Thinkers Timeline

King Sejong the Great (Sejong Daewang) was the fourth king of Korea's Joseon dynasty and one of the most consequential rulers in Korean history. He is the only Korean ruler other than Gwanggaeto the Great of Goguryeo to be honoured with the title 'the Great'. His birth name was Yi Do. He was born on 15 May 1397 in Hanseong (modern Seoul), the third son of King Taejong, the third Joseon ruler. His childhood name was Won Chong. He was not the expected heir. His older brother Yangnyeong was named Crown Prince in 1404. By 1418, Yangnyeong's preference for hunting and leisure over study had led to his removal from succession. The second brother Hyoryeong took religious vows and removed himself. Yi Do, who had distinguished himself by serious study from childhood, was made Crown Prince and ascended the throne later that year at age 22, when his father Taejong abdicated in his favour. Taejong continued to influence court affairs until his death in 1422. Sejong reigned for 32 years, from 1418 to 1450. His reign is widely called the Golden Age of Joseon. He governed by Confucian principles, in which a sovereign was expected to be a scholar of broad learning and to recognise and use men of talent. In 1420 he founded the Jiphyeonjeon (Hall of Worthies), a royal research institute where scholars worked on linguistic, scientific, agricultural, medical, and astronomical projects. Under his reign Korea developed rain gauges, water clocks, sundials, advanced movable-type printing, an independent astronomical calendar based on the Seoul meridian, and many improvements to military technology. His most famous achievement was the creation of the Korean alphabet, Hangul, announced in 1443 and promulgated in 1446. He died on 8 April (or 18 May, by some calendar conversions) 1450 at age 53, by then blinded by complications of diabetes. He was buried at the Yeong Mausoleum and was succeeded by his eldest son Munjong, who reigned only briefly.