by Murong Chui's son Murong Lin the Prince of Zhao, helped Tuoba Gui to put down the rebellion. A 387 joint operation between Northern Wei and Later Yan finally crushed Liu Xian's power. However, Tuoba Gui was having designs against Later Yan and, when he sent his cousin Tuoba Yi () the Duke of Jiuyuan to offer tributes to Murong Chui for him in 388, he asked Tuoba Yi to carefully examine the situation at the Later Yan court to observe any weaknesses. Murong Chui, displeased that Tuoba Gui did not personally come to pay tribute, interrogated Tuoba Yi, but allowed him to depart. Tuoba Yi reported to Tuoba Gui that, in his opinion, Murong Chui was old, his crown prince Murong Bao was weak, and that Murong Chui's brother Murong De the Prince of Fanyang was overly ambitious, which should cause internal problems for Later Yan upon Murong Chui's death. He opined that while Tuoba Gui should not attack Later Yan at that time, once Murong Chui died, there would be opportunity to do so. Despite his planning, however, he continued joint operations with Later Yan, and in 390 and 391, he and Murong Lin defeated the Helan (), Getulin (), and Gexi () tribes together. However, later in 391, an incident would occur that would cause the states to break relations. Tuoba Gui sent his brother Tuoba Gu () to offer tributes to Murong Chui. Murong Chui's sons and brothers had Tuoba Gu detained and ordered Tuoba Gui to offer good horses in exchange for Tuoba Gu's freedom. Tuoba Gui refused and further broke relations with Later Yan, entering into an alliance with Later Yan's rival for legitimate succession to Former Yan, Western Yan's emperor Murong Yong. Tuoba Gu, meanwhile, was kept under detention by Later Yan, albeit treated as an honored guest otherwise. In 394, when Murong Chui led a campaign against Western Yan that eventually led to Western Yan's destruction, Tuoba Gui sent a relief force, commanded by his cousin Tuoba Qian () the Duke of Chenliu and the general Yu Yue (), but was unable to save Western Yan. Later Yan campaign prior to the Battle of Canhe Slope By 395, Tuoba Gui was not only no longer submissive to Later Yan, but was openly pillaging other tribal vassals of Later Yan. Murong Chui, despite contrary counsel from his advisor Gao Hu (), decided to