Chengzu was the third emperor of the Ming dynasty. The Yongle Encyclopedia, the most voluminous reference book in China’s history, was completed during his reign. Born Zhu Di, he was the fourth son of Zhu Yuanzhang and ruled from 1402 to 1424. He was made prince of Yan in 1370, and was sent on many military campaigns in the north. Upon assumption of the throne after Zhu Yuanzhang’s death, Emperor Jianwen set out to suppress the vassal princes, taking back parts or all of their fiefdoms and power. Feeling threatened, Zhu Di launched the Jingnan Campaign in 1399. He seized the capital, Nanjing, in 1402, and usurped the throne. Starting his rule under the reign title Yongle in the following year, he started a brutal purge, killing Emperor Jianwen and his ministers as well as their relatives. Seeing his rule fairly consolidated, he reverted the fiefdoms back to the crown and continued his father’s policy of relocating the rich and powerful to tighten control over them. In the first year of his reign, he set up the Grand Secretariat, staffing it with low-ranking and inexperienced officials. He attached great importance to censorship, sending censors to check on the performance of local officials and encouraging officials to denounce each other. He cleverly exploited the eunuchs, tasking them with imperial missions, special expeditions, or supervision of the military. He also initiated the post of Grand Minister of the Imperial Household Department and created the secret service Eastern Depot to further cement his autocratic rule.
