Sima Daozi
In 399, Sima Daozi was afflicted with illnesses and alcoholism, and one day, while Sima Daozi was drunk, Sima Yuanxian had Emperor An issue an edict removing Sima Daozi from his post as prime minister and transferring the authority to Sima Yuanxian. After he came to, Sima Daozi became furious at his son, but could do nothing. From this point on, while Sima Daozi was titular regent, Sima Yuanxian was the actual regent. He greatly trusted the strategist Zhang Fashun (), and also introduced many trusted associates into the administration. While he appeared to have some abilities, he also was, according to traditional historians, wasting the government's money in luxury and not paying attention to the burdens of the people. Late in 399, Sun En, seeing how the only province remaining under Jin imperial government's actual control—Yang Province (揚州, modern Zhejiang and southern Jiangsu) -- had been mismanaged by Sima Yuanxian, launched a major attack from Zhoushan Island, briefly taking over nearly all of Yang Province and advancing on the capital Jiankang (modern Nanjing, Jiangsu). Sun's rebellion was soon put down by Liu Laozhi, and Sun fled back to Zhoushan (but would remain a menace for several years), but Yang Province had been laid to waste. Despite this, Sima Yuanxian grew increasingly extravagant and arrogant.