Taejo of Joseon

Born Yi Sŏnggye on 4 November 1335, he rose through Goryeo's military ranks before deciding the kingdom itself had to go. In 1392 he overthrew the Goryeo regime and founded Joseon, taking the throne as its first monarch. He kept the old guard in place - the same ruling families, the same officials, no purges, no institutional overhaul - and mended fences with Japan while smoothing relations with Ming China. Six years later, a power struggle between his sons forced him to abdicate. He later changed his personal name to Yi Tan, and after Korea became an empire, was posthumously elevated to Emperor Ko. He died 27 June 1408.