In the chess game in Idlib, which has seen both collaboration and rivalry between Turkey and Russia, Ankara was placed in check for the first time this week. The Syrian army and its allies captured Khan Sheikhoun, a key town in the rebel-held province, soon after they resumed their offensive on Idlib as Turkey reached a deal with the United States to jointly create a safe zone in Kurdish-held areas east of the Euphrates River. 

The fall of Khan Sheikhoun marks a major debacle for the rebel forces and puts Turkey inside the circle of fire. The Turkish military’s base at Morek — one of the 12 Turkish observation posts set up around Idlib as part of a de-escalation plan — is now under a siege by the Syrian army. Foreign Minister Mevlut Cavusoglu said Turkey has no intention of retreating, with Russian and Turkish military officials starting talks Aug. 21 to decide the fate of the Morek outpost. 

There is ample reason to suggest that the thrust on Khan Sheikhoun was a response to Turkey’s plan to set up a joint operation room with the United States under the safe zone accord, a move that will change the equilibrium in Syria. The accord, announced Aug. 7 at the end of Turkish-US talks in Ankara, alarmed Russia over Turkey’s intentions. Moscow was already wary that Turkish President Recep Tayyip Erdogan could play a double game as it sought to maintain strategic cooperation with Ankara, both through the Astana process and the sale of the S-400 air defense systems.