During his rule, Goryeo faced many hardships, including the Mongol invasion of Korea, which led to the relocation of the capital from Gaegyeong to Ganghwa Island.
Ch'oe U's soldiers practiced combat with flags and drums from Seonjukkyo to Sunginmun when the Khitans invaded, indicating his preparedness to maintain power.
King Huijong even requested Ch'oe U to write the screen texts for Seongyeongjeon and Daegwanjeon, where envoys from the Jin dynasty were received.
He then systematically removed critical figures from his father's administration, including Kŭm Ŭi (금의; 琴儀), Chŏng Pang-bo (정방보; 鄭邦輔), and Mun Yu-p'il (문유필; 文惟弼), under the pretext of eradicating corruption.
[1][2] When Ch'oe U ascended to power in 1219, his official position was merely a vice commissioner of the Security Council (추밀원부사; 樞密院副使; ch'umilwŏnpusa).
By the end of the following year, he had been promoted to Assistant Executive in Political Affairs (참지정사; 參知政事; ch'amji chŏngsa).
Remarkably, despite holding exclusive power for almost 30 years after that, these were his last official positions, signifying that his authority was established independently of the formal bureaucratic structure.
[1][2] In 1221, he became assistant executive in political affairs (참지정사; 參知政事; ch'amji chŏngsa), the minister of personnel and war (이병부상서; 吏兵部尙書; ibyŏngbu sangsŏ), and superintendent of the Censorate, thereby solidifying his position as ruler.
In 1223, he contributed over 300 ŭnbyŏng and 2,000 sŏk of rice, mobilized his private soldiers to repair the outer walls of Gaeseong, and created a 13-story pagoda and flower vases with 200 kŭn of gold, which he enshrined at Heungwangsa Temple (興王寺).
In 1229 (the 16th year of King Gojong's reign), he forcibly confiscated over a hundred neighboring houses to create a significant polo ground.
In 1231, upon the death of his wife, Lady Chŏng, her funeral followed the precedent set by Queen Sundeok, the consort of King Yejong.
The extravagance displayed by officials competing to offer lavish tributes caused a significant rise in market prices.
[1][2] Meanwhile, in Ganghwa, Kim Yak-sŏn prospered politically, even marrying his daughter to the crown prince, the future king Wonjong.
However, jealousy from his wife over his interactions with other women led to a complaint to her father, Ch'oe U, resulting in Kim Yak-sŏn's elimination.
Eventually, Ch'oe U, advised by Pak Hwŏn (박훤; 朴暄) and Song Kuk-ch'ŏm (송국첨; 宋國瞻), confiscated his sons' ill-gotten wealth and imprisoned their followers.
Ch'oe U confided this prediction to his close aide Kim Hŭi-je (김희제; 金希磾) to gauge his reaction, but he became furious when it was met with indifference.
Ch'oe U sometimes used his wealth for public works, such as repairing the outer walls of Gaegyeong or donating rice to the Yanghyeon Foundation (養賢庫).
For instance, once he suffered from severe leg swelling, everyone from high-ranking officials to lower-level clerks offered prayers and composed writings for his recovery, causing a paper shortage in the capital.
Despite the efforts of many physicians, it was the wife of an official named Im Chŏng (임정; 林靖), who came from a family of doctors who successfully treated him with an herbal plaster.
During Ch'oe U's rule, internal and external instability led to the decline of official military forces, resulting in a rise in banditry.
This group later split into the Left and Right Byeolcho and, along with the Shin'ui Army (神義軍), formed the Sambyeolcho (三別抄), which served as the military foundation for the Ch'oe regime.
Chamber of Scholarly Advisors was a group of literati established at Ch'oe U's residence, divided into three shifts to serve continuously.
[1][2] Despite his initial efforts to gain popular support, his later years were marked by tyranny and extravagance, leading to public resentment.
During the Mongol invasions and the subsequent relocation of the capital to Ganghwa Island, Ch'oe U seized over a hundred carts to transport officials' salaries.
He constructed a high pavilion draped with silk and brocade curtains, where swings adorned with intricate patterns were hung.
He held 26 official titles, including Grand Master of the Palace with Golden Seal and Purple Ribbon (금자광록대부; 金紫光祿大夫; kŭmja kwangnok taebu), acting grand preceptor (수태사; 守大師; su t'aesa), Kaebu ŭidong samsa (개부의동삼사; 開府儀同三司), secretariat director (중서령; 中書令; chungsŏryŏng), supreme pillar of state (상주국; 上柱國; sangjuguk), supreme general (상장군; 上將軍; sangchanggun), prime historiographer (감수국사; 監修國史; kamsuguksa), superintendent of the Censorate, Jin Yang-gun Gae-guk-gong (晋陽郡開國公), and others.
[1][2] King Gojong promptly appointed Ch'oe Hang to high offices similar to those initially held by his father and soon after made him special commissioner of the Directorate-General for Policy Formulation, formalizing his rule.