President Trump announced on Monday that he will pull U.S. troops from northern Syria. Our mission in the region is complete, he claimed: ISIS has been defeated, and some sort of stability has been reached. Trump is partly correct. Our peacekeeping presence in northern Syria has prevented the Islamic State’s rebirth and the ISIS caliphate has been largely reduced to rubble.

There’s just one problem: Trump is trusting Turkish President Recep Tayyipp Erdoğan to fill the U.S. void and keep the peace.