Excerpts from Books and Wikipedia
"The Battle of Köse Dağ was fought between the Sultanate of Rum ruled by the Seljuq dynasty and the Mongol Empire on June 26, 1243 at the defile of Köse Dağ, a location between Erzincan and Gümüşhane in modern northeastern Turkey; the Mongols achieved a decisive victory. . . . The defeat resulted in a period of turmoil in Anatolia and led directly to the decline and disintegration of the Seljuq 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." [Wikipedia]