In 1161, when Digunai invaded the Southern Song dynasty to unify China under the Jin dynasty's rule, he also sent agents to assassinate many of his own relatives and thus to cement his power within the imperial clan. Wulu, who was on the hit list, started a rebellion against the emperor. The rebellion was supported by many Jurchen officers and aristocrats who were dissatisfied with Digunai's policy of cultural sinicisation and administrative centralisation, and the human cost of the emperor's southern adventure. The first military officer to support the rebellion was Wanyan Mouyan (). Digunai lost the Battle of Caishi against the Song dynasty and was assassinated by his own disaffected officers. Wulu was able to become the new emperor without having to struggle against Digunai whose title he demoted down to Prince Yang of Hailing.