Berke Khan (died 1266) (also Birkai; , ) was a grandson of Genghis Khan and a Mongol military commander and ruler of the Golden Horde (division of the Mongol Empire) who effectively consolidated the power of the Blue Horde and White Horde from 1257 to 1266. He succeeded his brother Batu Khan of the Blue Horde (West), and was responsible for the first official establishment of Islam in a khanate of the Mongol Empire. Following the Sack of Baghdad by Hulagu Khan, his cousin and head of the Mongol Ilkhanate based in Persia, he allied with the Egyptian Mamluks against Hulagu. Berke also supported Ariq Böke against Kublai in the Toluid Civil War, but did not intervene militarily in the war because he was occupied in his own war against Hulagu and the Ilkhanate. Name Berke is a name used by both Turkic peoples and Mongols. In Mongolian berke (cf. bärk in Old Turkic) means "difficult, hard". Birth Berke was born to Jochi, the eldest son of Genghis Khan. There is no clear consensus regarding the year of Berke's birth. Mamluk ambassadors visiting him in 663 AH (1264/5) described him as fifty-six years old. This gives him a birth date somewhere between 1207 and 1209. However, contemporary Persian chronicler Juzjani claims that Berke was born during the Mongol conquest of Khwarezmia, which took place between 1219 and 1221. The latter claim was used to support the argument of historian Jean Richard that Berke's mother was Khan-Sultan (or Sultan Khatun), the captured daughter of Muhammad II of Khwarazm. The marriage between Jochi and Khan-Sultan took place in 1220, allowing Berke's birth to be no earlier than 1221. Background Berke was present, with several of his brothers, at the inauguration of his uncle Ögedei as Great Khan in 1229. In 1236, Berke joined his brothers Orda, Sinkur, and Shiban and an assortment of cousins under the leadership of Batu Khan in a vast army, comprising some 150,000 soldiers, which marched from Siberia and into the territory of the Muslim Volga Bulgars and Kipchaks, whom they subdued. Batu and Subutai sent Berke to the country north of the Caucasus to conquer the Kipchaks there. Next they devastated the principalities of Ryazan and Suzdal in 1237, and marched further into Russia. During the winter of 1238–39, Berke defeated the Kipchaks and imprisoned the chief of the Merkits. He afterwards subdued the steppe watered by