Ying Zheng came to the throne of the state Qin in 237 B.C. In 220 B.C., he conquered the other six states and built a unified, centralized country, proclaiming himself the First Emperor (Shihuang). After that, under his order, the written characters and units of measurements were standardized. Qin Shihuang dreamt to be immortal, so he sent a lot of necromancers to look for magical elixirs for him, who turned out to be cheaters. The necromancers and scholars spoke ill of him, making him so angry that he ordered to burn the books and bury the scholars alive. He also gave the order to build the Great Wall, resulting in numerous deaths of civilians. Qin Shihuang died on his fifth royal progress, succeeded by his son Huhai due to a will forged by the eunuch Zhao Gao, who became the new prime minister after plotting the death of the former one, Li Si. At the time, riots broke out all over the country, and the empire of Qin fell at its second emperor.