The Niu–Li factional strife (Chinese: 牛李黨爭; pinyin: Níu Lǐ dǎngzhēng) was an ongoing contention at the court of the mid-to late Tang dynasty.
Traditionally, the seeds of the Niu–Li factional strife were seen to have been sown in 808, when Emperor Xianzong held a special imperial examination for the examinees to give honest criticism of government.
The officials in charge of the examination, Wei Guanzhi and Yang Yuling (楊於陵), selected three examinees who gave blunt criticism—Niu Sengru, Huangfu Shi (皇甫湜), and Li Zongmin—for top marks.
Niu, Huangfu, and Li Zongmin were not exiled, but were said in the Zizhi Tongjian to be effectively stalled in their careers, forcing them to find governmental positions themselves under regional governors.
Meanwhile, Li Zongmin's junior colleague at the legislative bureau, Yang Rushi (楊汝士), and the deputy minister of rites (禮部侍郎, Libu Shilang) Qian Hui (錢徽), were in charge of overseeing the imperial examinations.
The military governor (Jiedushi) Duan Wenchang (a former chancellor) and the imperial scholar Li Shen both made secret pleas to Qian for certain examinees.
However, when the results were announced, the examinees that Duan and Li Shen recommended were not given passing results, while among those passing the examinations were Zheng Lang, the brother of the examination bureau (門下省, Menxia Sheng) official Zheng Tan; Pei Zhuan (裴譔) the son of the military governor Pei Du (also a former chancellor); Li Zongmin's son-in-law Su Chao (蘇巢); and Yang Rushi's brother Yang Yinshi (楊殷士).
At that time, Li Deyu, who had become the governor (觀察使, Guanchashi) of Zhexi Circuit (浙西, headquartered in modern Zhenjiang, Jiangsu), was considered a potential chancellor candidate as well, and as he was passed over in this selection and would eventually not be promoted for a stretch of eight years.
Believing Wang's assertions, Emperor Jingzong exiled Li Shen to be the military advisor to the prefect of Chao Prefecture (潮州, in modern Chaozhou, Guangdong), and demoted two imperial scholars that Li Shen had recommended, Pang Yan (龐嚴) and Jiang Fang (蔣防), to be prefects of two other distant prefectures.
Also, that year after Emperor Jingzong declared a general pardon, Li Fengji submitted a proposed edict announcing the general pardon that would permit those exiled officials who had previously received a movement toward Chang'an be given another one, but not stating anything with regard to those exiled officials who had never received a previous movement toward Chang'an.
At Wei's suggestion, the edict was revised, allowing Li Shen to be moved to Jiang Prefecture (江州, in modern Jiujiang, Jiangxi) to serve as its secretary general.
[4] In 826, Emperor Jingzong summoned Pei (viewed by some later historians as a Li Party leader)[5] back to the capital and made him chancellor again.
[6] Li Deyu himself was sent to Xichuan Circuit (西川, headquartered in modern Chengdu, Sichuan), which had recently been devastated by a Nanzhao incursion, as its military governor.
Emperor Wenzong accepted his argument and ordered that Li Deyu return Wei Prefecture, as well as Xidamou and his soldiers, to Tufan.
The massacre brought much popular sentiment against Niu, and was commonly viewed at the time to be the result of the conflict between Niu/Li Zongmin and Li Deyu.
Around the new year 833, Emperor Wenzong made Niu the military governor of Huainan Circuit (淮南, headquartered in modern Yangzhou, Jiangsu).
Soon thereafter, Li Zongmin himself was sent out to Shannan West Circuit (山南西道, headquartered in modern Hanzhong, Shaanxi), to serve as its military governor.
[6] Subsequently, at Zheng Zhu's recommendation, Li Zhongyan, a former official who had been exiled due to crimes, also became a close associate of the emperor.
Lu Sui spoke in defense of Li Deyu, and he was relieved of his duties and exiled to Yuan Prefecture (袁州, in modern Yichun, Jiangxi) to serve as its secretary general.
Lu himself suffered the consequences of being sent out to Zhenhai to serve as its military governor and, contrary to the regular official movements at the time, he was not allowed to meet with Emperor Wenzong before his departure.
This caused much panic in the public, and Zheng, who had long disliked Yang Yuqing, accused his family members of spreading the rumors.
Emperor Wenzong exiled Li Zongmin to serve as the prefect of Ming Prefecture (明州, in modern Ningbo, Zhejiang).
To this end, in winter 835, Zheng was made the military governor of Fengxiang Circuit (鳳翔, headquartered in modern Baoji, Shaanxi) with the intent that he get his soldiers ready for such an event.
[10] In the aftermaths of the Ganlu Incident, Li Shi and Zheng Tan were made chancellors, and while most of the power remained in the leading eunuchs' hands, it was said because of a severely worded petition filed by the military governor Liu Congjian objecting to the deaths of Wang Ya and Jia, the powerful eunuchs began to show some restraint, allowing Emperor Wenzong and the chancellors to have some ability to govern.
Meanwhile, Li Zongmin was moved closer to the capital, to be the military advisor to the prefect of Heng Prefecture (modern Hengyang in Hunan).
Li Shi, in the aftermath, became apprehensive and offered to resign, and he was sent to Jingnan Circuit (荊南, headquartered in modern Jingzhou, Hubei) to serve as its military governor.
[14] Emperor Wuzong rewarded Li Deyu with great honors in light of the victory over Liu Zhen, including the title of the Duke of Zhao.
However, at the same time, Li Deyu was drawing resentment over his domination of the court scene—and was particularly despised in his having Emperor Wuzong issue a posthumous edict condemning the relatives of Wang Yai, Jia Su, and Li Xun, who had fled to Zhaoyi and been protected by Liu Congjian but whom Guo slaughtered after killing Liu Zhen.
Emperor Xuānzong also made Li Deyu the defender of Luoyang and removed the honorary chancellor title that he continued to carry as the military governor of Jingnan from him, further showing disapproval.
Emperor Xuānzong also demoted other officials who were considered complicit or negligent in Wu Xiang's death, and posthumously stripped Li Shen's offices.