Battle of Köse Dağ

The Battle of Köse Dağ was fought between the Seljuk Turks of Anatolia and the Mongols on June 26, 1243 at the defile of Köse Dağ (Ch'man-katuk Չման-կատուկ), a location between Erzincan and Gümüşhane in northeast Anatolia, modern Turkey, that ended in a decisive Mongol victory.

Background
During the reign of Ögedei, the Seljuks of Anatolia offered friendship and a modest tribute to Chormaqan. Under Kaykhusraw II, however, the Mongols began to pressure the Sultan to go to Mongolia in person, give hostages, and accept a Mongol darugachi.

The battle
Under the leadership of the commander Bayju, the Mongols attacked the Seljuk Sultanate of Anatolia in the winter of 1242-43 and seized the city of Erzurum. Sultan Kaykhusraw II immediately called on his neighbours to contribute troops to resist the invasion. The Empire of Trebizond sent a detachment and the sultan engaged a group of "Frankish" mercenaries. A few Georgian nobles such as Shamadavle of Akhaltsikhe also joined him, but the majority of the Georgians were compelled to fight alongside their Mongol masters.

The decisive battle was fought at Köse Dağ on June 26, 1243. The primary sources do not record the size of the opposing armies but suggest that the Mongols faced a numerically superior force. Bayju brushed aside an apprehensive notice from his Georgian officer regarding the size of the Seljuk army, stating that they counted as nothing the numbers of their enemies: "the more they are the more glorious it is to win and the more plunder we shall secure", he replied.

The Seljuk commander, Kaykhusraw II, rejected the proposal of his experienced commanders to wait for the Mongol attack. Instead, he sent a force of 20,000 men, lead by inexperienced commanders, against the Mongol army. The Mongol army, pretending a retreat, turned back, encircled the Seljuk army and defeated it. When the rest of the Seljuk army witnessed their defeat, many Seljuk commanders and their soldiers, including Kaykhusraw II, started to abandon the battlefield. Eventually, the Seljuk army was left without leaders and most of their soldiers had deserted, without seeing any combat.

After their victory, the Mongols took control of the cities of Sivas and Kayseri. The sultan fled to Antalya but was subsequently forced to make peace with Bayju and pay a substantial tribute to the Mongol Empire.

Aftermath
The defeat resulted in a period of turmoil in Anatolia and led directly to the decline and disintegration of the Seljuk state. The Empire of Trebizond became a vassal state of the Mongol empire. Furthermore the Armenian Kingdom of Cilicia became a vassal state of the Mongols. Real power over Anatolia was exercised by the Mongols. After a long period of fragmentation, Anatolia was unified by the Ottoman dynasty.