Emperor Daizong of Tang (11 November 726 – 10 June 779), personal name Li Yu (name changed in 758 after being created crown prince), né Li Chu (Chinese: 李俶), was an emperor of the Chinese Tang dynasty.
Emperor Daizong was the eldest son of Emperor Suzong – the first emperor of the Tang dynasty to succeed as the eldest child. During the Anshi Rebellion (which Emperor Suzong's entire reign was dedicated to fighting), he served as a general of Tang and Huige joint operations that recaptured the capital Chang'an and the eastern capital Luoyang from the rebel state of Yan, and the Anshi Rebellion was finally put down early in his own reign, in 763. However, thereafter, the Tang state was plagued by warlords such as Tian Chengsi, Li Baochen, and Liang Chongyi who essentially governed their realms as independent states while only pledging nominal loyalty to the emperor. This would prove disastrous for future generations as subsequent Tang emperors were unable to remove or control these warlords and the central government's power was thus slowly eroded and diminished. The power of the warlords would not prevent the Tang western territories from being overrun by Tibetan invasions and eventually lost to the Tibetan Empire, which even managed to capture Chang'an in 763 for a short period before being expelled.
Emperor Daizong was credited for removing the corrupt eunuch Li Fuguo, who had placed him on the throne using their own power and political influence, later the rest of Emperor Daizong's reign would also see dominance by such individuals as the eunuchs Cheng Yuanzhen and Yu Chao'en, as well as the chancellor Yuan Zai. It is also worth noting that Emperor Daizong became the first Tang emperor to succeed to the throne as a result of maneuvers by eunuchs. Emperor Daizong was himself also said to be overly devout in Buddhism.
Daizong's father, Li Jun, was the Prince of Zhong under his father Emperor Xuanzong when Daizong was born. His mother was Li Jun's concubine Consort Wu. He was the oldest of Emperor Xuanzong's over 100 grandsons. In 740, by which time Li Jun (whose name had been changed to Li Heng by that point) was crown prince, Li Chu was created the Prince of Guangping. That year, his mother Consort Wu died. In his youth, he was said to be kind, meek, and filially pious, and was studious, particularly in the Classic of Rites and the I Ching. He was much favored by his grandfather. Emperor Xuanzong chose for him, as his wife and princess, Lady Cui the daughter of the Lady of Han, a sister of Emperor Xuanzong's favorite concubine Consort Yang Yuhuan; however, his oldest son Li Kuo was born of a concubine, Consort Shen.
In 755, the general An Lushan rebelled at Fanyang (范陽, in modern Beijing), and by summer 756, the forces of his new state of Yan were approaching the Tang capital Chang'an, forcing Emperor Xuanzong to flee to Chengdu. When Emperor Xuanzong's train reached Mawei Station (馬嵬驛, in modern Baoji, Shaanxi), angry soldiers, blaming the rebellion on the chancellor Yang Guozhong (Consort Yang's cousin), killed Yang Guozhong and his family members and forced Emperor Xuanzong to kill Consort Yang. Subsequently, the people in the Mawei region tried to persuade Emperor Xuanzong not to continue on to Chengdu—believing that Chang'an could be recaptured. Emperor Xuanzong asked Li Heng to try to comfort the people. Once Li Heng left Emperor Xuanzong's presence, however, Li Heng's trusted eunuch Li Fuguo, Li Chu's brother Li Tan the Prince of Jianning, and Li Chu, persuaded Li Heng not to follow Emperor Xuanzong to Chengdu—arguing that with the physical barriers between Chang'an and Jiannan Circuit (劍南, headquartered in modern Chengdu), that once they had left the region, Chang'an could no longer be captured. Li Heng agreed and had Li Chu report this to Emperor Xuanzong. Emperor Xuanzong agreed with Li Heng's decision, but he himself continued on to Jiannan. Li Heng, escorted by a small number of guard soldiers commanded by Li Tan, then headed to the border city of Lingwu. With the army at Lingwu pressuring him to take imperial title, Li Heng declared himself emperor (as Emperor Suzong).
After Emperor Suzong assumed imperial title, he considered making Li Tan the supreme commander of the armed forces, but his advisor Li Mi pointed out that Li Chu was older and that naming Li Tan the supreme commander would cause confusion as to who would be his heir. Emperor Suzong agreed and made Li Chu the supreme commander instead. Subsequently, Li Chu and Li Mi were entrusted with the keys of the makeshift palace, and one would always be on duty to be ready to receive important military reports. In 757, Emperor Suzong considered creating Li Chu crown prince, but Li Mi and Li Chu, pointing out that it would be inappropriate to do so before Chang'an were recaptured, advised him otherwise. Subsequently, Emperor Suzong's court was also itself filled with internal struggles, with Li Fuguo aligned with Emperor Suzong's favorite concubine Consort Zhang, in opposition to Li Chu, Li Tan, and Li Mi. In early 757, after Li Tan repeatedly accused Li Fuguo and Consort Zhang of corruption, Li Fuguo and Empress Zhang in turn falsely accused him of trying to assassinate Li Chu in order to become the heir. Emperor Suzong, in anger, ordered Li Tan to commit suicide, which drew fear from Li Chu and Li Mi. Li Chu considered assassinating Li Fuguo and Consort Zhang, but at Li Mi's urging, stopped his plans to do so.
In fall 757, troops from Huige, whose Bayanchur Khan Yaoluoge Moyanchuo had answered Emperor Suzong's request for help, arrived under the command of Yaoluoge Moyanchuo's son. When Li Chu met the Huige prince, he offered for them to be sworn brothers. The prince was very pleased and honored Li Chu as an older brother. Thereafter, the joint Tang and Huige troops proceeded toward Chang'an and, after defeating Yan forces at Xiangji Temple (香積寺), near Chang'an, recaptured Chang'an. Emperor Suzong had promised that Huige forces would be allowed to pillage Chang'an, but at the earnest pleas of Li Chu, the Huige prince agreed to wait until capturing Luoyang, which had become the Yan capital, to carry out the pillage. The people of Chang'an, believing that Li Chu had saved them from a deadly Huige rampage, welcomed him in a grand procession and proclaimed, "The Prince of Guangping is truly a leader to be loved by both the Han and the barbarians." Meanwhile, when Pugu Huai'en advocated quick advances to try to capture the Yan generals An Shouzhong (安守忠) and Li Guiren (李歸仁), Li Chu, pointing out that his own troops were tired, stopped him. (Upon the recapturing of Chang'an, Li Mi resigned and became a hermit, depriving Li Chu of an ally.)
Subsequently, Li Chu, Guo Ziyi, and Pugu, along with Huige forces, continued to proceed toward Luoyang. They first attacked Shancheng (陝城, in modern Sanmenxia, Henan) and initially could not succeed, but when Huige forces engaged, Yan forces were thrown into a panic and fled. Hearing the news, An Lushan's son and successor An Qingxu, who had become the emperor of Yan, abandoned Luoyang and fled. Once Huige forces entered Luoyang, they went on a rampage. Li Chu had the people gather up a large cache of silk to bribe the Huige prince, and only thereafter did the rampage end.
Upon Li Chu's entry into Luoyang, he initially announced that the Tang officials who had surrendered to Yan would be forgiven. However, soon they were rearrested and delivered to Chang'an. Several were executed, while many others were punished by demotion or exile. In winter 757, Li Chu returned to Chang'an with Guo, and was subsequently created the greater title of Prince of Chu. In spring 758, his title was changed to Prince of Cheng. Emperor Suzong wanted to further create him crown prince, but hesitated because Consort Zhang, who had since been created empress, had a son named Li Shao (李佋), carrying the title of Prince of Zhao, whom she wanted to be crown prince. When he consulted the chancellor Li Kui, Li Kui advocated for Li Chu, and Emperor Suzong agreed, creating Li Chu crown prince on June 29, 758. He also changed Li Chu's name to Li Yu. However, it was said that Empress Zhang did not give up the idea of having Li Shao become crown prince and was looking for ways to undermine Li Yu. Li Yu tried to react with meekness and humility. After Li Shao died in 759, because Empress Zhang's other son, Li Tong (李侗) the Prince of Ding was still young, Li Yu's position was no longer threatened.