Kurdish fighters have allowed Syrian government forces into the outskirts the strategic northeastern city of Manbij to try to block Turkish-supported groups. This is the most visible outcome so far of U.S. President Donald Trump’s decision to hastily withdraw American forces from the country. However, U.S. troops are still in the process of leaving and it’s unclear whether other members of the international coalition fighting ISIS remain in the area, any of who may be at risk of getting caught up in any ensuing fighting. The Kurdish People’s Protection Units, or YPG, issued a statement welcoming the Syrian Arab Army into Manbij on Dec. 28, 2018. The Syrians issued their own, triumphantly declaring their arrival from the southwest, on the same day. This comes as Turkish forces and the Turkish-backed Free Syrian Army, or TFSA, have begun moving toward the city from the northwest, with the goal of uprooting the Kurdish fighters, which Turkey views as terrorists that threaten its national interests.

“We invite the Syrian government forces ... to assert control over the areas our forces have withdrawn from, in particular Manbij, and to protect these areas against a Turkish invasion,” the YPG said in their press release. “Out of the commitment of the Syrian army to handle its responsibilities, and upon the calls of the people of Manbij, the general command of the Syrian army declares entering Manbij and hosting the Syrian flag in it,” the Syrian Arab Army’s statement read.

Long-standing tensions For years now, the YPG has been the primary contributor of forces to the Syrian Democratic Forces, or SDF, which has received its support from the U.S.-led coalition fighting ISIS in Iraq and Syria. Turkish threats to intervene in Syria against the Kurds prompted the public deployment of American forces in and around Manbij in 2017 to keep the two parties apart. But the area had been of critical importance well before then. Manbij has been a major, strategic hub in northeastern Syria, sitting on a major highway that connects northwestern cities, such as Aleppo, with population centers in the eastern portion of the country. Rebels fighting the Syrian government took control of the city in 2012, but lost it to ISIS in 2014. Two years later, the SDF, supported by American air strikes and special operations forces, liberated it from the terrorist group.

DOD A map showing various points of interest in Syria, including Manbij in the north.

The Turkish government views the YPG as a terrorist group, inseparable from the Kurdish Workers Party, or PKK, which operates in Turkey and along that country’s border areas in Syria and Iraq. In January 2018, the Turks launched a major offensive into the northwestern Syrian cantonment of Afrin to eject the Kurdish fighters. At the time, this prompted similar appeals from the YPG to Assad, as well as his Russian benefactors, though they were ultimately not enough to prevent Turkey from establishing its own occupied buffer zone in northwestern Syria. The United States said that any groups that left the SDF to aid the YPG in Afrin would no longer be eligible for American support. Now, Trump’s snap decision to pull American forces out of Syria entirely within months, which he announced on Dec. 19, 2018, has put the SDF as a whole, as well as U.S.-backed civil authorities in cities across northeastern Syria, in limbo. For its part, the U.S. military has rejected the new reports that Syrian forces had entered Manbij proper, a technicality that ignores the significance of the Syrian Arab Army, and potentially militias aligned with Syria's dictator Bashar Al Assad, taking up positions along the city’s southwestern flank. Dozens of U.S. special operations forces and supporting personnel remain in the city center, where they had been working hand-in-hand with SDF forces and local civilian officials.

More recently, Turkish President Recep Tayyip Erdoğan threatened to extend the area of operations for his forces eastward and that his military would fight its way through its ostensible American allies to crush the YPG if necessary. Since Trump’s withdrawal announcement, Turkey has pledged to both defeat the Kurds and the remnants of ISIS, which the SDF is still in the process of containing to try to prevent those terrorists from staging a major comeback. Any distraction from those operations will only give ISIS breathing room to regroup.

US Army Turkish and American armored vehicles on patrol near Manbij in November 2018. This was one of a number of confidence-building measures the United States had hoped would stave off a major Turkish intervention in the region before Trump's decision to pull out of Syria entirely.

Shifting allegiances Erdoğan has sought to temper concerns about an all-out conflict with the Syrians, framing the developing situation as one in which his forces and those of the Syrian government can stand together as “terrorists.” The dispute with the United States over support for the Kurds has pushed Turkey closer to Russia, as well as the Syrian government, in recent years. Turkish authorities, together with their counterparts from Russia and Iran, have been working together on a separate political solution to the Syrian civil war. “In the current situation, we are still supporting the integrity of Syrian soil,” Erdoğan told reporters on Dec. 28, 2018. “These areas belong to Syria. Once the terrorist organizations leave the area, we will have nothing left to do there.” Whether or not this is actually true is debatable. Turkey also has a history of supporting ethnic Arab and Turkmen groups opposed to Assad, many of whom are now part of the TFSA, and would likely be interested in resuming that fight in earnest in the future. In addition, the Turkish government was instrumental in blocking a planned Syrian government offensive into the western governorate of Idlib, seen as the last major bastion of anti-Assad rebels, in September 2018.

AP Turkish President Recep Tayyip Erdoğan, at center, shakes hands with Russian President Vladimir Putin, at right, and Iranian President Hassan Rouhani, at left, during a meeting in Ankara about the future of Syria in April 2018.

A test case in Manbij Regardless, the situation in Manbij is a prime example of just how rapidly the situation is already changing in Syria, even before American forces have completed their expected withdrawal. It exposes just how quickly a major rift between the United States and its erstwhile Kurdish partners has emerged, as well. President Trump has expressed his faith in Turkey’s ability to continue the fight against ISIS. At the same time, it’s unclear whether the United States would have any plans to come to the aid of its NATO ally should Turkish or Turkish-backed forces find themes in open conflict in northeastern Syria with an alliance of convenience between Kurdish groups and the Syrian Arab Army.