During Later Jin's establishment

As of 936, Later Tang was embroiled in internal strife, as then-emperor Li Congke was suspicious that his brother-in-law Shi Jingtang the military governor (Jiedushi) of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi), would rebel against him. At the advice of the imperial scholars Li Song and Lü Qi (呂琦), Li Congke considered entering an alliance with the Khitan to ward off the possibility that Shi would seek aid from Khitan. However, when another imperial scholar, Xue Wenyu (薛文遇), argued against it by predicting that Emperor Taizong would demand a marriage alliance, Li Congke changed his mind and never made the alliance proposal.^[7]

Not long after, in summer 936, Li Congke, under Xue's suggestion, issued an edict moving Shi from Hedong to Tianping Circuit (天平, headquartered in modern Tai'an, Shandong). This caused Shi to fear that he would be executed if he left Hedong, and so he rebelled. With Li Congke then sending an army, commanded by Zhang Jingda, to attack Hedong, Shi sent emissaries to Khitan to request aid, promising that, if Emperor Taizong would support him as the emperor of China, to serve Emperor Taizong as a father and to cede Lulong Circuit (盧龍, headquartered in modern Beijing) and Hedong's prefectures north of the Yanmen Pass to Khitan. When Shi's emissaries arrived at the Khitan court, Emperor Taizong was pleased, and he stated to Empress Dowager Shulü, "Your son had dreamt that Master Shi would be sending messengers here. Now it has happened. This was the will of heaven." He sent a reply that he would lead his entire empire's forces to aid Shi in the fall.^[7]

Meanwhile, Zhang put Hedong's capital Taiyuan under siege. Taiyuan was running low on food supplies, but its defenses held. In late fall, Emperor Taizong himself commanded 50,000 cavalry soldiers (but claimed publicly that it was 300,000) and headed for Taiyuan. When he arrived at Taiyuan's outskirts, Shi urged caution and not immediate engagement, but Emperor Taizong did not listen. Rather, he engaged Zhang's army immediately, crushing it and lifting the siege on Taiyuan. The remnants of Zhang's army took up position at Jin'an Base (晉安寨), near Taiyuan, but the combined Khitan/Hedong forces then put it under siege. While continuing to siege the Later Tang forces at Jin'an, Emperor Taizong created Shi emperor, having his state known as Jin (referred to by later historians as Later Jin. As part of Shi's enthronement announcement, he announced the agreement to cede Lulong and parts of Hedong, for a total of 16 prefectures, to Khitan, as well as to submit a large amount of silk each year as tribute.^[7]

Li Congke ordered Zhao Dejun the military governor of Lulong to command another army to rescue Zhang at Jin'an, but Zhao himself wanted Emperor Taizong's support to be emperor of China, and therefore halted some distance away at Tuanbo Valley (團柏谷, in modern Jinzhong, Shanxi), while he sent secret emissaries to Emperor Taizong's camp, negotiating with him. Zhao, who submitted bribes of gold and silk to Emperor Taizong, promised the terms of being fraternal states with Khitan and that Shi would be allowed to retain Hedong. As Zhao's army was still a strong one, Emperor Taizong was enticed. Shi, hearing of this, sent his close advisor Sang Weihan to plead with Emperor Taizong, arguing that the Khitan/Later Jin forces would prevail and that he should not turn his back on Shi. Emperor Taizong, after consideration, agreed with Sang and rejected Zhao's overture.^[7]

After Jin'an had been under siege for three months and ran out of supplies, Zhang's deputy Yang Guangyuan assassinated Zhang and surrendered the remaining Later Tang army, which Emperor Taizong turned over to Shi. Then they began to march toward the Later Tang capital Luoyang. With Yang having surrendered, Zhao's army lost its morale and also collapsed, and Zhao surrendered. At that time, Li Congke, who had himself led another Later Tang relief force northward, decided to return to Luoyang, but once he returned to Luoyang saw that the morale was crumbling and that many more generals were already surrendering to the combined Khitan/Later Jin forces. Emperor Taizong escorted Shi to Lu Prefecture (潞州, in modern Changzhi, Shanxi), and then, citing his belief that the Han Chinese would panic if Khitan forces actually arrived at Luoyang, stayed at Lu while Shi approached Luoyang. Li Congke, finding the situation hopeless, committed suicide with his family. Prior to the suicide, he had Emperor Taizong's older brother Yelü Bei executed. Shi entered Luoyang and established his authority there. He had Yelü Bei's casket escorted with honor back to Khitan.^[7]

After Later Jin's takeover of central China

Emperor Taizong returned to Khitan proper with a number of Later Tang generals that he had detained.^[1] He also established Lulong's capital You Prefecture (幽州) as the southern capital, to facilitate the governance of the newly received 16 prefectures. He respected the captured official Zhang Li and listened to much of Zhang's advice.^[8]

In 937, Xu Gao, the regent of Later Jin's southeastern neighbor Wu sent an emissary to Khitan to try to establish friendly relations. Emperor Taizong also sent an emissary to Wu in return. Later in the year, Emperor Taizong changed the name of his state from Khitan to Liao. He modeled his government after Chinese states', and made Zhao Dejun's son Zhao Yanshou a chief of staff (Shumishi) and chancellor. Later, after Xu seized the Wu throne and established Southern Tang as its emperor, he continued friendly relations with Liao, but on one occasion decided to assassinate the Liao emissary once the Liao emissary crossed into Later Jin territory, hoping to blame Later Jin for the assassination and disrupt Liao and Later Jin relations.^[8]

Meanwhile, Shi Jingtang, as Later Jin's emperor, continued to be very submissive to Liao. In 938, he offered honorific titles to Emperor Taizong and Empress Dowager Shulü, and sent his senior officials Feng Dao and Liu Xu to the Liao court to officially present the titles. During Shi's reign as Later Jin's emperor, he referred to himself as "subject" and "son," while referring to Emperor Taizong as "father emperor." Whenever Emperor Taizong issued edicts to him, he would receive them in a side hall rather than his own imperial hall, to show respect. Whenever at the Liao emperor's and empress dowager's birthdays or the deaths of key Liao officials, he would often present gifts, including also to Empress Dowager Shulü, Yelü Lihu, Yelü Anduan, the two chancellors in charge of Liao's southern and northern branches of government, and key Han officials such as Zhao Yanshou and Han Yanhui. Further, even when Emperor Taizong sent arrogantly-worded edicts, Shi would respond meekly. Therefore, throughout Shi's reign, there would be no disputes between Liao and Later Jin.^[8]

In late 938, Shi, fearing that Yang Guangyuan, then the military governor of Tianxiong Circuit (天雄, headquartered in modern Handan, Hebei), would be difficult to control, and therefore divided Tianxiong and moved Yang to be the military governor of Heyang Circuit (河陽, headquartered in modern Luoyang, Henan) and the defender of Luoyang. It was said that after this movement, Yang began to be resentful of the Later Jin imperial government and entered into secret communications with the Liao court.^[8]

In 939, fearing that An Chongrong the military governor of Chengde Circuit (成德, headquartered in modern Shijiazhuang, Hebei) would rebel, Shi moved An's potential ally Huangfu Yu (皇甫遇) the military governor of the neighboring Yiwu Circuit (義武, headquartered in modern Baoding, Hebei) to Zhaoyi Circuit (昭義, headquartered at Lu Prefecture). Emperor Taizong tried to use this opportunity to inject himself into the commissioning of Yiwu's military governor, proposing that the Liao official Wang Wei (王威), whose father Wang Chuzhi had previously ruled Yiwu in alliance with Later Tang's predecessor state Jin, be made Yiwu's military governor. When Shi refused (based on the rationale that Wang needed to go through several layers of promotions to qualify (from prefect to military prefect to defender to military governor), Emperor Taizong sent back the angry response of, "How many layers of promotion did you go through from being military governor to be the Son of Heaven?" Shi, in fear, sent a rich tribute and promised to make Wang Chuzhi's grandnephew Wang Tingyin (王廷胤) Yiwu's military governor. That somewhat placated Emperor Taizong.^[9]

An Chongrong, in addition to considering a rebellion against Later Jin, was particularly hostile to Liao. Whenever Liao emissaries passed through Chengde, he would curse them and sometimes even kill them. In 940, he seized a Liao emissary, and then submitted an arrogantly-worded petition to Shi, demanding that he terminate his submissiveness to Liao and turn against Liao for its mistreatment of the Chinese people. Sang secretly pointed out to Shi that turning against Liao could not yield any benefit — and, in his evaluation of Emperor Taizong, referred to Emperor Taizong as being "more intelligent and brave than other people." Shi listened to Sang, and instead tried to persuade An against provocative behaviors against Liao. He also sent Yang Yanxun (楊彥詢) the military governor of Anguo Circuit (安國, headquartered in modern Xingtai, Hebei) as an emissary to Liao, to explain to Emperor Taizong, who was angry over An's killing of Liao emissaries, to explain that An's provocative behavior did not reflect a chance in Later Jin's overall submission.^[9]

In winter 941, An Chongrong's ally, An Congjin the military governor of Shannan East Circuit (山南東道, headquartered in modern Xiangyang, Hubei) rebelled against Later Jin. Shortly after, An Chongrong, hearing of An Congjin's rise, also did so. The Later Jin army against An Chongrong, commanded by Shi's brother-in-law Du Chongwei, quickly defeated An Chongrong, and An Chongrong was killed by his own officers. Shi had An Chongrong's head delivered to Liao. (An Congjin, however, would not be destroyed until shortly after Shi's own death.)^[10]

Despite An Chongrong's defeat, Emperor Taizong continued to send emissaries to Later Jin, rebuking Shi for the fact that Tuyuhun tribesmen, whose grazing lands were part of the territory ceded by Later Jin to Liao, were often defecting from Liao back to Later Jin. It was said that this caused Shi much fear and caused him to fall ill. In summer 942, he died. After a discussion between Feng Dao and the Later Jin imperial guard general Jing Yanguang, they decided that the state needed an older emperor, so instead of supporting Shi's youngest and only surviving son Shi Chongrui (石重睿) as Later Jin's emperor, they supported his adoptive son and biological nephew Shi Chonggui, who was an adult, as Later Jin's emperor.^[10]

Initial deterioration of relations

Shortly after Shi Chonggui's succession to the Later Jin throne, the tone of the Liao-Later Jin relationship began to change, as Shi Chonggui, at Jing Yanguang's advice and against Li Song's, did not submit a petition but rather sent a letter to the Liao court to announce his succession, essentially declaring the states equal. Moreover, in the letter, he did not refer to himself as "subject" but only as "grandson." This caused Emperor Taizong to be angry and respond, "How do you dare not to first report to me before taking the throne?" Jing authored an insolent response on Shi's behalf. Thereafter, Zhao Yanshou, who was then Liao's military governor of Lulong, began to advocate that Emperor Taizong attack Later Jin, hoping that Emperor Taizong would replace Shi with Zhao himself. Emperor Taizong began to be enticed.^[10]

Meanwhile, Jing upped the hostility by arresting Qiao Rong (喬榮), the Liao commerce officer stationed at Later Jin's capital Kaifeng, and seizing Liao's commercial assets. Further, the Liao merchants were arrested and killed. When Qiao was released later in the year and allowed to return to Liao, Jing gave him an arrogant speech:^[10]

Tell your master: the deceased emperor [(i.e., Shi Jingtang)] was placed in his position by the northern dynasty [(i.e., Liao)], and that is why he claimed himself to be a subject and submitted reports. The current emperor was placed in his position by China itself. The only reason why he subordinated himself to the northern dynasty is that he did not forget the alliance the deceased emperor entered. It was enough for him to claim himself to be a grandson; there is no reason for him to claim himself to be a subject. The emperor of the northern dynasty should not be deluded by Zhao Yanshou such that he insults China. You have seen the soldiers and horses that China possesses. If the grandfather is angry, he can come and battle us. The grandson has 100,000 sharpened swords waiting for him. If he were defeated by his grandson, he would become the laughing stock of the entire world. Do not forget this!

As Qiao feared that Emperor Taizong would blame him for the loss of the Liao wealth, he flattered Jing and requested that Jing write his words down on paper. Jing had his secretary write down the words and give them to Qiao. When Qiao presented them to Emperor Taizong, Emperor Taizong was incensed, and therefore became resolute that he would attack Later Jin. He had the Later Jin emissaries detained at You Prefecture and refused to see them himself. Even though Sang Weihan repeatedly suggested that Shi Chonggui revert to subservience to Liao to avoid a war, Jing repeatedly stopped Shi from doing so.^[10]

By winter 943, Yang Guangyuan, who was then Later Jin's military governor of Pinglu Circuit (平盧, headquartered in modern Weifang, Shandong), was in a mutually-suspicious relationship with the Later Jin imperial government, and, while he had not yet rebelled, was in communication with Emperor Taizong, urging him to attack Later Jin due to Shi's defiant behavior. Emperor Taizong thereafter gave Zhao 50,000 soldiers from Lulong and Datong (大同, headquartered in modern Datong, Shanxi) Circuits, asking him to manage the campaign to capture central China, stating to him, "If you gained it, I will make you emperor." He also often stated to the Han people in pointing to Zhao, "This is your Lord."^[10]

Liao incursions into Later Jin territory

In spring 944, Emperor Taizong made a major incursion into Later Jin territory, using Zhao Yanshou and Zhao Yanzhao (趙延照) as his forward commanders. The Liao forces first captured Bei Prefecture (貝州, in modern Xingtai, Hebei), and then grouped near Yedu (鄴都, capital of the former Tianxiong Circuit). Shi Chonggui tried to respond diplomatically, but his emissaries could not get through the Liao army and reach Emperor Taizong to deliver his letters. He also sent a number of generals to respond, with Jing Yanguang in effective command of the overall operations, but also himself went to the frontline. The second Liao thrust, led by Yelü Andu toward Hedong, however, was repelled by Hedong's military governor Liu Zhiyuan. Later Jin's prefect of Bo Prefecture (博州, in modern Liaocheng, Shandong), Zhou Ru (周儒), who was in secret communications with Yang Guangyuan, surrendered Bo to Liao forces, and encouraged them to cross the Yellow River at Majiakou (馬家口, in modern Liaocheng), to join forces with Yang. Jing was convinced by Yan Kan (顏衎) the acting military governor of Tianping that if Liao forces were able to cross the river, disaster would ensue,^[10] so the Later Jin imperial forces concentrated on battling Liao forces at Majiakou to prevent them from successfully crossing, and were able to do so. In anger, Liao forces slaughtered Han civilians that they had captured, which led to fiercer resistance from the populace. Later in spring 944, the armies commanded by the two emperors confronted each other near Yedu, but did not engage each other. Eventually, the Liao forces withdrew, pillaging as it went along over Later Jin's territory north of the Yellow River. Yang led his own troops west from Pinglu's capital Qing Prefecture (青州), and tried to meet the Liao forces at the Yellow River, but by the time he reached there, Liao forces had already left. Shi then sent the imperial guard general Li Shouzhen to attack Yang, and in winter 944, Yang's son Yang Chengxun (楊承勳) put his father under house arrest and surrendered. (Yang Guangyuan was later secretly killed on Shi's orders.)^[11]

In winter 944, Emperor Taizong again made a major incursion into Later Jin territory, using Zhao Yanshou as his forward commander. Shi was initially going to lead the Later Jin army himself, but fell ill at that time. He sent a number of generals to try to cut off the Liao army movement, but then, in fear of the Liao army's strengths, pulled back to the Yedu region, allowing the Liao army to advance unimpeded to Yedu, pillaging the Later Jin territory as it went along. However, the Liao army then withdrew in spring 945. As the Liao army withdrew, Shi sent Du Wei (i.e., Du Chongwei, who changed his name to observe naming taboo for Shi) and Li in command of an army to give chase. They crossed into Liao territory and captured Qi (祁州) and Tai (泰州) (both in modern Baoding), but soon received news that the Liao army had turned around and was heading for them. They tried to withdraw, but became surrounded near Yangcheng (陽城, in modern Baoding). Du panicked and was reluctant to engage the Liao army, but at Fu Yanqing's advocacy, Fu, Zhang Yanze, Yao Yuanfu (藥元福), and Huangfu Yu (皇甫遇), attacked the Liao army fiercely, causing the Liao army to panic and flee. After Emperor Taizong was able to regroup at You, he caned each of the chieftains who were part of the operation several hundred times, with only Zhao Yanshou escaping punishment.^[11]

It was described that, by this point, the incessant Liao incursions were rendering Later Jin's imperial army fatigued and its border regions desolate. Liao itself had also suffered many casualties to its soldiers and animals, and the Khitan people tired of the campaigns. Empress Dowager Shulü tried to urge Emperor Taizong into a more conciliatory posture with Later Jin. Meanwhile, Sang Weihan, who had taken over much of the military responsibility from Jing by this point, also was urging Shi to take a reconciliatory approach. In summer 945, Shi sent the emissary Zhang Hui (張暉) to the Liao court, apologizing and begging forgiveness. Emperor Taizong responded, "Send Sang Weihan and Jing Yanguang to come see us, and cede the two circuits of Zhen (鎮州, i.e., Chengde, as Zhen was the capital of Chengde, now renamed Shunguo (順國)) and Ding (定州, i.e., Yiwu, as Ding was the capital of Yiwu) to us, then there will be peace." Shi found the response insulting, and cut off further communications.^[11] He considered an alliance with Goryeo's King Taejo against Liao, but then found out that Goryeo lacked the strength to attack Liao, and so abandoned the idea.^[12]

Liao's destruction of Later Jin

In 946, there were rumors that Zhao Yanshou was planning on defecting to Later Jin. This rumor was believed by the Later Jin chiefs of staff Li Song and Feng Yu. They had Du Wei write a letter to Zhao, encouraging him to do so, with the officer Zhao Xingshi (趙行實), who had previously served under Zhao Yanshou, delivering the letter. Zhao Yanshou wrote back (to try to lead Later Jin forces into a trap), stating, "I have long been in a foreign land, and I want to return to China. Please launch a major army to support me, so that I can pull myself out and return with it." Subsequently, under Emperor Taizong's orders, Liao's prefect of Ying Prefecture (瀛州, in modern Cangzhou, Hebei), Liu Yanzuo (劉延祚), also offered to defect to Later Jin. Shi thus put Du and Li Shouzhen in command of an army to attack north, with the stated objectives being to first recapture the prefectures previously ceded to Liao, and then to destroy Liao. When Du and Li advanced, though, they were met by a large army that Emperor Taizong personally commanded. The Liao army eventually surrounded the Later Jin army at Zhongdu Bridge (中度橋, in modern Baoding). After Emperor Taizong made the promise to Du to make him emperor if he surrendered, Du and Li surrendered their army. Emperor Taizong had Zhao comfort the Later Jin soldiers and told him that the Later Jin army was now his, and then prepared to advance south. With virtually the entire Later Jin army having been given to Du and Li for this northern campaign, then-Later Jin capital Daliang was left essentially defenseless, and Shi Chonggui felt compelled to surrender, ending Later Jin. Emperor Taizong subsequently entered Daliang.^[12]