The political revolt from the 34th year(1601) of King Seonjo's era was caused by Kil Oon-jeol and So Deok-u's attempted coup d'etat in Jeju island. So Deok-u went to the island under the guise of purchasing horses. He was in frequent contact with the government office and various influential people, and he used these connections to persuade people to his side. People of various social strata, including general Moon Chung-gi, as well as scholars, conscripted soldiers, infantrymen, navy men, warning light men, guarantors of a soldier, petty town officials and servants joined his party. There was Moon Chung-gi in the party who was a high ranking official and carried considerable influence in Jeju island.
So Deok-u was making good progress in preparing the coup when he called Kil Oon-jeol in to the island. Kil Oon-jeol's participation accelerated the pace of the preparation. They planned to kill a governor of Jeju and officials from Seoul before advancing on Seoul with their army. Kil Oon-jeol swayed his followers by promising support of the Jeonla naval force commander and troops in Kyeongsang Province. He further proclaimed that boat reinforcements were to arrive imminently in Jeju to help their revolt.
Army recruitment hit a snag, however, and the original date of revolt had to be postponed. The leaders had a meeting called 'Chungammyojeong' and decided carry out the coup d'etat on 6th July, 1601. However, in an unexpected betrayal, Kil Oon-jeol revealed the plan to a government office while his followers were preparing for the revolt.
The Government launched an investigation into the conspiracy and interrogated So Deok-u, Moon Chung-gi and about 20 other leaders of the revolt. Kil Oon-jeol was the whistleblower as well as the mastermind behind the plot. So, the matter of his punishment caused much controversy. A compromise was ultimately reached by sentencing him to death but sparing his family from involvement in the conspiracy. However, harsher punishments were handed out to other participants, like So Deok-u, Hye Su, Moon Chung-gi and Kang U-jeong, who were hacked into pieces. The government dispatched Kim Sang-heon as a royal emissary of Jeju to close the investigation and to comfort people on the island.
Although the conspiracy was planned jointly by two groups, those from the mainland including Kil Oon-jeol and So Deok-u and those from Jeju Island, including Moon Chung-gi, Hong Kyeong-won, these two groups had different interests in the matter and lacked mutual trust. Kil Oon-jeol testified that he blew the whistle on the plan because he thought he would not be able to take military power from the Jeju people even if the revolt had been successful.
Kil Oon-jeol and So Deok-u's intentions were to advance into to the mainland and to seize political authority in the south eastern part of the country and Seoul through the revolt, but Jeju people like Moon Chung-gi were not concerned about going into the mainland. Their motivation in joining the revolt was to rid Jeju of its despotic governor and to escape from a heavy burden of military service, labor and tax. As a result of these disparate aims, the groups could not achieve harmony with each other and were forced to make concessions in their original plans. Because of this process, Kil Oon-jeol lost confidence in the success of the revolt. So, Kil Oon-jeol's betrayal destroyed the union of the two groups, who had been operating tenuously under different political interests, and caused the ultimate failure of the revolt.
