Emperor Wu was also known for his extravagance and sensuality, especially after the unification of China; legends boasted of his incredible potency among ten thousand concubines.
His generosity and kindness undermined his rule, as he became overly tolerant of the noble families' (世族 or 士族, a political/bureaucratic landlord class from Eastern Han to Tang dynasty) corruption and wastefulness, which drained the people's resources.
Further, when Emperor Wu established the Jin Dynasty, he was concerned about his regime's stability, and, believing that the predecessor state, Cao Wei, had been doomed by its failures to empower the princes of the imperial clan, he greatly empowered his uncles, his cousins, and his sons with authority, including independent military authority.
[5] After his father was created the Duke of Jin on 9 December 263 in light of the army's conquest of Shu Han, he was named heir.
Emperor Wu immediately sought to avoid what he saw as Cao Wei's fatal weakness—lack of power among the imperial princes.
In February 266, immediately after taking the throne, he made princes of many of his uncles, cousins, brothers, and sons, each with independent military commands and full authority within their principalities.
In 271, Jiao Province (交州, modern northern Vietnam), which had paid allegiance to Jin ever since the start of his reign, was recaptured by Eastern Wu.
In 272, the Eastern Wu general Bu Chan, in fear that Sun Hao was going to punish him on the basis of false reports against him, tried to surrender the important city of Xiling (西陵, in modern Yichang, Hubei) to Jin, but Jin relief forces were stopped by the Eastern Wu general Lu Kang, who then recaptured Xiling and killed Bu.
In light of these failures, Yang took another tack—he started a détente with Lu and treated the Eastern Wu border residents well, causing them to view Jin favorably.
When Emperor Wu ascended the throne in February 266, he honored his mother Wang Yuanji as empress dowager.
In 266, he also honored his aunt Yang Huiyu (Sima Shi's wife) an empress dowager, in recognition of his uncle's contributions to the establishment of the Jìn Dynasty.
In 267, he made her oldest living son, Sima Zhong crown prince—based on the Confucian principle that the oldest son by an emperor's wife should inherit the throne—a selection that would, however, eventually contribute greatly to political instability and the Jin Dynasty's decline, as Crown Prince Zhong appeared to be developmentally disabled and unable to learn the important skills necessary to govern.
He looked most attentively at the daughters of high officials, but he also ordered that no marriages take place across the empire until the selection process was done.
After Emperor Wu became well, he divested some military commands from officials that he thought favored Prince You, but otherwise took no other punitive actions against anyone.
After the fall of Eastern Wu, Emperor Wu ordered that provincial governors no longer be in charge of military matters and become purely civilian governors, and that regional militias be disbanded, despite opposition by the general Tao Huang and the key official Shan Tao.
This would also eventually prove to create problems later on during the upheaval of the Five Barbarians, as the regional governors were not able to raise troops to resist quickly enough.
[citation needed] SGZ has: "On the day renchen (September 7), the Crown Prince of Jin, Sima Yan, succeeded to his enfeoffment and inherited his rank; he assumed the Presidency of the myriad officials and had gifts and documents of appointments conferred upon him, all in conformity with ancient institutions".