After succeeding to the throne, Muzong spent his time feasting and heavily drinking, thereby neglecting his duties as emperor.

His mother Princess Guo, however, despite her having been Li Chun's wife, was not created empress, but only an imperial consort, albeit with the high rank of Guifei (貴妃).

Emperor Xianzong removed Wei from his post as attendant, and soon sent him out of the capital Chang'an to serve as the prefect of Qian Prefecture (虔州, in modern Ganzhou, Jiangxi).

Tutu, however, did not relent in his hopes to have Li Yun made crown prince, even by 820, when Emperor Xianzong had become seriously ill. Li Heng, worried about what would happen next, requested advice from his uncle (Consort Guo's brother) Guo Zhao (郭釗), who advised him to simply serve his father with filial piety and not worry about the rest.

Wang Chengyuan pretended to accept their support, but declared his loyalty to the imperial government and secretly petitioned Emperor Muzong to replace him.

Emperor Muzong reacted by, against the advice of the general Yang Yuanqing (楊元卿),[14] moving Tian Hongzheng the military governor of Weibo—whose submission to the imperial government in 812 had been a crucial step in the Yuanhe Restoration[8] and who had been a major participant in the subsequent campaigns against Chengde and Pinglu[8][10][11]—to Chengde, Wang Chengyuan to Yicheng Circuit (義成, headquartered in modern Anyang, Henan), Liu Wu from Yicheng to Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), Li Su from Wuning Circuit (武寧, headquartered in modern Xuzhou, Jiangsu) to Weibo, and made Tian Hongzheng's son Tian Bu the military governor of Heyang Circuit (河陽, headquartered in modern Jiaozuo, Henan).

When he requested that the imperial government supply the salaries of these Weibo soldiers, however, the acting director of finances, Cui Ling (崔倰), a relative of the chancellor Cui Zhi, not understanding the seriousness of the situation, believed that it was the Chengde soldiers' responsibility to protect their military governor, refused.

He also requested an award to the soldiers, while ordering a number of officers that he felt were difficult to control, including Zhu Kerong (the grandson of a former military governor, Zhu Tao) to report to Chang'an, hoping that the imperial government would give them proper discipline and rewards such that they would become faithful to the imperial government.

Meanwhile, Li Su planned a campaign against Wang and Zhu, but fell ill, and was replaced by Tian Bu as the military governor of Weibo.

Emperor Muzong commissioned Pei Du, a key chancellor during Emperor Xianzong's reign, to oversee the entire operation against Lulong and Chengde, which also included such renowned imperial generals as Wu Chongyin and Li Guangyan and had some 150,000 soldiers in total, against the less than 10,000 soldiers that the rebels had.

The imperial government was forced to capitulate, and soon also named Zhu and Wang military governors of their circuits as well, ending the campaign against them.

From this point on, until the eventual fall of the Tang dynasty altogether in 907, the imperial government was never again able to assert direct control over Chengde, Lulong, or Weibo.

Investigations did not yield positive evidence for the allegations, but as a result, both Pei and Yuan were removed from the chancellor posts.

The chancellor Du Yuanying and the official Zhang Pingshu (張平叔) advocated placating the mutineers' leader Li Jie (李㝏) by making him military governor, but the chancellor Li Fengji opposed, arguing that effectively abandoning control over Xuanwu would lead to the eventual loss of the Yangtze River-Huai River region.

With the prefects of the three Xuanwu prefectures other than the capital prefecture Bian Prefecture (汴州) all petitioning for a new military governor rather than Li Jie, however, Emperor Muzong decided to act against Li Jie by making Han Chong (韓充), the brother of former long-time Xuanwu military governor Han Hong, military governor, and have him head toward Xuanwu, while commissioning Li Jie as a general of the imperial guards.

[14] In 823, impressed with the official Niu Sengru for having refused gifts from the now-deceased Han Hong while virtually the rest of the entire imperial administration had received Han's gifts, Emperor Muzong made Niu chancellor, disappointing that similarly highly regarded governor of Zhexi Circuit (浙西, headquartered in modern Zhenjiang, Jiangsu), Li Deyu.

[16] Played by Eric Li, a fictionalized version of Muzong was portrayed in 2009 Hong Kong's TVB television series, Beyond the Realm of Conscience.