The four former Yan generals formed alliances among themselves, as well as with two other military governors,
Li Zhengji and
Liang Chongyi, hoping to be able to pass their territories to their descendants, semi-independent of the Tang imperial government, retaining their armies and taxes without submitting them to the imperial government. As part of this alliance, Li Baochen's brother Li Baozheng () married Tian's daughter, and Li Baochen gave a daughter in marriage to Li Zhengji's son
Li Na and took a daughter of Li Zhengji's to be the wife of his son Li Weicheng (). Li Baochen, however, would for a while be more submissive to the imperial government than others in the alliance, and when
Zhu Xicai assassinated Li Huaixian in 768 and took over Lulong Circuit (盧龍, i.e., the circuit formerly known as Fanyang), Li Baochen attacked Zhu Xicai under the name of the Tang imperial regime, but he was repelled by Zhu, and Emperor Daizong subsequently allowed Zhu to retain Lulong Circuit. Li Baochen's alliance with Tian Chengsi, who controlled Weibo Circuit (魏博, headquartered in modern
Handan,
Hebei), would be severely tested in 775, as Tian, despite the alliance, looked down at his allies and had seized most of Xue Song's Zhaoyi Circuit (昭義, headquartered in modern
Anyang,
Henan) after Xue's death in 773 rather than allowing Xue's family to retain the territory. In or shortly before 775, there was an incident where Li Baozheng and Tian's son Tian Wei () were playing
polo at Weibo, when an accidental collision between Li Baozheng's and Tian Wei's horses killed Tian Wei. Tian Chengsi, in anger, imprisoned Li Baozheng and sent a messenger to Li Baochen in protest. Li Baochen, wanting to be conciliatory, sent a cane back with Tian's messenger and allowed Tian to discipline Li Baozheng — but Tian, in anger over his son's death, caned Li Baozheng to death, causing Li Baochen to break off the alliance with Tian. He and Li Zhengji, who also felt slighted by Tian, submitted petitions to the imperial government asking to attack Tian, and Emperor Daizong agreed, launching troops from a number of circuits loyal to the imperial government, in addition to Li Baochen's and Li Zhengji's forces, to attack Tian. Li Baochen,
Zhu Tao (whose brother
Zhu Ci had killed Zhu Xicai in 772, submitted Lulong to Tang imperial authority, and went to Chang'an to serve as
chancellor, leaving Zhu Tao in command of Lulong), and Xue Jianxun () the military governor of Taiyuan Circuit attacked Tian from the north, while Li Zhengji and
Li Zhongchen the military governor of Huaixi Circuit (淮西, headquartered in modern
Zhumadian,
Henan) attacked Tian from the south. Initially, these joint forces were successful in their attacks against Tian, seizing Ci Prefecture (磁州, in modern Handan) from Tian, but Tian was subsequently able to persuade Li Zhengji to break off his attack, substantially weakening the joint forces. Meanwhile, Li Baochen was offended when an imperial
eunuch, Ma Chengqian (), who had visited Li Baochen's army, was so dissatisfied with Li Baochen's gift to him that he threw it on the ground, and Tian was also able to use hoaxes to persuade Li Baochen that if he joined forces with Tian to attack Lulong, he would be successful. Li Baochen thus turned against Zhu Tao, launching a surprise attack on him, but was unable to kill Zhu Tao, effectively ending any hopes of the campaign against Tian and subsequently creating an enmity between the Chengde and Lulong Circuits. Tian subsequent ceded Cang Prefecture (滄州, in modern
Cangzhou,
Hebei) to LI Baochen, cementing the reformed alliance and increasing Li Baochen's holdings to seven prefectures. By 777, Li Baochen had an army that was 50,000-men strong, and Emperor Daizong created him the Prince of Longxi. In 778, for reasons unclear in history, Li Baochen briefly assumed his old surname of Zhang. However, in 779, he became apprehensive about having done so, and, with Emperor Daizong's permission, reassumed the imperial surname of Li. Also in 779, when Tian Chengsi died, it was at the urging of Li Baochen that Emperor Daizong officially approved Tian Chengsi's selected successor, his nephew
Tian Yue, as Tian Chengsi's successor. As Li Baochen grew older, he was planning to pass his territory to his son
Li Weiyue, but as Li Weiyue was described to be weak in personality, he feared that Li Weiyue would not be able to control the army. Therefore, he began to systematically kill the stronger military officers in his army to eliminate potential challengers to Li Weiyue. The only officers to escape this fate were
Zhang Xiaozhong the prefect of Yi Prefecture (易州, in modern
Baoding,
Hebei) — who resisted repeated summons by Li Baochen and stayed at Yi Prefecture, although not turning against Li Baochen while Li Baochen was alive — and Wang Wujun, who was close to Li Baochen and whose son
Wang Shizhen had married Li Baochen's daughter. It was also said that in his old age, he became particularly superstitious and trusted sorcerers who predicted that he would have long life and supreme power (i.e., become emperor). In 781, the sorcerers made him a potion that was supposed to yield long life, but instead was poisonous, and he died within three days of drinking it. Li Weiyue would succeed him without Tang imperial approval, and by 782 was killed by Wang, ending the Li family's hold on Chengde. == Family ==