The Kurds keep remaking the Middle East.

Syrian Kurds are discovering that their vital role in the fight against ISIS may not have secured Washington’s help in their struggle against their other enemies. As a stateless people sandwiched between Syria and Turkey, two countries bent on keeping them down, they must rely on external backers such as the United States to give them a margin of freedom and autonomy. But the United States is a fickle friend indeed.

Last year, Iraqi Kurds had a foretaste of what can happen when you misread or ignore Washington’s strategic interests. Iraq’s Kurdish region held an independence referendum, hoping to gain leverage in negotiations with Baghdad about an eventual separation. The Trump administration warned them not to proceed, citing poor timing, as the fight against ISIS was still ongoing. The administration then did nothing when Baghdad imposed heavy sanctions on the region and forcibly took disputed territories back from Kurdish control. The Iraqi Kurdish leaders learned that a global power won’t rush to their aid if they threaten its interests: in this case, protecting the fight against ISIS and preserving a unified Iraq as a bulwark against Iranian influence.

Today, the YPG faces a similar predicament. It is a Syrian affiliate of the Kurdistan Workers’ Party (PKK), which has fought an insurgency against the Turkish state since the 1980s; Turkey, the United States, and the European Union have designated the PKK a terrorist organization. Despite the YPG’s shared genealogy with the PKK, Washington supported the group because of its battlefield prowess. As it beat back ISIS, the YPG took control of additional non-Kurdish territory in Syria, including the mostly Arab cities of Manbij and Raqqa.

But with the Assad regime resurgent, all those gains could be reversed. Aided by control of the skies over much of Syria and its veto power in the United Nations Security Council, as well as ground forces supplied by Iran and its allied militias, Assad’s forces have taken back rebel-held territory over the past two years. They hope to finish the job in the coming months, and are primed to move on Idlib, the final rebel holdout. Soon after that, the regime will tell the YPG to give up the area it surrendered to the group in 2012. (It did so in order to free its own forces to fight off the popular uprising further south.) Assad needs the YPG-held region’s vast wheat fields and oil fields—Syria’s largest—to rebuild.

Who exactly are ‘the Kurds’?

Turkey, too, has an important stake: It does not want the YPG, and by extension the PKK, running a Kurdish enclave in Syria directly on its border. In February, Turkish forces invaded the Kurdish district of Afrin in northwest Syria, wresting it from the YPG as Russia and the United States stood by. The group now fears that the story will play out again in Syria’s northeast, not in the least because Turkey has said it wants to drive them out.