The fall of rebel-held eastern Aleppo in Syria last month was a stunning personal blow for Turkish President Recep Tayyip Erdogan, whose government had openly backed Syrian rebel groups after the civil war began in 2011. Losing the rebels’ self-styled “capital of the revolution” to Syrian President Bashar al-Assad and his allies is an insurmountable setback for years of Turkish regime-change efforts in Syria.

But there is a silver lining for Turkey. After Aleppo, Ankara can focus all its diplomatic, military and political efforts on pursuing its more immediate national security interests in northern Syria: fighting the so-called Islamic State while checking the Syrian Kurdish project for autonomy and national independence. And with President Barack Obama serving his last few days in Washington, Erdogan sees a small window of opportunity to maximize his leverage and negotiating position on both these fronts before President-elect Donald Trump moves into the White House. ...