Mongols defeat Seljuks at Kose Dag

June 26, 1243

The Mongol general Baiju crushed the Sultanate of Rum in a mountain pass in eastern Anatolia. The Seljuk state collapsed into vassalage, leaving a patchwork of Turkish beyliks that, half a century later, would include a small frontier emirate under one Osman. The battle effectively ended Seljuk independence and opened Anatolia to the Mongol sphere, reshaping the political landscape of the entire region.