"The Syrian government had been almost entirely absent from the northeast since it withdrew or was chased out by armed rebels."

"The Syrian Democratic Forces, a Kurdish-led militia that worked with the United States to fight the Islamic State, soon became the region’s overarching political force. Although the Syrian Kurds did not declare Mr. Assad’s government an enemy, Mr. Assad distrusted their efforts to establish self rule and vowed to retake all of Syria’s territory. But he had no way to do so, especially as American troops remained in the area. President Trump’s decision last week to move those troops out of the way of a Turkish incursion gave Mr. Assad an opening, and his forces began to fill it on Monday. In some towns, they were welcomed by locals who chanted nationalistic slogans and carried Mr. Assad’s photograph. In other areas, trucks drove large numbers of Syrian soldiers into the area to take up positions."

From "Syria Live Updates: Assad’s Forces Move Into Area Hit by Turkey" (NYT).

I'm also seeing there that the European Union countries have unanimously agreed to stop selling arm to Turkey, even though "Like most European Union nations, Turkey is a NATO member."