Nayan (Mongol Prince) 'Prince of Kwang-ning'. In addition, Nayan was also the foremost leader of the Eastern "ulus"es (tribal groupings and districts ruled by Mongol appanage princes) dominated by the descendants of the brothers of Genghis Khan. Whatever the precise extent of Nayan's appanage, he certainly held sufficient lands within and around Manchuria to give him a power-base from which to launch a rebellion against his kinsman Kublai Khan. Nayan is represented as embodying a traditional Mongol reaction against the increasing sinicisation shown by Kublai Khan and his administration. Nayan adhered to the ancestral nomadic values of the Mongols and was dismayed at
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