Empress Zhangsun in the context of "Tuoba"

Emperor Gaozong of Tang (21 July 628 – 27 December 683), personal name Li Zhi, was the third emperor of the Chinese Tang dynasty, ruling from 649 to 683; after January 665, he handed power over the empire to his second wife Empress Wu (the future Wu Zetian), and her decrees were carried out with greater force than the decrees of Emperor Gaozong's. Emperor Gaozong was the youngest son of Emperor Taizong and Empress Zhangsun; his elder brothers were Li Chengqian and Li Tai.

Emperor Gaozong's reign saw the primacy of Empress Wu, who became the effective power behind the Tang rule. Empress Wu aided Emperor Gaozong in his rule during the later years of his reign after a series of strokes left him incapacitated. Emperor Gaozong effectively after January 665 delegated all matters of state to Empress Wu; after that the empress acted as the power behind the emperor, "hanging the curtain and listening to politics" (垂簾聼政; Chuílián tīngzhèng). Gaozong's personal illness, affection and trust of Wu led to her wielding a great deal of power in affairs of state until the end of his reign. From official histories from the later Tang Dynasty to contemporary historians, there exists a lively debate about whether Wu exerted undue influence on Gaozong, or whether they were equal partners in the government. Empress Wu was partially in control of power from November 660 and then totally from January 665 to December 683; there was an equality of power between Gaozong and Wu, which caused them to be called "two saints" (二聖; Er Sheng, literally two emperors) both inside and outside. After Emperor Gaozong died in December 683, power fell completely and solely into the hands of Empress Wu, acting as Empress Dowager-regent, "presiding over court and issuing edicts" (臨朝稱制; lin chao chengzhi); she subsequently became the only empress regnant in Chinese history. After his death, he was interred at the Qian Mausoleum along with Wu Zetian.

Li Chéngqián (李承乾) (619 – 5 January 645), courtesy name Gaoming (高明), formally Prince Min of Hengshan (恆山愍王), was a crown prince of the Chinese Tang dynasty. He was Emperor Taizong's oldest son and first crown prince, but was replaced later by his younger brother Li Zhi (the eventual Emperor Gaozong).

Li Chengqian was created crown prince in 626 at the age of eight (by East Asian reckoning), after his father became emperor on 4 September. In his youth, he had a reputation for good judgment, but was also said to be suffering from a foot illness. Later on, he was said to be frivolous, favoring Tujue customs instead of studying about ways to rule an empire. He lost favor in Emperor Taizong's eyes to a younger brother, Li Tai the Prince of Wei. (Both had the same mother, Emperor Taizong's wife Empress Zhangsun.) In 643, in fear that Emperor Taizong was about to depose him in favor of Li Tai, he plotted with the general Hou Junji to overthrow Emperor Taizong. The plot was discovered, and he was deposed and reduced to commoner rank, but Emperor Taizong, believing that Li Tai to be responsible for Li Chengqian's downfall, appointed yet another son, Li Zhi (also by Empress Zhangsun), crown prince instead. Li Chengqian was exiled, and died in exile in January 645, as a commoner under house arrest. He was posthumously granted an imperial prince title during the reign of his grandnephew, Emperor Xuanzong after his grandson Li Shizhi became chancellor.