Battle of Köse Dağ

The Battle of Köse Dağ took place in eastern Anatolia on 26 June 1243 when an army of the Sultanate of Rum, led by Sultan Kaykhusraw II, confronted an invading Mongol army under the general Baiju and was decisively defeated. The battle was the pivotal event of the Mongol conquest of Anatolia: Rum, previously a significant independent power in the eastern Mediterranean, was reduced to the status of a client kingdom, and its territories were later absorbed into the Mongol Ilkhanate.

The Mongol Empire first achieved territorial contact with Rum in the early 1230s by conquering a large swathe of western Iran, but largely left it alone over the next decade. Instead, under their general Chormaqan, Mongol armies subjugated Transcaucasia and reduced the Kingdom of Georgia to a vassal state. Relations deteriorated after the accession of Kaykhusraw II to the Rum throne in 1237, and Mongol raids on Rum territory began in 1240. Two years later, Baiju, who had replaced Chormaqan after the latter became disabled, captured and pillaged the city of Erzurum, escalating hostilities into open war. He again invaded Rum in 1243, with an army of 30,000 Mongol troops accompanied by Georgian and Armenian auxiliaries.

Kaykhusraw built a large army to confront the invasion, but his 80,000-strong force lacked the discipline and cohesion of the Mongols. He ignored the cautious advice of experienced nobles under his command, and attacked his enemy on the pass of Köse Dağ Mountain on 26 June. For most of the day, the army of Rum appeared to be slightly superior, but it started to disintegrate late on. The apprehensive army of Rum fled during the night; Baiju missed the opportunity to capture the Sultan because he suspected the deserted enemy camp was a trap. Nevertheless, the Mongols captured several cities following their success at Köse Dağ, and exacted a vast annual tribute from their enemy. Rum never recovered from this critical defeat.