claim: Sejong the Great died in 1430.
evidence: Sejong the Great -LRB- -LSB- se.dʑoŋ -RSB- ; 15 May 1397 - 8 April 1450 -RRB- was the fourth king of Joseon-dynasty Korea .. Joseon. Joseon. He was the third son of King Taejong and Queen consort Min .. King Taejong. Taejong of Joseon. Taejong. Taejong of Joseon. He was designated as heir-apparent , Crown Prince , after his older brother Jae was stripped of his title .. Crown Prince. Styles and titles in the Joseon Dynasty. He ascended to the throne in 1418 .. During the first four years of his reign , Taejong governed as regent , after which his father-in-law , Sim On , and his close associates were executed .. Taejong. Taejong of Joseon. Sim On. Sim On. Sejong reinforced Confucian policies and executed major `` legal amendments '' .. Confucian. Korean Confucian. He also created the Korean alphabet Hangul , encouraged advancements of scientific technology , and instituted many other efforts to stabilize and improve prosperity .. Hangul. Hangul. He dispatched military campaigns to the north and instituted the Samin Policy to attract new settlers to the region .. To the south , he subjugated Japanese raiders and captured Tsushima Island .. Tsushima Island. Tsushima Island. During his reign from 1418 to 1450 , he governed from 1422 to 1442 and governed as regent with his son Crown Prince Munjong until his death in either 1442 or 1450 .. Crown Prince. Styles and titles in the Joseon Dynasty. Munjong. Munjong of Joseon. Although the appellation `` the Great ''  /  '' '' was given posthumously to almost every ruler of Goryeo and Joseon , this title is usually associated with Gwanggaeto and Sejong .. Joseon. Joseon. Goryeo. Goryeo. Gwanggaeto. Gwanggaeto