Qin Er Shi
Zhao Gao started his career under Qin Shi Huang as Prefect of the Office for Imperial Carriages (中車府令), an official in charge of managing the palace horse-drawn carriages. During this period of time, he also served as an attendant to Huhai, Qin Shi Huang's youngest son, and tutored him in the laws of the Qin Empire. In 210 BC, after Qin Shi Huang died in Shaqiu (沙丘; south of present-day Dapingtai Village, Guangzong County, Hebei), Zhao Gao and Li Si, the Chancellor, secretly changed the emperor's final edict, which named Fusu, the crown prince, the heir to the throne. In the falsified edict, Fusu was ordered to commit suicide while Huhai was named the new emperor. After Huhai was enthroned as Qin Er Shi, he promoted Zhao Gao to Prefect of the Gentlemen of the Palace (郎中令), an official post whose duties included managing the daily activities in the imperial palace. Zhao Gao, who was highly trusted by Qin Er Shi, instigated the emperor to exterminate his own siblings to consolidate power, and used the opportunity to eliminate his political opponents such as Meng Tian and Meng Yi. He also framed Li Si for treason and had Li Si and his entire family executed, after which he replaced Li Si as Chancellor and monopolised state power. In 207 BC, when rebellions broke out in the lands east of Hangu Pass, Zhao Gao became worried that Qin Er Shi would blame him, so he launched a coup in Wangyi Palace (望夷宮; in Xianyang, near present-day Xi'an, Shaanxi) and assassinated the emperor. Following Qin Er Shi's death, Zhao Gao installed Ziying, Fusu's son (allegedly; there is no firm consensus on what Ziying's relationship to the Qin royal family really is), on the throne. Ziying sent Han Tan (韓談), a eunuch, to assassinate Zhao Gao.