Jeongjo of Joseon
Early life

He was the son of Crown Prince Sado (who was put to death when Jeongjo was 11 by his father, King Yeongjo) and Lady Hyegyeong (who wrote an autobiography, The Memoirs of Lady Hyegyeong detailing her life as the ill-fated Crown Princess of Korea). His elder brother Crown Prince Uiso died in infancy. His mother Lady Hyegyeong's collection of memoirs serves as a significant source of historical information on the political happenings during the reigns of King Yeongjo (her father-in-law), King Jeongjo (her son), and King Sunjo (her grandson).

In 1762, his father, Crown Prince Sado, was executed (by imprisonment in a rice chest) by King Yeongjo (Crown Prince Sado's father and Prince Yi San's grandfather) after long conflicts and Sado's years of mental illness. Crown Prince Sado opposed the ruling Noron party. He started to hate the parties of Joseon. Eight years later Yi San asked to visit Sado's living quarter but his Grandfather King Yeongjo refused. So he refused to attend Crown Prince Sado's funeral. On 21 February 1764, Yi San became the adoptive son of Crown Prince Hyojang and Princess Consort Hyosun by the order of King Yeongjo. Crown Prince Hyojang was the elder half-brother of his father, Crown Prince Sado. Crown Prince Hyojang though, had died during his childhood. King Yeongjo made Yi San a part of Hyojang's family because he was concerned that Yi San, who was Sado's son and successor, would be opposed. The Noron faction protested Yi San's legitimacy as the royal successor under the claim that Yi San was the 'Son of a prisoner' or 'Son of a madman' and thus ineligible to succeed the throne. This was a major source of vexation for King Yeongjo for an extended period.

After 1762 to 1777, some members of Noron attempted to depose Jeongjo for his relation to Crown Prince Sado and open the path of succession for his half-brothers Prince Eunjeon, Prince Euneon and, Prince Eunshin. His grand uncle Hong In-han and Jeong Hu-gyeom, adopted son of Princess Hwawan, were amongst them.

When he was the Crown Prince, King Jeongjo met Hong Guk-yeong (홍국영; 洪國榮), a controversial politician who first strongly supported Jeongjo's accession and toiled to improve the king's power, but ended up being expelled because of his desire and ambition for power. Another helper was Kim Jong-su (김종수; 金鍾秀), despite being a member of Noron.

In 1775, one year before King Yeongjo's death, King Jeongjo was appointed regent. However, King Yeongjo did not give him any military power.
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