In 922, Li Cunxu claimed the title of emperor of a new state of
Later Tang. However, at that time, Later Tang was facing military pressure both from Later Liang and Khitan, and the military food supply and morale were low. At that time, the main Later Liang army was commanded by
Dai Siyuan, who also served as the military governor of Tianping Circuit (天平, headquartered in modern
Tai'an,
Shandong). He left his officers Lu Shunmi (), Liu Suiyan (), and Yan Yong () at Tianping's capital Yun Prefecture () to defend it. Shortly after Li Cunxu's declaration of imperial title, however, Lu defected to Later Tang and revealed that Yun was defended by less than 1,000 soldiers and that Liu and Yan lacked support from the soldiers. He advocated that Later Tang attack it by surprise. As Yun was deep in Later Liang territory south of the Yellow River, however, most of Li Cunxu's generals, including his chief of staff (
Shumishi)
Guo Chongtao, opposed Lu's proposal, believing that it would be dangerous and futile. Li Siyuan, however, wanting to repair his relationship with Li Cunxu, offered to command this mission by himself. Li Cunxu agreed, and allowed him to take 5,000 soldiers to, under cover of darkness, rapidly descend on Yun to attack it. Li Siyuan's army managed to evade Later Liang detection, and when they reached Yun, Li Congke led the soldiers in scaling the walls. The city fell to Li Siyuan, who was commissioned the military governor of Tianping and held it for Later Tang over the next several months as the Later Liang army (by then under the command of
Wang Yanzhang) futilely tried to cut off the supply route from Later Tang proper to Yun. Later Liang's emperor
Zhu Zhen then decided to replace Wang with
Duan Ning. Duan crossed the Yellow River and headed for Chan Prefecture (澶州, in modern
Anyang,
Henan) and prepared an ambitious four-prong attack against Later Tang: (Apparently it was around this time that, on an occasion when Li Congke was at Zhen Prefecture – which served as the capital of Chengde Circuit (), which his father Li Siyuan was the military governor of – LI Congke and Li Siyuan's close associate
An Chonghui got into a dispute at dinner. Li Congke punched An hard in the head, and An only avoided further injury by fleeing. Li Congke later regretted and apologized, but while An accepted the apology, he bore a grudge against Li Congke from that point on.) Before he could reach there, though, Li Cunxu was killed in a mutiny at Luoyang itself. Li Siyuan entered Luoyang and took the title of regent, as he was apparently undecided at that time whether to support Li Cunxu's son
Li Jiji the Prince of Wei, who was returning from an expedition that destroyed Later Tang's southwestern neighbor
Former Shu. == During Li Siyuan's reign ==