The Turks decisively defeated the Crusaders, who lost an estimated four-fifths of their army near the mountains of Paphlagonia at Mersivan (Mersifon).
The Crusaders were organised into five divisions: the Burgundians, Raymond IV, Count of Toulouse and the Byzantines, the Germans, the French, and the Lombards.
The Turks had been troublesome to the Latins for some days, ensuring that they went where Kilij Arslan I wanted them to be and making sure that they only found a small amount of supplies.
Not only did they fail to open the Turkish lines, they were unable to return to the main crusader army and had to take refuge in a nearby stronghold.
The battle continued into the next day, when the crusader camp was captured and the knights fled, leaving women, children, and priests behind to be killed or enslaved.