Emperor Hui of Jin

Emperor Hui of Jin (simplified Chinese: 晋惠帝; traditional Chinese: 晉惠帝; pinyin: Jìn Huì Dì; Wade–Giles: Chin Hui-ti; 259 – 8 January 307), personal name Sima Zhong (司馬衷), courtesy name Zhengdu (正度), was the second emperor of the Western Jin dynasty. Emperor Hui was a developmentally disabled ruler, and throughout his reign, there was constant internecine fighting between regents, imperial princes (his great-uncle, half-brothers and distant cousins), and his wife Empress Jia Nanfeng for the right to control him (and therefore the imperial administration), causing great suffering for the people and greatly undermining the stability of the Western Jin dynasty, eventually leading to rebellions of the Five Barbarians that led to Jin's loss of northern and central China and the establishment of the competing Sixteen Kingdoms. He was briefly deposed by his granduncle Sima Lun, who usurped the throne himself, in February 301, but later that year was restored to the throne and continued to be the emperor until January 307, when he was poisoned, likely by his last regent Sima Yue.

Life prior to ascension

Sima Zhong was born to Sima Yan and his wife Yang Yan in 259 AD, while Sima Yan was still the assistant to his father, the Cao Wei regent Sima Zhao. He was their second son, but after the early death of his older brother Sima Gui (司馬軌), he became the oldest surviving son. It is not known when his developmental disabilities became apparent. In any case, after Sima Zhao died in September 265, and Sima Yan subsequently forced the Cao Wei emperor Cao Huan to abdicate to him in February 266, he made the nine-year-old (by East Asian reckoning) Prince Zhong crown prince in 267 AD.

As Crown Prince Zhong grew in age, his developmental disabilities became clear to his parents and the imperial officials alike. He learned how to write and speak, but appeared to be unable to make logical decisions on his own at all. Once, when he heard frogs croaking, he asked, in all seriousness, "Do they croak because they want to, or because the government ordered them to?" Several times, officials reminded Emperor Wu of this, but Emperor Wu, not realizing the extent of Crown Prince Zhong's disability, resisted the implicit calls for him to be replaced. Indeed, because Emperor Wu was concerned that many officials were impressed with his talented younger brother, Sima You the Prince of Qi and might want Prince You to replace him instead, he eventually had Prince You sent to his principality, and Prince You died in anger in April 283.