Prince of Jin
The last Tang emperor, Emperor Ai, was forced to yield the throne to the major warlord (and Li Keyong's archrival) Zhu Quanzhong the military governor of Xuanwu Circuit (宣武, headquartered in modern Kaifeng, Henan) in 907, and Zhu declared himself emperor of a new Later Liang (as its Emperor Taizu). Li Keyong and several other major warlords (Li Maozhen, Wang Jian, and Yang Wo) refused to recognize the new Later Liang state, and effectively became rulers of their own states (in Li Keyong's case, Jin, as he carried the Tang-bestowed title of Prince of Jin). In 908, Li Keyong died and was succeeded as the Prince of Jin by his son Li Cunxu. Guo continued to serve Li Cunxu, and it was said that Li Cunxu valued his service.