Overview
The unification of the Later Three Kingdoms was the event in 936 (19th year of Taejo of Goryeo) in which Goryeo defeated the army of Shin Geom of Later Baekje at the Battle of Illiecheon in Ilseon County (present-day Gumi, North Gyeongsang Province), and then received Shin Geom's surrender at Hwangsan (present-day Yeonsan, Nonsan, South Chungcheong Province), merging the Later Three Kingdoms into one. According to the Goryeosa, on the eighth day of the ninth lunar month (gapo day, corresponding to 26 September in the solar calendar) the two armies encamped on either side of the Illiecheon, and the Goryeo army, totaling 87,500 men including 40,000 cavalry, 23,000 infantry and 9,500 auxiliary cavalry, was the largest of the Later Three Kingdoms period. With this, the division of the Later Three Kingdoms, which had lasted since around 900, came to an end.
Background
Internal strife in Later Baekje
After suffering successive defeats at the Battle of Gochang in 930 and the Battle of Unju in 934, Later Baekje lost the initiative. In the third lunar month of 935, Shin Geom, the eldest son of Gyeonhwon, conspired with the minister Neunghwan and his younger brothers Yanggeom and Yonggeom to confine his father in Geumsansa Temple in Gimje, and then killed Geumgang, the fourth son whom Gyeonhwon had favored and intended to make his successor, and ascended the throne. Gyeonhwon escaped from Geumsansa in the sixth month, fled to Naju, and then surrendered to Goryeo; Taejo elevated him to Sangbo and had him reside in the Namgung. At the end of the same year, with the surrender of King Gyeongsun of Silla, Goryeo was left to face only Later Baekje.
Mobilization
In the second month of 936, Park Yeong-gyu, a general and son-in-law of Gyeonhwon, informed Goryeo that he would act in support of it. In the sixth month, Gyeonhwon requested an expedition, saying, "This old minister crossed the distant sea and submitted to the holy civilization in order to borrow your majesty's authority and cut down the rebellious son." Taejo at first intended to wait for the right time, but accepted his entreaty, and first sent Crown Prince Wang Mu (later King Hyejong) and General Park Sul-hui to Cheonan-bu with 10,000 infantry and cavalry. Cheonan-bu was a stronghold blocking the route of the Later Baekje army advancing northward. In the ninth month, Taejo led three armies, joined up with them at Cheonan-bu, and advanced toward Ilseon County, while Shin Geom also led his troops to meet them.
Course of the Campaign
Organization of the Goryeo army
The entry for the ninth month of the 19th year of Taejo in the Goryeosa describes the organization of the Goryeo army in detail.
- Left column: Gyeonhwon, along with Grand Minister Gyeon Gwon, Park Sul-hui, Hwangbo Geumsan, and Wonyun Kang Yu-yeong, led 10,000 cavalry; Grand General Neung-dal, Gi-eon, Han Sun-myeong, and Heun-ak led 10,000 infantry.
- Right column: Grand Minister Kim Cheol, Hong Yu, and Park Su-gyeong, Wonbo Yeon-ju, and Wonyun Hwallyang led 10,000 cavalry; Grand General Samsun and Junryang led 10,000 infantry.
- Central army: Myeongju Daegwang Wang Sun-sik, Grand Minister Geung-jun, Wang Ryeom, and Wang Ye led 20,000 cavalry; Grand Minister Yu Geum-pil and others led 9,500 nimble cavalry of the northern peoples such as Heuksu, Dalgo, and Cheolleuk; and the Ucheon, Cheonmu, and Gancheon troops each led 1,000 infantry.
- Reinforcements: Grand General Gong Hwon and others led 300 cavalry and 14,700 troops from various fortresses.
The Encyclopedia of Korean Culture notes that more than 38 generals are named in the Goryeosa, and holds that mobilization on this scale went beyond the "punishment of the rebellious son" that Gyeonhwon had requested, aiming at the destruction of Later Baekje itself.
The decisive battle at Illiecheon
On the eighth day of the ninth month the two armies encamped on either side of the Illiecheon, and Taejo examined the strength of the forces together with Gyeonhwon. When the Goryeo army advanced beating drums, the Goryeosa records that white clouds shaped like swords and spears rose above the Goryeo army and moved toward the enemy camp. Seeing how enormous the Goryeo forces were, four Later Baekje left-column generals, Hyobong, Deoksul, Aesul, and Myeonggil, removed their helmets, threw down their spears, came before Gyeonhwon's horse and surrendered, and the Later Baekje army was so disheartened that it dared not move. When Taejo asked where Shin Geom was, Hyobong and the others replied, "He is in the central army; if we attack from left and right together, we will surely break through."
Taejo ordered Grand General Gong Hwon to attack the Later Baekje central army directly, and when the three armies advanced simultaneously and attacked, the Later Baekje army collapsed completely. The Goryeo army captured 3,200 men, including generals Heun-gang, Gyeondal, Eunsul, Geumsik, and Woobong, and beheaded more than 5,700. The Goryeosa records that the Later Baekje soldiers turned their spears upside down and attacked one another, showing that the formation collapsed through internal strife.
Surrender at Hwangsan
The Goryeo army pursued the enemy as far as Hwangsan-gun, crossed the Tan Pass, and encamped at Maseong. The Encyclopedia of Korean Culture holds that Shin Geom had tried to regroup at Nonsan after moving from Gimcheon over Chupungnyeong through Yeongdong and Geumsan. However, realizing that he could hold out no longer, Shin Geom surrendered, leading his younger brother Yanggeom, the governor of Cheongju (Ching-ju), his other younger brother Yonggeom, the governor of Gwangju, and civil and military officials. The Tan Pass is identified with several places, including the Un-ju Myeon of Wanju, the Mado Pass east of Daejeon, and the Sutgogae of Jinsan Myeon in Geumsan.
Results
- Taejo sent 3,200 captured Later Baekje soldiers back to their homes, and sent only about 40 men, including Heun-gang, Bu-dal, Woo-bong, and Gyeon-dal, together with their wives and children, to Gaegyeong.
- Neunghwan, who had confined his father and set up Shin Geom, was executed; Yanggeom and Yonggeom were exiled to Jinju and then soon killed. Shin Geom had ascended the throne under threat from others and had surrendered of his own accord, so he escaped death and received an official post. However, the Encyclopedia of Korean Culture estimates that he was also soon killed, since there is no record about Shin Geom at all afterward.
- Gyeonhwon died after several days in a temple at Hwangsan, having developed a back carbuncle from worry and resentment.
- Taejo entered the Later Baekje capital and ordered, "The leader has already surrendered; do not harm my people," comforted the soldiers, and recruited talented people. The Goryeosa records that military discipline was strict and not the slightest offense was committed, so the towns were peaceful and the elderly and children all shouted "long live" (manse).
- In the same month, Taejo returned to Gaegyeong, received the congratulations of officials and the people at Wibong-ru, and composed and promulgated the Jeonggye in one volume and the Gyebaekryeoseo in eight sections.
- In the same year, Taejo built Gaetaesa Temple in Yeonsan, within the Hwangsan area, to commemorate the unification.
Impact and Significance
The unification of 936 made Goryeo a single dynasty encompassing Silla and Later Baekje, and by also accepting the people of Balhae who had come over after the fall of Balhae in 926, it laid the groundwork for national integration. The significance of the unification is often noted in two points: unlike the unification of the Three Kingdoms by Silla, which relied on the power of a foreign power (Tang), Goryeo's unification was achieved through the integration of internal forces, and it formed a new ruling class by embracing the Silla aristocracy and local powerful families (hoho) across the country.
References