Sejo (Korean: 세조; Hanja: 世祖; 7 November 1417 – 23 September 1468), personal name Yi Yu (이유; 李瑈), sometimes known as Grand Prince Suyang (수양대군; 首陽大君), was the seventh monarch of the Joseon dynasty of Korea. He was the second son of Sejong the Great and the uncle of King Danjong, against whom he led a coup d'état in 1453. After seizing power he killed rivals, including his brother, Grand Prince Anpyeong. During his reign, he strengthened the monarchy, reformed administration, suppressed rebellions, and led campaigns against the Jurchens. He revised land laws, promoted literature, and established court music. His Grand Code for State Administration became Joseon's foundational legal framework. Source: Wikipedia (en)