Around New Years 377, Former Qin launched a major attack against Dai. Tuoba Shiyijian temporarily fled his capital Yunzhong (雲中, in modern Hohhot, Inner Mongolia), but returned after Former Qin retreated. After his return, however, his nephew Tuoba Jin () convinced his oldest surviving son Tuoba Shijun () that Tuoba Shiyijian was considering naming one of the sons of his wife Princess Murong (a Former Yan princess) as heir and killing him. In response, Tuoba Shijun ambushed his father and brothers and killed them. This led to a collapse of Dai forces, and Former Qin forces occupied Yunzhong without a fight.