Sejong the Great

Born in 1397, the third son of the future King Taejong, Sejong was considered more gifted than his troubled older brother, the crown prince. In mid-1418, the crown prince was deposed and Sejong was elevated; months later, his father abdicated and Sejong took the throne at twenty-one. His reign became a high-water mark: he reestablished the Hall of Worthies in 1420, a research body that produced Korea's first native calendar, a 365-volume medical encyclopedia, and key agricultural texts. He led a successful invasion of Tsushima Island in 1419, then brokered decades of peace with Japan; he pushe…