|Battle of Qatwan|
Great Seljuq Empire|
|Commanders and leaders|
Garshasp II †
|20,000 - 700,000 (exaggerated Muslim figure)||100,000|
|Casualties and losses|
The Battle of Qatwan (Chinese: 卡特万之战) was fought in September 1141 between the Qara Khitai (Western Liao Empire) and the Seljuq Empire and its vassal-state the Kara-Khanids. The Seljuqs were decisively defeated, which signalled the beginning of the end of the Great Seljuk Empire.
The Khitans were people of the Liao Dynasty who moved west from Northern China when the Jurchens invaded and destroyed the Liao Dynasty in 1125. They were led by Yelü Dashi who took the Eastern Karakhanid capital of Balasaghun. In 1137, they defeated the Western Karakhanids, a vassal of the Seljuks, at Khujand, and the Karakhanid ruler Mahmud II appealed to his Seljuk overlord Ahmed Sanjar for protection.
In 1141, Sanjar with his army arrived in Samarkand. The Kara-Khitans, who were invited by the Khwarazmians (then also a vassal of the Seljuks) to conquer the lands of the Seljuks, and also responding to an appeal to intervene by the Karluks who were involved in a conflict with the Karakhanids and Seljuks, also arrived. 
Widely varying figures from different sources were given for the Kara-Khitan forces, ranging from 20,000 to 300,000, and 700,000, while the Seljuk forces ranged from 70,000 to 100,000. The Kara-Khitans were also said to have been given a reinforcement of 30,000-50,000 Karluk horsemen. While many Muslim sources suggested that the Kara-Khitan forces greatly outnumbered the Seljuks, some contemporary Muslim authors also reported that the battle was fought between forces of equal size.
On the Qatwan steppe, north of Samarkand, the battle was joined. The Khitan divided their armies into three contingents, with the smaller left and right flanks holding 2,500 men. The Kara-Khitans attacked the Seljuks forces simultaneously, encircled them, and forced the Seljuq center into a wadi called Dargham, about 12 km from Samarkand. Faced with no way out, the Seljuq army was destroyed and Sanjar barely escaped. Figures of the dead ranged from 11,000 to 100,000. Among those captured at the battle were Seljuq military commanders and Sanjar's wife.
Yelü Dashi spent ninety days in Samarkand, accepting the loyalty of Muslim nobles and appointing Mahmud's brother Ibrahim as the new ruler of Samarkand. However, Yelü did allow the Muslim Burhan family to continue to rule Bukhara. After this battle, Khwarazm became a vassal state of the Kara-Khitan. In 1142, Yelü sent Erbuz to Khwarazm to pillage the province, which forced Atsiz to agree to pay 30,000 dinars annual tribute.
- Journal of Central Asia", Vol. 16, (Centre for the Study of the Civilizations of Central Asia, 1993), 19.
- Asimov, M. S., The Historical, Social and Economic setting, (Motilal Banarsidass, 1999), 238.
- "The Historical Prester John", Charles E. Nowell, Speculum, Vol. 28, No. 3 (Jul., 1953), 442.
- Biran, Michal (2001). ""Like a Might Wall:" The armies of the Qara Khitai" (PDF). Jerusalem Studies in Arabic and Islam. 25: 44–91. Archived from the original (PDF) on 2015-12-10. Retrieved 2016-08-02. Cite uses deprecated parameter
- The Historical Prester John, Charles E. Nowell, 442.
- "Dailamīs in Central Iran: The Kākūyids of Jibāl and Yazd", C. E. Bosworth, Iran, Vol. 8, (1970), 90.,
- Biran, Michal (2005). The Empire of the Qara Khitai in Eurasian History: Between China and the Islamic World. Cambridge University Press. p. 42. ISBN 0521842263.
- Biran, Michal. (2005), pp 41-43.
- Biran, Michal. (2005), pp. 43–44.
- 遼史 Liao Shi, volume 30, biography of Yelü Dashi.
- Biran, Michal. (2005), 44.
- Biran, Michal. (2005), 44.
- Asimov, 238.