Sartaq Khan
Sartaq (or Sartak, Sartach, Mongolian: Сартаг) Khan (died 1256) was the son of Batu Khan and Regent Dowager Khatun Boraqcin of Alchi Tatar. Sartaq succeeded Batu as khan of the Ulus of Jochi (Golden Horde or Kipchak Khanate).
In 1252, Alexander Nevsky met with Sartaq at Sarai. Alexander received yarlyk (license) to become Grand Duke of Vladimir in vassalage to the Kipchak Khanate. According to Lev Gumilev he became Sartaq's anda (sworn brother, probably akin to blood brother) and an adopted son of Batu Khan.
Sartaq was reputed to be a Christian convert (presumably Nestorianism); though his father was a Shamanist. There are several stories of Sartaq's conversion. The Armenian writers, for example, alleged that Sartaq was brought up and baptized among the Russians.
However, a message dated August 29, 1254 by Sartaq addressed to Pope Innocent IV, stated that Sartaq, then a duke, was baptized as a Christian. The Pope heard the news from a priest whom the khan had sent as envoy to the papal court.
His reign as khan of the Golden Horde was short-lived. He died in 1256 before returning from Great Khan Möngke's court in Mongolia, less than one year after his father, probably having been poisoned by his uncles Berke and Berkhchir. The notable Russian historian Karamzin, along with Armenian and Muslim chroniclers, stated that they were hostile to one another because of tensions between religions. Sartaq was succeeded by Ulaqchi briefly in 1257, before his uncle Berke succeeded to the throne. It is not clear whether Ulaqchi was his brother or his son.
Sartaq's daughter Theodora (or Theothiure) was the wife of Gleb Vasilkovich first Prince Belozersky of Beloozero and Rostov, a grandson of Konstantin of Rostov and first cousin once removed of Alexander Nevsky. Their descendants include Ivan IV of Russia and innumerable families of Russian nobility.