The military of Goryeo was the primary military force of the Goryeo dynasty. During the Later Three Kingdoms period, Wang Kŏn overthrew the Taebong ruler, Kung Ye, and renamed it Goryeo after the Goguryeo dynasty. He led the kingdom's armies and navies against Silla and Later Baekje and unified the peninsula. Goryeo was able to mobilize sizable military might during times of war.
In the early period, the army was known for successfully defending the northern borders from the Khitans and the Jurchens. But the Imperial Court and the official scholars mistreated the military and overthrew the emperor, establishing a military regime that lasted a century. In the middle period, the army was also known for repelling the Mongol Empire until they capitulated after the ninth invasion, reducing the emperor to the status of king. The military regime opposed Mongol rule until the royal court overthrew them under their direction. The Sambyeolcho Army revolted against the Mongols in response until they suppressed them.
The navy was known for aiding the Mongols in invading Japan, but the Japanese defeated them, leaving the south defenseless against Wokou Pirate raids. The navy innovated gunpowder weaponry after the Mongol's use in the invasion of Japan to retrofit their ships with cannons and rockets to strengthen their naval defenses.
During the late period, King Gongmin purged Goryeo of Mongol influence and regained their sovereignty. They invaded the north, retaking some of Goguryeo's territories south of Manchuria. However, they lost them during the Red Turban Invasion of Goryeo but repelled them. However, the wars brought Goryeo to ruin. General Yi Sŏng-gye, who was ordered to attack the Ming to regain Liaodong retreated from Wihwado and overthrew the Goryeo and established the Joseon dynasty.
History Later Three Kingdoms period and the War for Unification From 889 to 935 AD, the Unified Shilla began to decline from corruption and internal strife, which led to the revival of Later Baekje and Later Goguryeo. A monk named Kung Ye founded Hugoguryeo but changed the names to Majin and Taebong in later years. Taejo's father, Wang Yung (later posthumously given the temple name of Sejo of Goryeo), along with many local clans, quickly surrendered to Kung Ye. Wang Kŏn followed his father into service under Kung Ye, the future leader of Taebong, and he began his service under Kung Ye's command. Kung Ye at Encyclopedia of Korean Culture Kung Ye at Doosan Encyclopedia
In 900, he led a successful campaign against local clans and the army of Later Baekje in the Chungju area, gaining more fame and recognition from the king. In 903, he led a famous naval campaign against the southwestern coastline of Later Baekje (Keumsung, later Naju) while Kyŏn Hwŏn was at war against Silla. He led several more military campaigns and helped conquered people living in poverty under Silla's rule. The public favored him due to his leadership and generosity. He also led Taebong's Navy, took Geumseong from the Later Baekje, renamed it Naju, and stationed the troops in 903. In 909, Wang Kon became Admiral of the Navy and led the naval forces. Kyŏn Hwŏn captured the envoy's ship from Yeomhae County within the jurisdiction of Gwangju. That year, Wang Kon captured Jindo and Koido (皐夷島) of the Later Baekje with 2,500 soldiers. The following year, when Kyŏn Hwŏn threatened Naju again, Wang Kŏn defeated Kyŏn Hwŏn's naval forces at the Naju port, and arrived at the port of Bannamhyeon (潘南縣), captured the pirate leader Neungchang, and sent it to Gungye to behead him. This would be Wang Kon's naval military activity before the founding of Goryeo and, at the same time, Taebong's maritime activity.
However, Kung Ye began to refer to himself as the Buddha and persecuted people who expressed their opposition to his religious arguments. He executed many monks, then later, even his wife and two sons, and the public began to turn away from him. His costly rituals and harsh rule caused even more opposition. In 918, four of his generals—Hong Yu, Pae Hyŏn-gyŏng, Sin Sung-gyŏm and Pok Chigyŏm—overthrew Taebong and installed Wang Kon as King Taejo.궁예, 디지털한국학
In 927, Kyŏn Hwŏn of Later Baekje led forces into Silla's capital, Gyeongju, capturing and executing its king, King Gyeongae. Then he established King Gyeongsun as his puppet monarch before he turned his army toward Goryeo. Hearing of the news, Taejo planned a strike with 5,000 cavalrymen to attack Kyŏn's troops on the way back home at Gongsan near Daegu.Il-yeon: Samguk Yusa: Legends and History of the Three Kingdoms of Ancient Korea, translated by Tae-Hung Ha and Grafton K. Mintz. Book Two, page 128. Silk Pagoda (2006). He met Later Baekje forces and suffered a disastrous defeat, losing most of his army, including his generals Kim Nak and Sin Sung-gyŏm, the very same man who crowned Wang as a king. However, Goryeo quickly recovered from defeat and successfully defended Later Baekje's attack on its front.
In 935, the last king of Silla, King Gyeongsun, felt there was no way to revive his kingdom and surrendered his entire land to Taejo. Taejo gladly accepted his surrender and gave him the title of prince, and accepted his daughter as one of his wives (Wang had six queens and many more wives as he married daughters of every single local leader). It caused much disgust to Kyŏn Hwŏn. Kyŏn's father, who held his claim to the Sangju region, also defected and surrendered to Goryeo and was received as the father of a king. Kyŏn Hwŏn's oldest son, Kyŏn Sin-gŏm, led a coup with his brothers Yang-gŏm and Yong-gŏm, against their father, who favored their half-brother, Kŭm-gang, as his successor to the throne. Kyŏn Hwŏn was sent into exile and imprisoned in Geumsansa but escaped to Goryeo and was treated like Taejo's father, who died just before his surrender.
In 936, Wang led his final campaign against Kyŏn Sin-gŏm of Later Baekje. Kyŏn Sin-gŏm fought against Taejo, but facing many disadvantages and inner conflict, he surrendered to Taejo. Wang finally occupied Later Baekje formally and unified the nation for the second time since Unified Silla; he ruled until 943.
Goryeo–Khitan War Taejo displayed intense animosity toward the Khitans who had destroyed Balhae. The Liao dynasty sent 30 envoys with 50 camels as a gift in 942, but Wang Kŏn exiled the envoys and starved the camels under a bridge in retribution for Balhae, despite the major diplomatic repercussions. Taejo proposed to Gaozu of Later Jìn that they attack the Khitans as revenge for the destruction of Balhae, according to the Zizhi Tongjian. Furthermore, in his Ten Injunctions to his descendants, he stated that the Khitans are no different from beasts and should be guarded against.
The "Manbu Bridge Incident" of 942 forced Goryeo to prepare itself for a conflict with the Khitan Empire: Jeongjong established a military reserve force of 300,000 soldiers called the "Resplendent Army" in 947, and Gwangjong built fortresses north of the Chongchon River, expanding toward the Yalu River. The Khitans considered Goryeo a potential threat and, with tensions rising, invaded in 993. The Koreans were defeated in their first encounter with the Khitans, but successfully defended against them at the Chongchon River. Negotiations began between the Goryeo commander, Sŏ Hŭi, and the Liao commander, Xiao Sunning. In conclusion, Goryeo entered a nominal tributary relationship with Liao, severing relations with Song, and Liao conceded the land east of the Yalu River to Goryeo. Afterward, Goryeo established the "Six Garrison Settlements East of the River" in its new territory. In 994, Goryeo proposed to Song a joint military attack on Liao, but was declined; previously, in 985, when Song had proposed a joint military attack on Liao, Goryeo had declined. For a time, Goryeo and Liao enjoyed an amicable relationship. In 996, Seongjong married a Liao princess.
As the Khitan Empire expanded and became more powerful, it demanded that Goryeo cede the Six Garrison Settlements, but Goryeo refused. In 1009, Kang Cho staged a coup d'état, assassinating Mokjong and installing Hyeonjong on the throne. In the following year, under the pretext of avenging Mokjong, Emperor Shengzong of Liao led an invasion of Goryeo with an army of 400,000 soldiers. Meanwhile, Goryeo tried to establish relations with Song but was ignored, as Song had agreed to the Chanyuan Treaty in 1005. Goryeo won the first battle against Liao, led by Yang Kyu, but lost the second battle, led by Kang Cho: the Goryeo army suffered heavy casualties and was dispersed, and many commanders were captured or killed, including Kang Cho himself. Later, Pyongyang was successfully defended, but the Liao army marched toward Kaesong. Hyeonjong, upon the advice of Kang Kam-ch'an, evacuated south to Naju, and shortly afterward Kaesong was attacked and sacked by the Liao army. He then sent Ha Kong-jin and Go Yeong-gi to sue for peace, with a promise that he would pay homage in person to the Liao emperor, and the Khitans, who were sustaining attacks by the regrouped Korean army and disrupted supply lines, accepted and began their withdrawal. However, the Khitans were ceaselessly attacked during their withdrawal; Yang Kyu rescued 30,000 prisoners of war, but died in battle. According to the History of Liao, the Khitans were beset by heavy rains and discarded much of their armor and weapons. According to the Goryeosa, the Khitans were attacked while crossing the Yalu River and many drowned. Afterward, Hyeonjong did not fulfill his promise to pay homage in person to the Liao emperor, and when demanded to cede the Six Garrison Settlements, he refused.
The Khitans built a bridge across the Yalu River in 1014 and attacked in 1015, 1016, and 1017: victory went to the Koreans in 1015, the Khitans in 1016, and the Koreans in 1017. In 1018, Liao launched an invasion led by Xiao Paiya, the older brother of Xiao Sunning, with an army of 100,000 soldiers. The Liao army was immediately ambushed and suffered heavy casualties: the Goryeo commander Kang Kam-ch'an had dammed a large tributary of the Yalu River and released the water on the unsuspecting Khitan soldiers, who were then charged by 12,000 elite cavalry. The Liao army pushed on toward Kaesong under constant enemy harassment, but shortly turned around and retreated after failing to take the well-defended capital. The retreating Liao army was intercepted by Kang Kam-ch'an in modern-day Kusong and suffered a major defeat, with only a few thousand soldiers escaping. Shengzong intended to invade again but faced internal opposition. In 1020, Goryeo sent tribute and Liao accepted, thus resuming nominal tributary relations. Shengzong did not demand that Hyeonjong pay homage in person or cede the Six Garrison Settlements. The only terms were a "declaration of vassalage" and the release of a detained Liao envoy. The History of Liao claims that Hyeonjong "surrendered" and Shengzong "pardoned" him, but according to Hans Bielenstein, "[s]horn of its dynastic language, this means no more than that the two states concluded peace as equal partners (formalized in 1022)". Hyeonjong kept his reign title and maintained diplomatic relations with the Song dynasty. Kaesong was rebuilt, grander than before, and, from 1033 to 1044, the Cheolli Jangseong, a wall stretching from the mouth of the Yalu River to the east coast of the Korean Peninsula, was built for defense against future invasions. Liao never invaded Goryeo again.
Goryeo-Jurchen War