How did the official historian Yuwen Cheng die?

Yuwen Cheng was one of the founding emperors of the Northern Zhou Dynasty during the Northern and Southern Dynasties. The cause of his death was controversial in history. According to the historical records of Yuwen Yong, Emperor Wu of the Northern Zhou Dynasty, Yuwen Cheng was appointed as the crown prince after the establishment of the Northern Zhou Dynasty and became the emperor after Yuwen Jue inherited the throne. After the throne was stabilized, Yuwen Cheng began to consolidate his position and strengthen the central power and military control. At the same time, he vigorously expanded his territory and annexed neighboring countries. However, in the process of attacking Liaodong, Yuwen Cheng was unfortunately killed by the enemy. The specific cause of death was not recorded in the history books. One theory was that Yuwen Cheng died of exhaustion while attacking Liaodong. Another theory was that Yuwen Cheng died of illness after being injured in battle and could not be treated in time. No matter what, the cause of Yuwen Cheng's death had not been fully proven, and it had become a controversial topic in history.