East Program at the Foreign Policy Research Institute.

Image: Turkish armed forces