Sejo Usurpation (世祖簒位) was a coup that took place in the 3rd year of Danjong of Joseon (1455), in which the royal Grand Prince Suyang of Joseon drove out his nephew Danjong and seized the throne. After seizing power through the Gyeyu Incident, Grand Prince Suyang, Han Myeong-hoe, Kwon Lam, Sin Sukju and others deposed Danjong and enthroned Grand Prince Suyang (Sejo), the king's uncle. Depending on one's viewpoint, it is also called the Sejo Restoration (世祖反正) or the Danjong Deposition Incident. It is also named after the year in which it occurred as the Eulhae Restoration (乙亥反正) or Eulhae Jeongsa (乙亥靖社).
Background
After the deaths of King Sejong and King Munjong, officials and maternal relatives gained power in place of the young Danjong. Grand Princes Suyang, Anpyeong and others, who resented this, rose to prominence and used the Gyeyu Incident as a pretext for their restoration.
When Danjong ascended the throne, he was only twelve years old. In accordance with the last command of his father and predecessor, King Munjong, Left State Councilor Kim Jong-seo, Chief State Councilor Hwangbo In, Right State Councilor Jeong Bun and others assisted him, and scholars of the Hall of Worthies also gave their support.
However, Danjong's grandfather, King Sejong, had eighteen sons. Among them, Grand Prince Suyang, the second son of Sejong, who together with Grand Prince Yangnyeong and Grand Prince Hyoryeong stood at the head of the royal kinsmen, was a man of extraordinary ambition and ability. At this time all the grand princes competed to take in guests to expand their power, and military men gathered around Grand Prince Suyang.
Many scholars of the Hall of Worthies gathered around Grand Prince Anpyeong, and Grand Prince Suyang also worked to win over the scholars of the Hall of Worthies. As a result, Sin Sukju, Jeong Chang-son, Kim Jil, Jeong Inji and others sided with Grand Prince Suyang.
Course of events
Having eliminated the factions of Kim Jong-seo and Hwangbo In and the relatives of Grand Prince Anpyeong through the Gyeyu Incident, Grand Prince Suyang became Chief State Councilor and regent. Sin Sukju, Han Myeong-hoe, Kwon Lam and others then had Danjong abdicate the throne to Grand Prince Suyang in the form of an abdication.
Gyeyu Incident
Through his adviser Kwon Lam, Grand Prince Suyang obtained Han Myeong-hoe, who was then serving as an official at Gyeongdeok Palace, and through Han Myeong-hoe he won over more than thirty capable military men, including Hong Dal-son and Yang Jeong, and watched for an opportunity. Han Myeong-hoe, a man who could read the times, became a strategist for Grand Prince Suyang. Kwon Lam and Han Myeong-hoe, who were in unfortunate circumstances, argued for the justification of a coup by citing the decline of royal authority, the overwhelming power of the ministers and social disorder.
First, in the tenth lunar month of 1453 (1st year of Danjong), Grand Prince Suyang sought to eliminate Kim Jong-seo, the most resourceful and brave of the three lords (公) who assisted Danjong. He led armed men to attack Kim Jong-seo's house and killed him, and then reported to the king that Kim Jong-seo had plotted rebellion and that, since the matter was urgent, there had been no time to inform the king in advance. Then, borrowing the king's authority, he summoned the ministers and, as planned in advance, executed at the palace gate the leading opposition officials, including Chief State Councilor Hwangbo In, Minister of War Jo Geuk-gwan, and Vice Minister (贊成) Yi Yang. He also exiled Right State Councilor Jeong Bun, as well as Jo Su-ryang (younger brother of Jo Geuk-gwan), and later had them executed. Meanwhile, the heads of Kim Jong-seo and the others were hung on display, their descendants were executed, and, on the charge that Grand Prince Anpyeong had colluded with Kim Jong-seo and others, he was exiled to Ganghwa Island and later ordered to commit suicide.
Abdication
Having gained real power through the coup, Grand Prince Suyang at once concurrently held the posts of Chief State Councilor, Minister of Personnel and Minister of Justice, and Commander-in-chief of the Military (內外兵馬都統使), thereby seizing both civil and military power. He appointed Jeong Inji as Left State Councilor and Han Hwak, father-in-law of his eldest son, Prince Dowon, as Right State Councilor. He also had the Hall of Worthies write a proclamation praising Grand Prince Suyang, and received it in the king's name.
When the danger to Grand Prince Geumseong's life arose because of Grand Prince Suyang's power and authority, Danjong realized that he had no choice. In the intercalary sixth month of 1455 (3rd year of Danjong), he conveyed his intention to abdicate to Grand Prince Suyang and personally handed over the Great Seal (大寶). The one who succeeded Danjong was thus Sejo.
Danjong Restoration Movement
The abdication plan was pursued in utmost secrecy by Kwon Nam, Jeong Inji and others. Although it took the form of a voluntary transfer, it was in fact a seizure of the throne through a scheme. Against this action, Seong Samun, who was especially trusted by King Sejong as a scholar of the Hall of Worthies, Military Vice Commander (Hyeongjo chamchanpan) Park Paengnyeon, Director of Academic Affairs (直提學) Yi Gae, Vice Minister of Rites Ha Wi-ji, Sayesa (司藝) Yu Seong-won, Seong Samun's father Seong Seung, Provincial Military Commander Jo Sung-mun, Yu Eung-bu, and Military Staff Officer Park Simmun, plotted to restore Danjong, who was living at Sugang Palace as Retired King, and to purge the rebellious faction, and they watched for an opportunity.
They planned to act in 1456 (2nd year of Sejo), in the sixth lunar month, during a banquet for Ming envoys at Changdeok Palace. However, when the plan went awry, Kim Jil and Jeong Chang-son, seeing that the situation was turning against them, informed on the plot. Sejo immediately subjected Seong Samun and the others to brutal torture, but none of them yielded. Seong Samun, Park Paengnyeon, Yu Eung-bu and Yi Gae were executed by burning (灼形, jeokdokgil) and other punishments. Ha Wi-ji was also executed by slaughter, and Yu Seong-won killed himself at his home. These men are called the Six Martyrs (Saeyuksin). Those implicated in the affair, including Kwon Ja-sin and Kim Mun-gi, about seventy people in all, were also punished.
Afterwards, Sejo charged that the retired king Danjong had also been involved in the affair, demoted him to Nosan-gun (Lord of Nosan), and had him exiled to Yeongwol under escort of fifty soldiers. He posthumously deposed Danjong's mother, Queen Hyeonduk, and made her a commoner. He also exiled Sejo's younger brother, Grand Prince Geumseong, to Sunheung.
Then, in the ninth month, Grand Prince Geumseong, together with the magistrate (府使) Yi Bo-heum, plotted to restore Danjong and tried to raise troops by circulating a proclamation (檄文) among the people of Yeongnam. However, a denunciation was lodged and the plot was exposed. Grand Prince Geumseong was imprisoned in Andong, and Yi Bo-heum and many other people of Yeongnam were executed. Meanwhile, Prince Hannam and Prince Yeongpung, sons of King Sejong, were also exiled far away, and the title of king (君) was removed from Nosan-gun, reducing him to commoner status. Thereupon, Chief State Councilor Jeong Inji, Left State Councilor Jeong Chang-son, Minister of Personnel Han Myeong-hoe, Left Assistant State Councilor Sin Sukju and others insisted that Nosan-gun (Danjong) and Grand Prince Geumseong be punished further. Sejo finally had Grand Prince Geumseong ordered to commit suicide, and also killed Danjong, who was then only seventeen years old.
Impact
As the first deposition of a king in the Joseon period, it influenced the Jungjong Restoration, the Injo Restoration, Yi Gwal's Rebellion, and the Attempted poisoning of King Gyeongjong. The usurpation of Sejo, that is, the deposition of Danjong, directly caused later literary purges (sahwa), and it also shocked scholars and literati greatly, becoming one of the causes of enduring factional conflict and hostility.
References
This article contains text based on the article "Formation of Joseon Yangban Society" from the Global World Encyclopedia, distributed by Daum Communications (now Kakao) under the GFDL or CC-SA license.