Murong Fuyun
In spring 619, Zhang Qide arrived in Liang territory. (By this point, Emperor Gaozu's son Li Shimin (the eventual Emperor Taizong) had already destroyed Xue Rengao.) Li Gui, upon hearing Emperor Gaozu's offer, indicated that he was inclined to accept – as he saw Emperor Gaozu as a cousin, and that he should then accept the Tang-bestowed title of Prince of Liang. Cao disagreed, suggesting that he should not prostrate himself to Tang, but rather, if he wanted to submit, he should use the model Emperor Xuan of Western Liang used when submitting to Northern Zhou – continuing to use imperial title, but at the same time declaring himself a subject. Li Gui agreed, and he sent his official Deng Xiao () to Chang'an, and he, while declaring submission to Emperor Gaozu, used for himself the title of, "Your subject and younger imperial cousin, Li Gui the Emperor of Liang." Emperor Gaozu was displeased and detained Deng, and he began to discuss an attack on Li Gui. He sent messengers to enter into a peace treaty with Tuyuhun's Busabuo Khan, Murong Fuyun, offering to return Murong Fuyun's son Murong Shun (who had been detained by Sui). Murong Fuyun was pleased, and attacked Liang as per Tang instructions, to weaken Li Gui.