office at Yonghung with local officials. Ordering defectors to build ships, the Mongols began attacking the coastal islands from 1255 on. In the Liaodong Peninsula, the Mongols formed Korean defectors into a colony of eventually 5,000 households. In 1258 the king and the Choe clan retainer Kim Jun staged a counter-coup, assassinated the head of the Choe family, and sued for peace. When the Goryeo court sent the future king Wonjong of Goryeo as hostage to the Mongol court and promised to return to Gaegyeong, the Mongols withdrew from Korea. Dali, Vietnam and Tibet Möngke concerned himself more with the war in China, outflanking the Song dynasty through the conquest of the Kingdom of Dali (in modern Yunnan) in 1254 and an invasion of Indochina, which allowed the Mongols to invade from the north, west, and south. Möngke Khan dispatched Kublai to the Dali Kingdom in 1253. The ruling family, Gao, resisted and murdered the Mongol envoys. The Mongols divided their forces into three. One wing rode eastward into the Sichuan basin. The second column under Uryankhadai took a difficult way into the mountains of western Sichuan. Kublai himself headed south over the grasslands, meeting up with the first column. With Uryankhadai galloping in along the lakeside from the north, Kublai took the capital city of Dali and spared the residents despite the slaying of his ambassadors. The Mongols appointed King Duan Xingzhi as local ruler and stationed a pacification commissioner there. After Kublai's departure, unrest broke out among the Black jang. By 1256, Uryankhadai, the son of Subutai, had completely pacified Dali. After subjugating the Dali, Kublai sent a column south under Uriyangkhadai, the son of Subutai. Uriyangkhadai sent envoys to ask the Vietnamese for a route to attack the Southern Song, but the Tran Vietnamese imprisoned the Mongol envoys. In 1257, a Mongol column under Uriyangkhadai invaded Vietnam (then known as Đại Việt) along with his son Aju and an army of 3,000 Mongols and 10,000 Yi tribesmen. They routed the Vietnamese army and sacked the capital Thăng Long (renamed Hanoi in 1831). Uriyangkhadai executed its inhabitants for the murder of the envoys. After staying in Thăng Long for a while, the Mongols fell ill due to the unfamiliar climate. Realizing that it was time to drive the Mongols out, the Vietnamese launched a counter-attack and won the decisive battle of Dong Bo Dau. To avoid further war,