Emperor Shunzong of Tang - As Crown Prince

As Crown Prince

Li Song was described to be kind and lenient. He favored the study of arts, and was particularly good at calligraphy. He was also respectful to his teachers and often bowed to them despite his crown prince status. In 781, he married Lady Xiao, the daughter of his grandaunt Princess Gao and her husband Xiao Sheng (蕭升), as his wife and crown princess.

In 783, when a mutiny by soldiers from Jingyuan Circuit (涇原, headquartered in Pingliang, Gansu) forced Emperor Dezong to abandon Chang'an and flee to Fengtian (奉天, in modern Xianyang, Shaanxi), Li Song accompanied Emperor Dezong to Fengtian, and was said to have personally protected Emperor Dezong during the journey to Fengtian, along with his younger brother Li Yi (李誼) the Prince of Pu. After the Jingyuan soldiers supported the general Zhu Ci as their emperor (of a new state of Qin), Zhu put Fengtian under siege, and Li Song was said to have personally participated in the defense of Fengtian, including personally encouraging soldiers and attending to the wounded.

After the rebellion was put down and Emperor Dezong and his family returned to Chang'an, Li Song's position was endangered over an incident involving his grandaunt/mother-in-law Princess Gao. As of 787, the chancellor Zhang Yanshang had discovered that the imperial guard officer Li Sheng (李昇) was secretly visiting Princess Gao, and he came to suspect that Li Sheng, whose father Li Shuming (李叔明) was a political enemy of Zhang's, was having an affair with Princess Gao. Initially, at the advice of another chancellor, Li Mi — who feared that an investigation would taint Li Song — Emperor Dezong took no actions against anyone other than to transfer Li Sheng out of the imperial guards to avoid contact with Princess Gao. However, by fall 787, the incident had flared up in public, as accusations were made that Princess Gao, who often visited Li Song's palace, was having affairs not only with Li Sheng, but also with other officials Xiao Ding (蕭鼎), Li Wan (李萬), and Wei Ke (韋恪); worse, she was also accused of secretly using witchcraft to curse Emperor Dezong. Emperor Dezong, in anger, imprisoned Princess Gao and became angry at Li Song. Li Song, fearing the taint, divorced Crown Princess Xiao, but Emperor Dezong's anger did not recede, and he considered replacing Li Song as crown prince with Li Yi. At Li Mi's earnest opposition, Emperor Dezong ultimately decided not to do so. The former crown princess was later killed on Emperor Dezong's orders, during a time when Li Song was ill.

In 795, after the former chancellor Lu Zhi and several of his associates was exiled due to false accusations by Emperor Dezong's favorite Pei Yanling, the imperial scholar Yang Cheng (陽城) led a group of junior officials in petitioning Emperor Dezong in protesting Lu's innocence, drawing Emperor Dezong's anger toward them. Emperor Dezong were initially set to punish Yang and the other junior officials, but after Li Song spoke on their behalf, Emperor Dezong did not do so. It was also said that it was Li Song's urging that Pei and another favorite of Emperor Dezong's, Wei Qumou (韋渠牟), who were poorly regarded by the people, were not made chancellors.

By 803, Li Song had become close to two of his staff members — Wang Pi, who was also a talented calligrapher, and Wang Shuwen, who was good at playing Go. It was said at that Wang Shuwen's suggestion, Li Song avoided drawing further suspicion from Emperor Dezong. (Li Song was set to speak to Emperor Dezong against Emperor Dezong's unpopular Palace Market (宮市) — where palace eunuchs were effectively requisitioning supplies from merchants while paying no or very little compensation, and Wang Shuwen pointed out that this would cause Emperor Dezong to suspect Li Song of trying to be popular at his expense.) At Wang Shuwen's suggestion, Li Song also began to gather a group of junior officials that Wang Shuwen had befriended and considered capable of being important officials and generals in the future, including Wei Zhiyi, Lu Chun (陸淳), Lü Wen (呂溫), Li Jingjian (李景儉), Han Ye (韓曄), Han Tai (韓泰), Chen Jian (陳諫), Liu Zongyuan, Liu Yuxi, Ling Zhun (凌準), and Cheng Yi, in anticipation of his future reign.

In winter 804, Li Song suffered a stroke that left him partially paralyzed and unable to speak. When subsequently, Emperor Dezong became ill as well, members of the imperial family attended to him, but Li Song was unable to do so. This saddened Emperor Dezong greatly and caused his own conditions to grow worse, and he died on February 25, 805. Initially, the palace eunuchs expressed the opinion that perhaps Li Song should not succeed to the throne, but after the imperial scholar Wei Cigong (衛次公) spoke firmly in Li Song's favor, and Li Song, despite his illness, appeared to show that he was not completely incapacitated, he was able to succeed to the throne (as Emperor Shunzong).