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.
Biography
Early life
Born in 1417 as the fourth child and second son of Grand Prince Chungnyeong (future King Sejong) by his primary wife, Lady Shim of the Cheongsong Shim clan (future Queen Soheon), he showed great ability at archery, horse riding and martial arts, and was also a brilliant military commander, though he never went to the battlefront himself. He also possessed musical talent, which delighted his father, who claimed that the prince could achieve many great things if he put his mind to it.[1] In 1428, he received the title Grand Prince Suyang by which he is better known.
Rise to power
Following the death of King Sejong in 1450, Suyang's ill brother, Yi Hyang (later known as King Munjong), took the throne but died two years later, and the crown passed to his 12-year-old son, Yi Hong-wi (posthumously named King Danjong).[2] The new monarch was too young to rule the nation, and the government was controlled by Chief State CouncillorHwangbo In and General Kim Jong-seo, who was the Left State Councillor. As Kim Jong-seo and his faction used the chance to extend the power of court officials against royal family members, the tension between him and Suyang greatly increased not only Suyang himself, but his younger brother, Grand Prince Anpyeong, also sought an opportunity to take control of the country.[3]
In order to court the support of the Ming dynasty, Suyang became an ambassador in 1452. He also surrounded himself with trusted allies, including his famous tactician, Han Myeong-hoe, who advised him to take over the government in a coup. In 1453, Suyang killed Kim Jong-seo and his faction, thereby taking the reins of power into his own hands. After the coup, he arrested his own brother, Grand Prince Anpyeong, first sending him into exile, then sentencing him to death.[3]
Reign
Finally, in 1455 Suyang forced the powerless king to abdicate, declaring himself the new ruler of Joseon (today known by the temple name "Sejo").[2]
After his younger brother Grand Prince Geumsung, and six scholars, including Seong Sam-mun, Park Paeng-nyeon and Yi Gae, plotted to remove him from power in an attempt to put his nephew back on the throne, Suyang demoted the former king from "King Emeritus" (Sangwang, 상왕, 上王) to "Prince Nosan" (Nosan-gun, 노산군, 魯山君) and later ordered him to commit suicide by poison.
Despite having snatched the throne from his young nephew and killing many people in the process, Sejo proved himself one of the ablest rulers and administrators in Korean history. First, he continued King Taejong's legacy of strengthening the monarchy by weakening the power of the State Council and bringing the officials directly under the king's control. He also further developed the administrative system, which had also been introduced by Taejong, enabling the government to determine exact population numbers and to mobilize troops effectively (this caused Yi Si-ae's Rebellion, which he suppressed). Just like Taejong, Sejo was a hardliner concerning foreign policy and attacked the Jurchens on the northern front in 1460 (오랑캐; 兀良哈) and 1467 (호리개; 胡里改). He also revised the land ordinance to improve the national economy and encouraged the publication of history, economy, agriculture, and religion books.
Sejo himself compiled a number of books based on his interests. One of them is Seokbosangjeol, a biography of Gautama Buddha.[4] The others are Worinseokbo (월인석보; 月印釋譜) and Yeokdaebyeongyo (역대병요; 歷代兵要). One of his crowning achievements was the cultural progress Joseon made during his reign, such as the establishment of Jongmyo court music.[1] His father, King Sejong, had always wanted to use Korean music rather than Chinese music for ancestral ritual, but conservative court officials thought that Chinese music was far superior to Korean music and stopped Sejong's efforts. However, when King Sejo rose to the throne, he modified the ritual music composed by his father and used it for royal ancestral rituals, which is now inscribed as a UNESCO Intangible Cultural Heritage for Humanity.[1]
Most importantly, he compiled the Grand Code for State Administration, which became the cornerstone of dynastic administration and provided the first form of written constitutional law in Korea.
Death
Sejo died in 1468, and the throne passed to his sickly second son, Yi Hwang (Yejong of Joseon). His tomb is known as Gwangneung (광릉) and is located in Namyangju, South Korea.
^She is only mentioned in an unofficial history (야사; 野史) called Geumgye Pildam (금계필담; 錦溪筆談) written in 1873 by Seo Yu-yeong (서유영). The sole reference at her existence in an official document is a passage from the Annals of the Joseon dynasty, where Grand Prince Suyang (as Sejo was still known at the time) is recorded as having "one son and two daughters" [Sejong Sillok, year 28].
# denotes that the king was deposed and never received a temple name.
^Those who were listed were not reigning monarchs but posthumously recognized; the year following means the year of recognition.
^Only the crown princes that didn't become the king were listed; the former year indicates when one officially became the heir and the latter one is that when one died/deposed. Those who ascended to the throne were excluded in the list for simplification.
^The title given to the biological father, who never reigned, of the kings who were adopted as the heir to a precedent king.
^The de jure monarch of Korea during the era was the Emperor of Japan, while the former Korean emperors were given nobility title "King Yi" instead.
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