[1] The first reference to him in historical sources was in 903, at which time he was serving under Ma Yin, who was the military governor of Wu'an Circuit (武安, headquartered in modern Changsha, Hunan) and already described as a general.
[2] Later in 903, when Cheng Rui the military governor of Jingnan Circuit (荊南, headquartered in modern Jingzhou, Hubei) was, at Zhu's request, leading an army down the Yangtze River to try to save Du Hong the military governor of Wuchang Circuit (武昌, headquartered in modern Wuhan, Hubei), who was then under siege by Yang's general Li Shenfu, Ma sent Xu to launch a joint surprise attack on Jingnan's capital Jiangling Municipality, with Ouyang Si (歐陽思), an officer under Lei Yanwei the military governor of Wuzhen Circuit (武貞, headquartered in modern Changde, Hunan).
At that time, Ma was sending Qin to attack Wuzhen in conjunction with Ni Kefu (倪可福), an officer sent by Gao Jichang the Later Liang military governor of Jingnan.
Yang Wo sent the Ling Ye (泠業) and Li Rao (李饒) to try to save Lei Yangong, but Xu laid a trap for them on the way and captured them.
)[4] Meanwhile, after the joint action, Gao stationed forces at Hankou (漢口, in modern Wuhan) and blocked off Ma's tributary communication route with Later Liang.
However, in 911, Liu Yan the military governor of Qinghai Circuit (清海, headquartered in Guangzhou, Guangdong) attacked Ningyuan.
[6] Xu later returned to Yue Prefecture, as he was described as the prefect of Yue during an operation in 914 when the Chu officer Wang Huan (王環) launched a surprise attack against Huang Prefecture (黃州, in modern Wuhan) — a part of Wuchang, ruled by Hongnong, whose state name had been changed to Wu by this point.
[9] Later in 928, Wu launched a major attack on Yue Prefecture, commanded by Miao Lin (苗璘) and Wang Yanzhang (王彥章).
When sending them off at a feast, Xu, who had by this point had become concerned that Ma's sons were fighting over succession rights, made what was later viewed as a prophetic statement:[9] While Chu is small, its senior officials and generals are still present.
For you to consider attacking us, you have to wait until the ponies [(i.e., Ma's sons, with Xu employing a double entendre given that "Ma" meant "horse")] are fighting over the stable.Meanwhile, Gao, after breaking with Li Siyuan, submitted to Wu, and the Wu emperor Yang Pu (Yang Longyan's brother and successor) created Gao the Prince of Qin.