李罕之
It is not known when Yang Shihou was born, but it is known that he was from Jingou (斤溝, in modern Fuyang, Anhui). In his youth, he served as a soldier under Li Hanzhi, who was then the military governor ("Jiedushi") of Heyang Circuit (河陽, headquartered in modern Jiaozuo, Henan). After Li Hanzhi lost his own territory and became a subordinate of Li Keyong the military governor of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi) in 888, Li Hanzhi gave, as a tribute to Li Keyong, about 100 elite soldiers, and Yang was one of the soldiers thus sent to join the Hedong army. However, Yang did not distinguish himself while serving under Li Keyong. Later, after he was accused of crimes, he fled to Li Keyong's archenemy Zhu Quanzhong the military governor of Xuanwu Circuit (宣武, headquartered in modern Kaifeng, Henan). Zhu made him an officer in the Xuanwu army and the prefect of Cao Prefecture (曹州, in modern Heze, Shandong).