Murong Nuohebo, who was said to be young (although his age by that point is unknown), and who carried the title of Prince of Yan, became khan.
Tibet forces then attacked Tang as well, but were repelled by the Tang general Niu Jinda (牛進達), and, after receiving agreement from Emperor Taizong that a princess would be given to Songtsen Gampo in marriage, withdrew (that princess, Wencheng, would eventually marry Songtsen Gampo in 641).
Emperor Taizong created the daughter of a clansman as Princess Honghua and gave her to Murong Nuohebo in marriage.
When Murong Nuohebo heard of this plot, he fled to his general the Prince of Weixin, then stationed at Shanshan.
The Tang officer Xi Junmai (席君買) took this opportunity to ambush the Prince of Xuan and killed him and two of his brothers.
Tuyuhun, however, was said to be thrown into a state of confusion, and Emperor Taizong sent the official Tang Jian (唐儉) to help Murong Nuohebo pacify the people.
Emperor Gaozong sent the general Su Dingfang to command Tang forces to the west, to help protect Tuyuhun remnants, but carried out no actual military attacks against Tibet, although he sent emissaries to rebuke Tongtsen when Tongtsen subsequently sent emissaries to again make accusations against Tuyuhun and request another marriage with Tang.
However, the campaign was plagued by disagreements between Xue and Guo, and Tang forces eventually suffered a major defeat by Tongtsen's son and successor Gar Trinring at the Battle of Dafeichuan, ending hopes of allowing the Tuyuhun people to return.