Western Yan
In fall 391, an incident occurred that would lead to the break of relations between Later Yan and Northern Wei. That year, Tuoba Gui sent his brother Tuoba Gu to Later Yan to offer tribute, and Murong Chui's sons detained Tuoba Gu and ordered Tuoba Gui to offer horses to trade for Tuoba Gu's freedom. Tuoba Gui refused and broke off relations with Later Yan, instead entering into an alliance with Western Yan.