Sejo of Joseon (Yi Yu)

Timeline

1. 1451–1453Hanyang · JoseonDuring King Munjong's reign (1451–1452), Grand Prince Suyang secretly recruited loyal military officers and built alliances at court and beyond, relying especially on Han Myeong-hoe and Gwon Lan. Munjong died in 1452, and the twelve-year-old Danjong ascended the throne, with regents Kim Jong-seo and Hwangbu In controlling state affairs while royal princes' power was suppressed. In the name of 'removing powerful ministers,' Yi Yu suddenly launched a coup in October 1453 (the Gyeyu year), storming the palace and killing or subsequently executing Kim Jong-seo, Hwangbu In, and their followers, seizing control of military and political centers in what is known as the Gyeyu Jeongnan.
2. 1453–1455Hanyang · JoseonAfter the Gyeyu Jeongnan, Grand Prince Suyang became Chief State Councillor, effectively controlling government as uncle while Danjong was a figurehead. In June 1455, he completed the transfer of power in the name of Danjong's 'voluntary abdication'; Danjong retired as Prince Nosan (later deposed to commoner status), and Grand Prince Suyang immediately ascended the throne as Sejo, while rewarding supporting officials as 'meritorious subjects of the Jeongnan' to further consolidate his political base.
3. 1455–1460Hanyang · JoseonIn June 1456, Jiphyeonjeon scholars led by Seong Sam-mun and Bak Paeng-nyeon conspired to assassinate Sejo during a banquet attended by the retired king Danjong and restore him to the throne. When the plot was discovered, Sejo was furious and had the six ministers, including Seong Sam-mun, executed by slow slicing, with wide-ranging purges, known as the 'Six Loyal Ministers incident.' In 1457, Sejo further demoted Danjong to commoner status, exiled him to Nyeongwol, and soon had him put to death, completely eliminating the threat of restoration. Thereafter Sejo carried out administrative reforms, abolished the Jiphyeonjeon, expanded the Seungjeongwon's authority, and began compiling the Code of Laws for Governing the Country to unify administrative law; by 1460, court order was basically stable and royal power highly centralized.