Invasion of Yunnan and Tibet During the first phase of the Mongol conquest of the Song dynasty in southern China, Uriyangkhadai led 3,000 Mongol cavalry in
Sichuan. Uriyangkhadai had significantly more military experience than Kublai Khan and proved invaluable in battle. After the three successive envoys were imprisoned in
Thang Long (modern-day Hanoi), the capital of the northern Vietnamese kingdom of
Dai Viet, Uriyangkhadai invaded Đại Việt with generals Trechecdu and Aju in the rear. Around 17 November 1259 while besieging
Ezhou in
Hubei, Kublai Khan received a messenger who described Uriyangkhadai's army advances from Thang Long to
Tanzhou (modern-day Changsha) in
Hunan via
Yongzhou (modern-day Nanning) and
Guilin in Guangxi. Uriyangkhada's army subsequently fought its way north to rejoin Kublai Khan's army on the northern banks of the
Yangtze river, after which both armies returned to northern China due to
the succession crisis that emerged as a result of Möngke Khan's death at the
Siege of Diaoyucheng on 11 August 1259. ==References==