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
Mongol invasions of Vietnam repeatedly ignored demands to attend the Yuan court and offer his personal submission to the Great Khan. By 1266, a standoff developed, as the Emperor Thánh Tông sought a loose tributary relationship, while Kublai demanded full submission. Trần Thánh Tông sent an official letter requiring Kublai to take his darughachi back. Because of civil war in the Mongol Empire, and the Yuan conquest of Song China, armed conflict was delayed. Instead, Kublai reminded him of the peace treaty signed by the Mongols and Đại Việt. As a result of the Mongol conquest of the Song Empire, by 1278–79, Mongol troops