Battle of Qatwan
1141 CE.
Shown on the map at 39.800°, 66.900°.
The Battle of Qatwan (Chinese: 卡特萬之戰) was fought in September 1141 between the Qara Khitai (Western Liao dynasty) and the Seljuk Empire and its vassal-state the Kara-Khanid Khanate. The battle ended in a decisive defeat for the Seljuks, signaling the beginning of the end of the Great Seljuk Empire.
Text from the Wikipedia article Battle of Qatwan, licensed CC BY-SA 4.0.