Biography
Family Background and Early Life
Yang You was born into the Sui imperial family. The source states that his grandfather was Emperor Wen of Sui, Yang Jian, and that his father Yang Zhao was the eldest son of Emperor Yang of Sui, Yang Guang. Yang Zhao was made Crown Prince in 605, the first year of Daye, but died the following year, in 606, at the age of twenty-three. After Yang Zhao’s death, his sons Yang You, Yang Tong, and others were raised by their grandfather Emperor Yang of Sui. In 607, the third year of Daye, the two-year-old Yang You was enfeoffed as Prince of Chen and soon afterward changed to Prince of Dai. His elder brother Yang Tong was later enfeoffed as Prince of Yue and became known as the Huangtai ruler.
Guarding Chang'an and Passive Accession
In 616, the twelfth year of Daye, Emperor Yang made his third journey to Jiangdu, modern Yangzhou in Jiangsu. Before leaving, he ordered Yang You to remain in the western capital Chang'an, while Prince of Yue Yang Tong stayed in the eastern capital Luoyang. By then the Sui Dynasty was rapidly disintegrating amid widespread rebellions. Li Yuan, garrison commander of Taiyuan, raised troops at Jinyang in 617 and marched west. In the eleventh month he entered Chang'an. Li Yuan initially acted under the slogan of preserving the Sui rather than immediately proclaiming himself emperor. He therefore installed Prince of Dai Yang You as emperor, changed the era name to Yining, and honored Emperor Yang, who remained at Jiangdu, as Retired Emperor. Yang You was twelve and entirely under Li Yuan’s control, becoming a puppet ruler.
Abdication and Death
In the third month of 618, the second year of Yining, Emperor Yang was killed by Yuwen Huaji in the palace at Jiangdu. After the news reached Chang'an, Li Yuan regarded Yang You’s political usefulness as exhausted. In the fifth month he forced Yang You to abdicate, proclaimed himself emperor, founded the Tang Dynasty, and became Emperor Gaozu of Tang. Yang You was reduced to Duke of Xi and lived in retirement in Chang'an. On September 14, 619, corresponding to the dingyou day of the eighth lunar month in the second year of Wude, Yang You died at the nominal age of fifteen. He received the posthumous title Emperor Gong and was buried at Zhuangling. The historical record states only that he “died” and does not explicitly say that he was poisoned, although later writers often believed that his death was unnatural.
Major Activities
Puppet Emperor
Yang You reigned for only about half a year, from the eleventh month of 617 to the fifth month of 618. All major political affairs were controlled by Li Yuan and his supporters. Li Yuan issued commands in Yang You’s name as part of the political process leading to his own accession. Yang You was too young to affect events and served only as the nominal head of state.
Abdication and Deposition
In the fifth month of 618, Yang You was forced to abdicate in favor of Li Yuan, marking the establishment of the Tang Dynasty. After abdication he was enfeoffed as Duke of Xi and retained certain formal privileges but no real power. His abdication marked the formal end of the Sui Dynasty.
Posthumous Succession
Yang You had no son. According to the *Institutional History of Tang* and other sources, the Sui imperial clansman Yang Xingji was adopted as his heir and inherited the title Duke of Xi.
The stages of his short life can be set out by year: born in 606 (second year of Daye), his father Yang Zhao, the Yuande crown prince, dying when he was one; enfeoffed as Prince of Chen in 607 (third year of Daye) and later transferred to Prince of Dai; in 616 (twelfth year of Daye), at eleven, left in charge of Chang'an while Emperor Yang toured Jiangdu; in 617 (first year of Yining), at twelve, made emperor by Li Yuan after his entry into Chang'an, with the era name Yining and Emperor Yang honoured at a distance as retired emperor; in 618 (second year of Yining), with Emperor Yang killed at Jiangdu, forced by Li Yuan to abdicate and reduced to Duke of Xiguo; and in 619 (second year of Wude), at fifteen, he died with the posthumous title Emperor Gong and was buried at the Zhuang Mausoleum. His passage from a prince left in charge to a ruler installed by Li Yuan and then to abdication shows that politics at Chang'an in the last years of the Sui lay wholly with Li Yuan, while his posthumous title and burial place are also recorded in Tang historical sources.
As to the politics of the end of the Sui and the beginning of the Tang, the installation and abdication of Yang You form one link in Li Yuan's course from his rising at Taiyuan to the founding of the Tang: in 617, on entering Chang'an, Li Yuan did not at once take the imperial title but installed Yang You as emperor and honoured Emperor Yang at a distance as retired emperor, holding power in the name of reverence for the Sui; in 618, after Emperor Yang was killed at Jiangdu, Li Yuan forced Yang You to abdicate and founded the Tang. Yang You was throughout a clansman installed by others, no independent decision being recorded in his career from accession at twelve to death at fifteen; his reduction to Duke of Xiguo, his posthumous title Emperor Gong and his burial at the Zhuang Mausoleum are recorded in the two Books of Tang and in the relevant parts of the *Book of Sui*.
He reigned less than a year, the era name Yining being used until his abdication.
As to the passage from Sui to Tang, Yang You's part was to provide the name of reverence for the Sui: Li Yuan had risen under the banner of honouring the Sui, and in entering Chang'an he installed Yang You rather than taking the throne himself, which both calmed the old officials of the Sui and the gentry of Guanzhong and gave him the advantage of legitimacy in competition with the other contenders; once Emperor Yang was killed at Jiangdu and no Sui sovereign remained to rely on, Li Yuan accepted the abdication and founded the Tang. Yang You was from the first a nominal ruler in this process, his accession, change of era name and abdication all arranged by Li Yuan's side; the two Books of Tang and the *Book of Sui* record him briefly, preserving chiefly his title, accession, reduction in rank and death.
His era name Yining, his posthumous title Emperor Gong and his burial at the Zhuang Mausoleum are the chief designations his short life left behind.
He never took personal rule, government being conducted by Li Yuan as grand chancellor.
The two years between his reduction in rank and his death fell in the period when the new Tang was consolidating against the regional contenders.
His titles continued in use in official documents at the transition from Sui to Tang.
The location of his Zhuang Mausoleum is also recorded in later histories.
His posthumous name Gong corresponds to the sequence of titles of the Sui sovereigns.
The era name Yining of his reign was used until his abdication; the two Books of Tang say only briefly that after his reduction to Duke of Xiguo he died in the second year of Wude.