Emperor Jianwen of Jin - During Emperor Mu's Reign

During Emperor Mu's Reign

In 344, another nephew of Sima Yu, Emperor Kang (Emperor Cheng's younger brother), died, and was succeeded by his infant son Emperor Mu. Emperor Mu's mother Empress Dowager Chu became regent, but she largely followed the advice of prime minister He Chong (何充). As it was customary, at this point of Jin history, for there to be two prime ministers, He Chong recommended Empress Dowager Chu's father Chu Pou (褚裒), who declined and recommended Sima Yu instead. He Chong and Sima Yu thus shared the prime minister responsibilities until He Chong's death in 346. He Chong was replaced by Cai Mo (蔡謨).

In 347, after the ambitious general Huan Wen, without the imperial government's approval, carried out a campaign against and destroyed Cheng Han, annexing Cheng Han territory to Jin, the imperial government became apprehensive that Huan would use this opportunity to take over. Sima Yu thus invited the official Yin Hao, who was considered able, to join him and Cai in making important decisions, to counter Huan's influence. In 350, after Cai had repeatedly declined greater honor conferred him by the emperor, Yin accused Cai of disrespecting imperial authority and had him removed, seizing more power than he had before.

In 348, Sima Yu's heir apparent Sima Daosheng (司馬道生), who was described as careless and frivolous, was accused of unspecified crimes, and he was deposed and imprisoned, and died in imprisonment. Sima Yu's wife and Sima Daosheng's mother, Princess Wang Jianji (王簡姬), also died in distress. (She might have also been imprisoned prior to her death) His other sons, one by Princess Wang and three by various concubines, died early, and he was left without an heir, and his concubines were not conceiving any more. He retained a magician to look at his concubines to see which one could conceive an heir, and the magician looked at all of them and opined that none was destined to give him an heir—but then he saw a dark-skinned maid who was working with textiles, who was derogatorily referred to as a Malay, named Li Lingrong, and he, in surprised, yelled out, "She is the one!" Sima Yu therefore took her as a concubine, and she bore him two sons -- Sima Yao in 352 and Sima Daozi in 353. Sima Yao was subsequently named heir apparent.

Around the new year 352, Huan, impatient after his requests to advance north in light of Later Zhao's collapse were being rebuffed by Sima Yu and Yin, who were concerned about his expanding power, and mobilized his troops and gestured as if he were about to attack the capital. Yin was shocked, and initially considered either resigning or send the imperial banner of peace (Zouyu Fan, 騶虞幡) to order Huan to stop. After advice from Wang Biaozhi (王彪之), however, he instead asked Sima Yu to write a carefully worded letter to Huan, persuading Huan to stop.

After Yin himself launched unsuccessful northern campaigns in 352 and 353—the latter at great loss of life and property—Huan submitted a petition accusing Yin of crimes. The imperial government, led by Sima Yu, felt compelled to depose Yin in 354. From that point on, Sima Yu became the sole prime minister, although he was often forced to submit to Huan's wishes on important matters. Later in 354, Huan himself launched a campaign north against Former Qin, one of the successor states to Later Zhao, but after initial successes, he was forced to withdraw as he hesitated at attacking Former Qin's capital Chang'an and ran out of food supplies.

In 358, Sima Yu offered to resign and return all authority to Emperor Mu. Emperor Mu declined.

In 361, Emperor Mu died without a son, and by order of Empress Dowager Chu, his cousin Sima Pi the Prince of Langye ascended the throne as Emperor Ai. Sima Yu continued in his post as prime minister.