Not his only mistake, but certainly one of his largest.
Well, maybe
@libertybele .
OR---The Kurds voluntarily reintegrate with the Syria Army and as such, have Syria's and by extension, Russia's protection from the Turks. (Done and done)
The US will "broker" a buffer zone and refugee transfer with Turkey and Syria … so there'll be no reason or opportunity to slaughter Kurds (unless the Kurds choose to ignore the buffer. If they do this, we'll know for certain the suicide gene is strong in the Kurd bloodline).
Any living remnants of ISIS in Syria won't be by year's end, by any means available--- and our hands will be clean.
Slowly peace returns to a unified Syria and in the Christmas/New Year season of goodwill we hear a "our long national nightmare is over" speech from Assad.
Turkey calls for new elections. Erdogan drowns in his own flop sweat.
We of course, are happy to contribute to the Syrian Marshall Plan.
I dare anyone to call this outcome I've just described a "mistake" -- large or otherwise.