The Battle of Köse Dağ (1243)

In the 1230s the Mongols took Iran and the Caucasus and reached the borders of Anatolia. In 1242 their general Baiju took and plundered Erzurum, and in 1243 he invaded again with about 30,000 Mongols and Georgian and Armenian auxiliaries.

Sultan Kaykhusraw II raised a large army, but it was made up of disparate contingents and lacked the Mongols' discipline. Ignoring the cautious advice of experienced nobles, he attacked in the pass of Köse Dağ between Sivas and Erzincan on 26 June 1243. The fighting was even for most of the day, but towards evening the Seljuk army began to break up and withdrew during the night.

Suspecting the empty camp was a trap, Baiju did not pursue the sultan. But the Mongols took cities such as Sivas, Kayseri and Tokat and imposed a heavy yearly tribute. After Köse Dağ the Seljuk sultanate declined, and Turkmen beyliks later arose on its lands.