Liu Zhijun (Chinese: 劉知俊; died January 21, 918?), courtesy name Xixian (希賢), nicknamed Liu Kaidao (劉開道, "Liu who opened the way"), was a general under Zhu Wen (Zhu Quanzhong) while Emperor Taizu was a major warlord during the late Tang dynasty and then during Emperor Taizu's reign in his new Later Liang. Later, fearing that Emperor Taizu was going to act against him, he defected, first to Qi, then to Former Shu. Former Shu's emperor Wang Jian (Emperor Gaozu), however, also was apprehensive of his talent and later had him executed.
It is not known when Liu Zhijun was born, but it is known that he was from Pei County. It was said that he had a handsome appearance and had great ambitions. He initially served under Shi Pu the military governor (Jiedushi) of Ganhua Circuit (感化, headquartered in modern Xuzhou, Jiangsu), and was highly regarded by Shi. However, his bravery and good use of tactics eventually caused Shi to be apprehensive of him. Around the new year 892, he submitted to Zhu Quanzhong the military governor of Xuanwu Circuit (宣武, headquartered in modern Kaifeng, Henan), who was then engaged in a lengthy campaign against Shi. It was said that Liu's surrender to Zhu was a big blow to the Ganhua army, which from that point on was no longer able to stand up against Xuanwu. (Ganhua's capital Xu Prefecture (徐州) would eventually fall to Zhu's army in 893, and Shi committed suicide.) Zhu put the two Yisheng armies (義勝軍) under Liu's command, and made him "Kaidao Commander" (開道指揮使, "the commander who opens the way"), thus leading to Liu's receiving the nickname of "Liu Kaidao." He later successively served as the prefect of Hai Prefecture (海州, in modern Lianyungang, Jiangsu), Huai Prefecture (懷州, in modern Jiaozuo, Henan), and Zheng Prefecture (鄭州, in modern Zhengzhou, Henan).
In 901, the powerful eunuchs, led by Han Quanhui, feared that then-reigning Emperor Zhaozong and the chancellor Cui Yin were about to slaughter them. They therefore seized Emperor Zhaozong and took him from the capital Chang'an to Fengxiang Circuit (鳳翔, headquartered in modern Baoji, Shaanxi), then ruled by the eunuchs' ally Li Maozhen. Cui summoned Zhu, who subsequently put Fengxiang's capital Fengxiang Municipality under siege. However, the siege stalled, and Zhu was unable to capture Fengxiang for a long duration. As of fall 902, with his army facing rains and the accompanying illnesses, Zhu was considering lifting the siege and withdrawing to Hezhong (河中, in modern Yuncheng, Shanxi). Only at the urging by Liu and Gao Jichang did Zhu maintain the siege. (Subsequently, at Gao's suggestion, Zhu had a soldier surrender to Li and falsely claim that the Xuanwu forces were withdrawing. Li came out of Fengxiang and tried to attack Zhu's "withdrawing" army, and was trapped; he was only able to get back into Fengxiang with heavy losses. Li eventually slaughtered the eunuchs and surrendered the emperor to Zhu in spring 903 to sue for peace.)
In spring 904, after Zhu had Cui killed (after suspecting Cui of turning against him), he further forced Emperor Zhaozong to move the capital from Chang'an to Luoyang. In the aftermaths, Zhu made Han Jian the military governor of Youguo Circuit (佑國, headquartered at Chang'an) and Liu the military governor of Kuangguo Circuit (匡國, headquartered in modern Weinan, Shaanxi), to defend against potential attacks from Li Maozhen and Li Maozhen's adoptive son Li Jihui the military governor of Jingnan Circuit (靜難, headquartered in modern Xianyang, Shaanxi). In 906, when Li Jihui, along with the forces of Fengxiang and three other circuits then under Li Maozhen's control — Baosai (保塞, headquartered in modern Yan'an, Shaanxi), Zhangyi (彰義, headquartered in modern Pingliang, Gansu), and Baoda (保大, headquartered in modern Yan'an as well) — attacked Dingnan Circuit (定難, headquartered in modern Yulin, Shaanxi), Dingnan sought aid from Zhu. Zhu ordered Liu and Kang Huaizhen (康懷貞) to aid Dingnan. Liu first attacked Baoda, capturing Liu Yanhui (劉彥暉) the prefect of Baoda's Fang Prefecture (坊州, in modern Yan'an), and then defeated Li Jihui at Meiyuan (美原, in modern Weinan), forcing Li Jihui to withdraw back to Jingnan's capital Bin Prefecture (邠州). Liu Zhijun and Kang then attacked and captured Baoda's capital Fu Prefecture (鄜州) and Baosai's capital Yan Prefecture (延州), as well as three other prefectures. It was said that this was a huge blow to Li Maozhen's army. Liu was rewarded with the honorary chancellor designation of Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事), while Kang was made the military governor of Baoda.
In 907, Zhu Quanzhong had Emperor Zhaozong's son and successor Emperor Ai yield the throne to him, ending the Tang dynasty and starting a new Later Liang with him as its Emperor Taizu. A number of regional warlords refused to recognize him as their emperor and whose domains effectively became independent states — including Li Maozhen (whose state became known as Qi as his title was Prince of Qi), Li Keyong the military governor of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi) (whose state became known as Jin as his title was Prince of Jin), Yang Wo the military governor of Huainan Circuit (淮南, headquartered in modern Yangzhou, Jiangsu) (whose title was Prince of Hongnong but whose state was also known as Wu as his father and predecessor Yang Xingmi was the Prince of Wu) and Wang Jian (whose state became known as Former Shu as his title was Prince of Shu and he soon thereafter claimed the title of emperor himself).
One of the campaigns the new Later Liang emperor launched thereafter was an attack against Jin's Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), which was then governed by Li Keyong's adoptive nephew Li Sizhao. Later Liang forces put Zhaoyi's capital Lu Prefecture (潞州) under siege, and Li Keyong, who was seriously ill, was initially unable to dispatch a relief force. (Li Keyong would die shortly after and be succeeded by his son Li Cunxu.) Still, in spring 908, with the Liang commander Li Si'an (李思安) unable to capture Lu Prefecture, Emperor Taizu went to the frontline himself to oversee the siege, while also summoning Liu from Kuangguo (which, shortly after, Emperor Taizu renamed Zhongwu (忠武), swapping the name with the circuit headquartered in modern Xuchang, Henan) to command the forces involved in the Lu operation. Liu had initial successes against Jin forces and requested to stay to finish the siege, but Emperor Taizu was concerned that Qi forces might attack Zhongwu, so he had Liu head over to Jin Prefecture (晉州, in modern Linfen, Shanxi) to stay there and gradually return to Zhongwu. Soon thereafter, a surprise attack by Li Cunxu and his general Zhou Dewei defeated the Later Liang troops sieging Lu Prefecture, and, in the aftermaths of the victory, Zhou tried to take Ze Prefecture (澤州, in modern Jincheng, Shanxi) as well. The Later Liang general Niu Cunjie (牛存節) held out, and Liu dispatched his own forces from Jin Prefecture to aid Niu, causing Zhou to abandon the attack on Ze and withdraw.
In fall 908, Former Shu and Qi forces attacked Chang'an, and Jin forces under Zhang Chengye were also set to join the battle. Liu and Wang Chongshi (王重師) the military governor of Youguo Circuit (who had replaced Han Jian), however, defeated Qi forces at Mu Valley (幕谷, in modern Xianyang), and the Former Shu and Jin forces also thereafter withdrew. Shortly after, the Qi military governor of Baosai, Hu Jingzhang (胡敬璋), attacked Shangping Pass (上平關, in modern Lüliang, Shanxi), but was repelled by Liu. (This incident implied that Liu's and Kang Huaizhen's capture of Yan Prefecture in 904 did not permanently hold the prefecture for Later Liang at that point.)
Late in 908, Hu died and was succeeded by Liu Wanzi (劉萬子), who, however, was cruel and unpopular, and Li Jihui also thought that Liu Wanzi was in communications with Later Liang. He therefore had the officer Li Yanshi (李延實) assassinate Liu Wanzi and take over Baosai. In response, Liu Wanzi's officer Gao Wanxing (高萬興) and his brother Gao Wanjin (高萬金) surrendered to Liu Zhijun. Shortly after, Liu Zhijun put Yan Prefecture under siege himself and sent Liu Ru (劉儒) to siege Fang Prefecture. Li Yanshi then surrendered to Liu Zhijun, while Qi's military governor of Baoda, Li Yanbo (李彥博), and Li Yanyu (李彥昱) the prefect of Fang Prefecture abandoned their posts and fled back to Fengxiang. Emperor Taizu commissioned Gao Wanxing as the military governor of Baosai and Niu as the military governor of Baoda, while ordering Liu to try to further conquer Jingnan Circuit. Liu believed that it would be difficult to do so, so he declined by stating that his food supplies were not sufficient, so Emperor Taizu let him return to Zhongwu.