[5][6] A folk legend claimed that Subutai wished to die by his son Uriyangkhadai by the banks of the Danube river.
[2] Uriyangkhadai led successful campaigns in the southwest of China against the Dali Kingdom alongside Kublai Khan and pacified tribes in Tibet after Kublai Khan's return to northern China, before turning east towards the kingdom of Đại Việt under the Trần dynasty by winter 1257.
[8] In the autumn of 1257, Uriyangkhadai addressed three letters to the Vietnamese monarch Trần Thái Tông demanding passage through to southern China.
[9] After the three successive envoys were imprisoned in Thang Long (modern-day Hanoi), the capital of the northern Vietnamese kingdom of Dai Viet,[10] Uriyangkhadai invaded Đại Việt with generals Trechecdu and Aju in the rear.
[8][11][3] While Chinese source material incorrectly stated that Uriyangkhadai withdrew from Vietnam after nine days due to poor climate, his forces did not leave until 1259.