Gang Jo's Coup

Overview

Gang Jo's Coup was an incident in which, in the second lunar month of 1009 (12th year of King Mokjong), Gang Jo, Commissioner of Military Affairs of the Northwestern Region, led his troops into Gaegyeong, deposed King Mokjong, and enthroned Grand Prince Wang Sun (King Hyeonjong). Gang Jo then killed King Mokjong at Jeoksung County while the former king was on his way into exile. The following year, the Khitan launched their Second Invasion, claiming to punish a subject who had killed his sovereign.

Background

King Mokjong (r. 997–1009) ascended the throne at the age of 18, and his mother, Queen Dowager Cheonchu (Queen Heonae), served as regent. The Queen Dowager was close to her relative Kim Chi-yang and placed great trust in him. When a son was born to the two of them, she tried to place that son on the throne. Since King Mokjong had no son, Grand Prince Wang Sun, the only surviving royal descendant among the grandsons of King Taejo, was the leading candidate for succession. It is recorded that the Queen Dowager had Grand Prince Daeryang made into a monk, expelled him to Sunggyo Temple and Sinhyeol Temple, and attempted to kill him several times.

Course of Events

King Mokjong's Illness

On the day Imsin (16th day) of the first lunar month of 1009, a fire broke out in the storehouse of the Daebu office and spread to Cheonchu Hall. Seeing the halls and storehouses reduced to ashes, King Mokjong grieved and fell ill. In secret, he discussed the succession with Chae Chung-sun, Choi Hang, and others, and sent Hwangbo Yu-ui to bring Grand Prince Daeryang from Sinhyeol Temple. Fearing a rebellion by the faction of Kim Chi-yang, he also summoned Gang Jo, Commissioner of Military Affairs stationed in Seogyeong, to come to Gaegyeong and provide protection.

Gang Jo Raises Troops

According to the Encyclopedia of Korean Culture, Gang Jo, while on his way to Gaegyeong, heard a false rumor that the king had already died and returned to his headquarters. He then set out again for Gaegyeong at the head of 5,000 soldiers. On reaching Pyeongju, he learned that the king was still alive and hesitated, but judged that as long as King Mokjong lived, Queen Dowager Cheonchu and the faction of Kim Chi-yang could not be removed. He therefore resolved to depose the king and sent Kim Eung-in to Sinhyeol Temple to bring Grand Prince Daeryang. The Goryeosa records that "Gang Jo, Commissioner of Military Affairs of Seogyeong, led his armored soldiers and came, and at last plotted to depose the king and install another."

Deposition and Killing

On the day Musin (2nd day) of the second lunar month, King Mokjong asked to withdraw to Yonghueung Temple and Gwibeop Temple to take refuge. On the day Gichuk (3rd day), Gang Jo's soldiers broke into the palace gate. Knowing that he could not escape harm, King Mokjong went out to Beopwang Temple weeping together with the Queen Dowager. Soon Hwangbo Yu-ui and others escorted Grand Prince Daeryang to the palace, and he ascended the throne; this was King Hyeonjong. Gang Jo demoted King Mokjong to Duke Yangguk, executed Kim Chi-yang, his son, Yu Haeng-gan, and four others, a total of seven people, and exiled their followers and some thirty relatives of Queen Dowager Cheonchu to islands.