In 391, Murong Bao was, in all likelihood, involved in an incident that would fatefully lead to the breakup in relations with Later Yan's vassal Northern Wei. That year, Northern Wei's prince Tuoba Gui sent his brother Tuoba Gu (拓拔觚) to offer a tribute to Later Yan. Traditional historians record that Murong Chui's sons and brothers (plural, but by this point would be led by Murong Bao) detained Tuoba Gu and demanded that Tuoba Gui ransom him by offering horses. Tuoba Gui refused, and Tuoba Gu was not permitted to leave, and the relationship between Later Yan and Northern Wei was gone. Tuoba Gui entered into an alliance with Western Yan, and later, even after Western Yan was destroyed by Later Yan in 393, continued to harass Later Yan's border lands. In 395, Murong Bao, along with his brothers Murong Nong and Murong Lin, led an 80,000-men expedition that was intended to punish Northern Wei for its recalcitrance—but one that would have fateful consequences for Later Yan.