李嗣源
In 912, Li Cunxu launched a major campaign, intending to destroy the Yan state ruled by Liu Shouguang, with Zhou in command of the overall operations. As part of the campaign, Li Siyuan was in charge of attacking Ying Prefecture (瀛州, in modern Cangzhou, Hebei), and he was successful in getting its prefect, Zhao Jing (趙敬), to surrender. Subsequently, when Liu sent his major general Yuan Xingqin to his northern borders with the Khitan Empire to await potential aid from Khitan's Emperor Taizu, Li Cunxu sent Li Siyuan to intercept Yuan's army. Li Siyuan first attacked Wu Prefecture (武州, in modern Zhangjiakou, Hebei), and its prefect Gao Xinggui (高行珪) surrendered. Yuan then attacked Wu Prefecture, and when Li Siyuan came to its aid, Yuan tried to withdraw, but Li Siyuan subsequently engaged him eight times and forced him into surrendering. Li Siyuan took Yuan as an adoptive son and kept Yuan under his command. (Gao Xinggui's brother Gao Xingzhou, whom Gao Xinggui sent to seek aid from Li Siyuan, also joined Li Siyuan's army and subsequently often commanded Li Siyuan's guards along with Li Siyuan's adoptive son Li Congke – the son of Li Siyuan's concubine Lady Wei.) Jin forces were subsequently able to destroy Yan and add its territory to Jin. (In 915, when Li Cunxu heard of Yuan's ferocity in battle, he requested that Li Siyuan send Yuan to serve under his own personal army, and Li Siyuan, unwilling to resist the order, reluctantly sent Yuan to Li Cunxu. Li Cunxu also wanted Gao Xingzhou and tried to entice Gao with promotion offers, but Gao declined to leave Li Siyuan's command.)