Coup
In 1167, during the royal banquet of King Uijong, Kim Don-jung, son of powerful aristocrat Kim Bu-sik(author of Samguk Sagi), burnt Jeong's long beard with candle, and made fun of him;also he mocked whole military. The incident made Jeong to have strong animosity toward aristocrats and civilian officials.
In 1170, King Uijong went to his royal villa to rest and to hold another feast, and he also held a martial arts competition. A youth soldier won the event, and was praised by the king. Then, many of king's advisers to the court and eunuchs forced General Yi So-eung, who was at his late fifties, to face the champion, who was about 20. The old general, of course, was not able to fight the young champion and fell down to the ground. Then, a young civilian official named Han Roe, insulted the general and even slapped him across his face in front of the king and many fellow soldiers. General Jeong, who could not stand the advisers' attitude anymore, knocked Han out and insulted him. The incident caused the long grivances of military to explode; young soldiers, notably Colonels Yi Ui-bang, Yi Go and Chae Won, urged Jeong to launch a coup d'état against the entire government and the king, who favored civilian officials over army. Jeong first ignored their opinion but later agreed to revolt against the government. With his order in the name oh commander-in-chief, the whole army rebelled against the king and his advisers. Almost all of advisers, including Kim Don-jung and Han Roe, were killed and King Uijong was overthrown;then he set up a puppet king, King Myeongjong, beginning the 100-year military rule of Korea.
Read more about this topic: Jeong Jung-bu