Role in coups against Yang Jun and Sima Liang
Empress Dowager Yang's father Yang Jun initially served as Emperor Hui's regent. Knowing Empress Jia to be treacherous, he set up a system where edicts signed by Emperor Hui had to be co-signed by Empress Dowager Yang as well, to prevent Empress Jia from interfering. For a while, her influence was limited to matters inside the palace—and after her stepson Prince Yu was created crown prince, she often blocked Consort Xie from having access to her son.
Empress Jia was not happy about having little input in governance, however. She therefore conspired with the eunuch Dong Meng (董猛) and the generals Meng Guan (孟觀) and Li Zhao (李肇) against the Yangs. She tried to include Emperor Hui's granduncle Sima Liang, the most respected of the imperial princes, into the conspiracy, but Sima Liang declined; instead, she persuaded Emperor Hui's brother, Sima Wei the Prince of Chu, to join her plan. In 291, after Sima Wei returned to Luoyang from his defense post (Jing Province (荊州, modern Hubei and Hunan)) with his troops, a coup went into progress.
Empress Jia, who had her husband easily under her control, had him issue an edict declaring that Yang Jun had committed crimes and should be removed from his posts. It also ordered Sima Wei and Sima Yao (司馬繇) the Duke of Dong'an to attack Yang's forces and defend against counterattacks. Quickly, it became clear that Yang was in trouble. Empress Dowager Yang, trapped in the palace herself, wrote an edict ordering assistance for Yang Jun and put it on arrows, shooting it out of the palace. Empress Jia then made the bold declaration that Empress Dowager Yang was committing treason. Yang Jun was quickly defeated, and his clan was massacred in April. Empress Dowager Yang was deposed and imprisoned (and would die in 292 in imprisonment). Sima Liang was recalled to serve as regent, along with Wei Guan. After that time, Empress Jia became more free involved in the management of the empire.
Sima Liang and Wei tried to get the government on track, but Empress Jia continued to interfere with management of daily governmental matters. They also became concerned about the violent temper of Sima Wei and therefore tried to strip him of his military command, but Sima Wei persuaded Empress Jia to let him keep his military command. Sima Wei's assistants Qi Sheng (岐盛) and Gongsun Hong (公孫宏) thereafter falsely told Empress Jia that Sima Liang and Wei planned to depose the emperor. Empress Jia, who had already resented Wei for having, during Emperor Wu's reign, suggested that he change his heir, and therefore resolved to undergo a second coup.
In the summer of 291, Empress Jia had Emperor Hui personally write an edict to Sima Wei, ordering him to have Sima Liang and Wei removed from their offices. His forces thereby surrounded Sima Liang and Wei's mansions, and while both men's subordinates recommended resistance, each declined and was captured. Against what the edict said, both were killed—Sima Liang with his heir Sima Ju (司馬矩) and Wei with nine of his sons and grandsons. Qi then suggested to Sima Wei to take the chance to kill Empress Jia's relatives and take over the government, but Sima Wei hesitated—and at the same time, Empress Jia came to the realization that killing Sima Liang and Wei, if it had been realized that she intended it, could bring a political firestorm and that also Sima Wei would not be easily controlled. She therefore publicly declared that Sima Wei had falsely issued the edict. Sima Wei's troops abandoned him, and he was captured and executed. Sima Liang and Wei were posthumously honored. Through this, Empress Jia could finally take all the power herself, and rule with the emperor as her puppet. After this point on, Empress Jia became the undisputed power behind the throne for several years.
