In his youth, he came to serve under the warlord Liu Shouguang, who controlled the region and who would later declare himself the emperor of a state of Yan, as a general of the cavalry.
When they reached Qigo Pass (祁溝關, in modern Baoding, Hebei), the officer Gong Yanzhang (宮彥璋) persuaded the soldiers to mutiny, and they killed Li Cunju.
Lu then attacked Wu Prefecture (武州, in modern Zhangjiakou), but was repelled by the general Li Sigong (李嗣肱).
[4] Soon thereafter, with Lu Wenjin as their guide, the Khitan army launched a major attack on Jin's northern borders, quickly capturing Xin Prefecture.
Emperor Taizu thereafter gave Lu the title of military governor of Lulong as well, stationing him and his ethnic Han soldiers at Ping Prefecture (平州, in modern Qinhuangdao, Hebei).
When Li Cunxu thereafter did, as anticipated, announce a general campaign against Zhang, Emperor Taizu launched a major attack south.
However, when Li Cunxu himself engaged the Khitan army in spring 922 and defeated them, Emperor Taizu, stating to Lu, "Heaven did not intend for me to come here," and withdrew.
Later in the year, with the Khitan army repelled, Chengde's capital Zhen Prefecture (鎮州, in modern Shijiazhuang, Hebei), fell.
Zhu committed suicide as Daliang fell, ending Later Liang and allowing Li Cunxu to take over its territory as the emperor of a new Later Tang.
Lu's own soldiers, predominantly Han, wanted him to do so, and he thereafter killed the commander of the Khitan garrison (sent to assist him) and took his army (described to be about 100,000 men in strength with 8,000 wagons) to You Prefecture to submit to Later Tang.
Li Siyuan made him the military governor of Yicheng Circuit (義成, headquartered in modern Anyang, Henan) and gave him the honorary chancellor title of Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事).
Yet later in Li Siyuan's reign (during the Changxing era (930-933)), he was made the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi).