As Iraq’s Shiite militias attack Islamic State positions southwest of Mosul, a confrontation could be looming with Turkey over the city of Tal Afar. Comprising predominantly ethnic Turkmen, the town is significant to Turkey's President, Recep Tayyip Erdogan, who is insisting that his country has historical claims in the region dating back to the Ottoman Empire. Turkmen are an ethnic minority in northern Iraq sharing a Turkic heritage with Turkey. The former Ottoman stronghold...