Xiao Yu - During Emperor Gaozu's Reign

During Emperor Gaozu's Reign

Also in spring 618, Emperor Yang was killed at Jiangdu (江都, in modern Yangzhou, Jiangsu) in a coup led by the general Yuwen Huaji. When the news reached Chang'an, Li Yuan had Emperor Gong yield the throne to him, establishing Tang Dynasty as its Emperor Gaozu. He made Xiao Yu Neishi Ling (內史令), the head of the legislative bureau of the government (內史省, Neishi Sheng) and a post considered one for a chancellor, and he entrusted Xiao with some of the most important matters of state. Whenever Emperor Gaozu held imperial gatherings, he would allow Xiao to sit next to him, and particularly, because Xiao had married a member of the Dugu clan, from which Emperor Gaozu's mother Lady Dugu also came, Emperor Gaozu referred to him endearingly as "Master Xiao." Xiao took the matters of state seriously and was not afraid of offending others in offering suggestions, and people feared him. When Li Shimin was made the governor of the capital prefecture Yong Prefecture (雍州, i.e., Chang'an and its surrounding counties), Xiao was given the additional title of commandant of Yong Prefecture. In 619, he and Pei Ji were in charge of interrogating one of the major initial contributors to Emperor Gaozu, Liu Wenjing, who had been arrested on suspicion of treason. Both he and Li Gang (李綱), as well as Li Shimin, tried to intercede on Liu's behalf, but Emperor Gaozu nevertheless executed Liu on Pei's recommendations. Later, after the legislative bureau was renamed Zhongshu Sheng (中書省) in 620, Xiao Yu remained its head with the new title of Zhongshu Ling (中書令). Per Xiao's recommendations, Emperor Gaozu made Feng Deyi Zhongshu Ling as well, sharing the position with Xiao. In 621, he was similarly put in charge, along with Pei and Chen Shuda, of interrogating Li Zhognwen (李仲文) the Duke of Zhenxiang, who was also charged with treason, and while Xiao's recommendations were unclear, Li Zhongwen was also executed.

At times, when Emperor Gaozu issued edicts, he wanted the legislative bureau to promulgate them quickly, but Xiao did not do so. When Emperor Gaozu rebuked him, Xiao pointed out that during Emperor Yang's reign, the edicts were issued quickly, and while officials had valid reservations, they did not dare to speak against it. He wanted the edicts to be issued only after greater examination, and so was not issuing them as quickly. Emperor Gaozu agreed. Meanwhile, as Xiao's property was initially seized by Emperor Gaozu when he first entered Chang'an to be awarded to the military officers with accomplishments, Emperor Gaozu returned the property to Xiao. Xiao divided the property and distributed it to his clan members, only keeping the family shrine so thathe could sacrifice to the ancestors. After Li Shimin destroyed a major rival, Wang Shichong the Emperor of Zheng, in 621, Xiao, who served under Li Shimin during the campaign and was credited with some of the strategies (as well as charged with collecting the Sui imperial treasury stores at the Zheng capital Luoyang), was given 2,000 additional households as part of his fief and made one of the deputy heads of the important executive bureau of government (尚書省, Shangshu Sheng), Shangshu Pushe, still considered a chancellor position. As Shangshu Pushe, Xiao was considered diligent but biased, as well as harsh, and he did not have as good of a reputation.

In 626, when Fu Yi (傅奕) the director of the imperial astronomical observatory, a Confucian, submitted a proposal to ban Buddhism on the grounds that Buddhism was leading to corruption and abuses within the government, Xiao, as a devout Buddhist, debated with Fu earnestly before Emperor Gaozu. He was unable to prevail over Fu in the debate, and Emperor Gaozu issued an edict severely limiting the number of Buddhist temples, although the edict did not appear to be seriously carried out.

Later in 626, Li Shimin, then in an intense rivalry with Li Jiancheng, who had been made crown prince as the oldest son, feared that Li Jiancheng was about to kill him. He submitted a secret petition to Emperor Gaozu accusing Li Jiancheng and another brother, Li Yuanji the Prince of Qin, who supported Li Jiancheng, of committing adultery with Emperor Gaozu's concubines and plotting to kill him. Emperor Gaozu, shocked by the accusations, summoned Xiao, along with Pei and Chen, to prepare to act on the accusations the next morning. Meanwhile, Li Shimin set an ambush for Li Jiancheng and Li Yuanji at Xuanwu Gate outside Emperor Gaozu's palace, and when Li Jiancheng and Li Yuanji approached Xuanwu Gate in the morning, Li Shimin killed them, and then sent his general Yuchi Jingde into the palace, claiming to be protecting Emperor Gaozu. Emperor Gaozu, realizing how serious the situation was, asked Pei, Xiao, and Chen for advice, and Xiao and Chen advised him to create Li Shimin crown prince to placate him. Emperor Gaozu did so, and two months later passed the throne to Li Shimin, who took the throne as Emperor Taizong.