President Recep Tayyip Erdoğan has announced that Turkey is conducting a "landmark" military operation in Syria's Idlib governorate, extending the area brought under the control of Ankara and its rebel allies in last year's Operation Euphrates Shield against ISIS. Now the target is Hayat Tahrir al-Sham (HTS). a formation led by militias to emerge from the former Nusra Front, some with apparent ties to al-Qaeda. (Al Jazeera, Oct. 9; Daily Sabah, Oct. 7) The Euphrates River has emerged as a border between Turkey's de facto "buffer zone"in northern Syria and areas still under Kurdish control—for now. However, Kurdish enclaves still remain west of the river, including the likely flashpoint town of Afrin. (See map.)

Russia is meanwhile installing a new S-350 Vityaz air-defense system at its coastal base of Tartus, pointing again to Moscow's plans for a long-term military presence in Syria. (Aldorars, Sept. 24)

Kurdish-led Syrian Democratic Forces continue their advance on the principal ISIS-held town of Raqqa—and have been repeatedly accused of attacks on civilians. The genuinely heroic media activists of Raqqa is Being Slaughtered Silently, who have risked their lives to report on ISIS abuses in the city over the past years, have now accused the SDF of killing civilians and indiscriminate attacks on outlying areas. (Syria News, Oct. 2; Al Bawaba, Sept. 28)

The reckoning at ISIS-held Deir ez-Zor on the Euphrates—with Russian-backed Assad forces advancing from the west and US-backed Kurdish forces advancing from the east—has been forestalled for the moment, as ISIS has pushed back the advance by regime forces. (EA Worldview, Sept. 30)

But a similar reckoning may be brewing at Raqqa, where RBSS now reports that Assad forces have advanced into the eastern countryside of that governorate, seizing several villages.

The threat of Arab-Kurdish ethnic war—which could also be a proxy war by regional rivals Turkey and Russia—continues to loom over the collapse of ISIS in northern Syria. The defeat of the Islamic State could, perversely, only open a larger war in Syria—and potentially beyond its borders as well.