Mongol Empire What is referred to in English as the Mongol Empire was called the "Ikh Mongol Uls" ("ikh": "great", "uls": "state"; Great Mongolian State). In the 1240s, one of Genghis's descendants, Güyük Khan, wrote a letter to Pope Innocent IV which used the preamble "Dalai (great/oceanic) Khagan of the great Mongolian state (ulus)". After the succession war between Kublai Khan and his brother Ariq Böke, Ariq limited Kublai's power to the eastern part of the empire. Kublai officially issued an imperial edict on 18 December 1271 to name the country Great Yuan ("Dai Yuan", or "Dai Ön Ulus") to establish the
Nayan (Mongol Prince) support Nayan's rebellion, Kaidu remained a potent threat for the remainder of Kublai Khan's life. Kublai chose not to regard Nayan's Nestorian Christian co-religionists as guilty by association, and refused to allow them to suffer any level of persecution within his lands. In the wake of the suppression of Nayan's rebellion, Kublai Khan was able to begin to fully incorporate the lands and peoples previously dominated by the appanage princes into his domain. Nayan (Mongol Prince) Nayan was a prince of the Borjigin royal family of the Mongol Empire. He raised a noteworthy and serious rebellion against the Mongolian Khagan,