The best-known peace process in the Middle East today is the Israeli-Palestinian dialogue. But the most crucial one for the United States is the Turkish-Kurdish peace process that fell apart in 2015.

These negotiations aimed to end a 30-year conflict between the Kurdistan Workers’ Party (PKK) and the government of Turkey. They collapsed in part due to developments related to the war in neighboring Syria.

In 2014, the United States decided to back the Syrian Kurdish Peoples’ Protection Units (YPG) to fight ISIS. Ankara was threatened by the power and legitimacy this gave to the YPG and its political arm, the Democratic Union Party (PYD), directly on Turkey’s southern border. Ultimately, in order to counter Kurdish gains at home and in Syria, Turkish president Recep Tayyip Erdogan—who until then had been seen as a moderate Turkish leader capable of ending a conflict that had cost his country tens of thousands of lives and billions of dollars over decades—chose to return to war.

For years, Turkey claimed to be harmed by the Obama administration’s decision to back the YPG, which Turkey views as the Syrian wing of the PKK. For its part, the Obama administration failed to take the Turkish-Kurdish conflict and various possible outcomes for negotiations into account when choosing its counter-ISIS partners. It did not invest any diplomatic effort into encouraging either side to stick to negotiations when they began to deteriorate—despite the positive impacts of peace talks on the fight against ISIS.

The resumption of conflict after 2015 changed Turkey’s approach to the Syrian crisis and its broader geopolitical orientation. Erdogan, once a sworn enemy of Assad and backer of the Syrian uprising, turned the armed Syrian opposition into an anti-Kurdish proxy force with two military campaigns against the SDF and AANES. His government is now exploring normalization with the Syrian regime to crush Kurdish power in northeast Syria. Turkey’s need for a major power willing to support its anti-Kurdish ambitions in Syria drove it closer to Russia—both in the context of that conflict and beyond.

This reorientation poses imminent challenges to U.S. interests. Erdogan is currently threatening to invade North and East Syria and create a so-called ‘safe zone’ that could stretch as far as 50 kilometers into Syrian territory. Such an operation would collapse the capabilities of the Syrian Democratic Forces (SDF) and destroy the US-SDF partnership forever.

While the US cannot stay in Syria forever, it also cannot afford to walk away from this partnership now. ISIS was able to conduct tens of attacks last year, including a prison break in Hasakah that saw ISIS take control of the detention facility before the SDF and the Coalition could respond. According to the Pentagon, SDF forces continue to depend on US aerial assistance to insure the defeat of ISIS.

These attacks are a grave reminder that ISIS is still a problem—and that the reason it is not a bigger one is because of the SDF’s efforts. Without this partnership, the U.S. would have had to commit ground troops to fighting ISIS, and would have likely sustained far greater losses and spent far more money than the American people would have tolerated. Like in Afghanistan or Iraq, there would have been no plan for post-war governance or stability. Ending the partnership with SDF will end one of the most successful US missions in the region prematurely—threatening to undo all of its gains and create conditions that could lead to more conflict in the future.

Similarly, a hasty US withdrawal from Syria would hand Russia a significant diplomatic win. The U.S. partnership with the SDF is the only obstacle standing in the way of a complete Russian and regime reconquest of Syria. Allowing the SDF to be crushed by Turkey will eliminate U.S. political leverage in Syria and destroy the only political entity in the country that has the capability to demand concessions from the Assad regime that could benefit all Syrians as part of a political solution.

The best way to maintain the U.S.-SDF partnership, address Turkey’s security concerns in Syria, keep ISIS down, and promote a political solution to the Syrian conflict is to deal with the roots causes of instability in the northeast by ending the Turkey-PKK conflict through renewed peace negotiations.  In the early years of the fight against ISIS, the U.S. missed an opportunity to try to salvage Turkey-PKK peace talks and address the impact of its strategy on both sides’ positions in the negotiations. U.S. policymakers should not miss another opportunity to address immediate escalation and promote long-term stability by investing serious diplomatic effort in a new diplomatic solution.

(Photo: DELIL SOULEIMAN/AFP via Getty Images)