Another son of Yuwen Shu, Yuwen Shiji, however, was a friend of the Tang dynasty's founder Li Yuan (Emperor Gaozu), and after Li Yuan established Tang remained an influential official.
Yuwen Shu's ancestors were originally named Poyetou (破野頭)[a] and were ethnically Xianbei.
Yuwen Shu's father Yuwen Sheng (宇文盛) was a general under Northern Zhou and eventually served as the minister of imperial clan affairs, one of the six main ministers under Northern Zhou's six-department governmental structure.
Because of his father's achievements, during the reign of Emperor Wu of Northern Zhou, he was made a mid-level governmental official.
In winter 588, when Emperor Wen launched a major attack on rival Chen dynasty, Yuwen Shu participated in the campaign, and after the generals Han Qinhu (韓擒虎) and Heruo Bi (賀若弼) crossed the Yangtze River to attack the Chen capital Jiankang, Yuwen advanced to the nearby fortress of Shitou to aid Han and Heruo.
After the completion of the campaign, in recognition of his contributions, Emperor Wen gave his son Yuwen Huaji a mid-level governmental post, while making Yuwen Shu himself the commandant at An Province (安州, roughly modern Xiaogan, Hubei).
In 604, while Emperor Wen was ill, Yuwen Shu was one of the guard commanders that Yang Guang summoned to guard Emperor Wen's vacation palace Renshou Palace (仁壽宮, in modern Baoji, Shaanxi).
Emperor Wen soon died—a death that traditional historians, while admitting a lack of direct evidence, generally believed to be a murder ordered by Yang Guang.
Emperor Yang was incensed and ordered that they be executed, but at the last minute spared them, formally awarding them to their father as slaves.
Emperor Yang's main forces put Goguryeo's key northern city Liaodong (遼東, in modern Liaoyang, Liaoning) under siege (although he was ultimately unable to capture it), but sent Yuwen with a branch army to head deep south, across the Yalu River, heading directly toward the Goguryeo capital Pyongyang.
Yuwen, Qutu, Wei Wensheng (衛文昇) and Lai Hu'er (來護兒) gave chase, catching up with Yang Xuangan at Hongnong (弘農, in modern Sanmenxia, Henan) and dealt him a final crushing blow.
Emperor Yang therefore particularly became suspicious of Li Hun's nephew Li Min (李敏), the husband of his sister Yang Lihua's daughter Yuwen Eying (宇文娥英, who was also the daughter of Northern Zhou's Emperor Xuan, as the Yang Lihua, the Princess Leping, was Emperor Xuan's wife and empress), because Li Min's nickname was "Hong'er" (洪兒), meaning "son of a flood," and Emperor Wen had long ago dreamed that a flood would overflow the capital.
Yuwen Shu then had the official Pei Renji (裴仁基) falsely accuse Li Hun of plotting treason.
The Eastern Turk leader Shibi Khan took the opportunity to launch a surprise attack against Yanmen Commandery in reprisal against various offenses by the emperor.
His Chinese wife, the princess Yicheng, secretly sent a warning of the Turkish plans to Emperor Yang, who took refuge at the commandery seat in present-day Daixian, Shanxi.
Instead, at the suggestion of his brother-in-law Xiao Yu, the emperor sought more help from Princess Yicheng, who was one of his relatives but—according to Turkish custom—was in charge of managing military affairs at home in her husband's absence.
Su, however, truthfully informed Emperor Yang that the rebellions were causing major problems for Sui rule.