In the geographic monographs of the Book of Han, the word Goguryeo (hanja: 高句驪) made its first appearance in 113 BCE in the name of Gaogouli County under the jurisdiction of Xuantu Commandery. In the Old Book of Tang (945), it is recorded that Emperor Taizong refers to Goguryeo's history as being some 900 years old. According to the 12th-century Samguk sagi and the 13th-century Samgungnyusa, a prince from the Buyeo kingdom named Jumong fled after a power struggle with other princes of the court and founded Goguryeo in 37 BCE in a region called Jolbon Buyeo, usually thought to be located in the middle Yalu and Tongjia River basin, overlapping the current China-North Korea border.
In 75 BCE, a group of Yemaek who may have originated from Goguryeo made an incursion into China's Xuantu Commandery west of the Yalu.
However, the weight of textual evidence from the Old Book of Tang, New Book of Tang, the Samguk sagi, the Nihon Shoki as well as other ancient sources would support a 37 BCE or "middle" first century BCE foundation date for Goguryeo. Archaeological evidence would support centralized groups of Yemaek tribes in the 2nd century BC, but there is no direct evidence that would suggest these Yemaek groups were known as or would identify themselves as Goguryeo. The first mention of Goguryeo as a group label associated with Yemaek tribes is a reference in the Han Shu that discusses a Goguryeo revolt in 12 CE, during which they broke away from the influence of the Chinese at Xuantu.
At its founding, the Goguryeo people are believed to be a blend of people from Buyeo and Yemaek, as leadership from Buyeo may have fled their kingdom and integrated with existing Yemaek chiefdoms. The Records of the Three Kingdoms, in the section titled "Accounts of the Eastern Barbarians", implied that Buyeo and the Yemaek people were ethnically related and spoke a similar language.
Goguryeo and Baekje shared founding myths and originated from Buyeo.
Jumong and the foundation myth
Image of the mythical figure from the Goguryeo-era Ohoe Tomb 4.
The earliest mention of Jumong is in the 4th-century Gwanggaeto Stele. Jumong is the modern Korean transcription of the hanja 朱蒙 Jumong, 鄒牟 Chumo, or 仲牟 Jungmo.
The Stele states that Jumong was the first king and ancestor of Goguryeo and that he was the son of the prince of Buyeo and daughter of Habaek (Hangul: 하백; Hanja: 河伯), the god of the Amnok River or, according to an alternate interpretation, the sun god Haebak (Hangul: 해밝). The Samguk sagi and Samgungnyusa paint additional detail and names Jumong's mother as Yuhwa (Hangul: 유화; Hanja: 柳花). Jumong's biological father was said to be a man named Haemosu (Hangul: 해모수; Hanja: 解慕漱) who is described as a "strong man" and "a heavenly prince." The river god chased Yuhwa away to the Ubal River (Hangul: 우발수; Hanja: 優渤水) due to her pregnancy, where she met and became the concubine of Geumwa.
Jumong was well known for his exceptional archery skills. Eventually, Geumwa's sons became jealous of him, and Jumong was forced to leave Eastern Buyeo. The Stele and later Korean sources disagree as to which Buyeo Jumong came from. The Stele says he came from Buyeo and the Samgungnyusa and Samguk sagi say he came from Eastern Buyeo. Jumong eventually made it to Jolbon, where he married Soseono, daughter of its ruler. He subsequently became king himself, founding Goguryeo with a small group of his followers from his native country.
A traditional account from the "Annals of Baekje" section in the Samguk sagi says that Soseono was the daughter of Yeon Tabal, a wealthy influential figure in Jolbon and married to Jumong. However, the same source officially states that the king of Jolbon gave his daughter to Jumong, who had escaped with his followers from Eastern Buyeo, in marriage. She gave her husband, Jumong, financial support in founding the new statelet, Goguryeo. After Yuri, son of Jumong and his first wife, Lady Ye, came from Dongbuyeo and succeeded Jumong, she left Goguryeo, taking her two sons Biryu and Onjo south to found their own kingdoms, one of which was Baekje.
Jumong's given surname was "Hae" (Hangul: 해; Hanja: 解), the name of the Buyeo rulers. According to the Samgungnyusa, Jumong changed his surname to "Go" (Hangul: 고; Hanja: 高) in conscious reflection of his divine parentage. Jumong is recorded to have conquered the tribal states of Biryu (Hangul: 비류국; Hanja: 沸流國) in 36 BCE, Haeng-in (Hangul: 행인국; Hanja: 荇人國) in 33 BCE, and Northern Okjeo in 28 BCE.
Centralization and early expansion (mid-first century)
Goguryeo developed from a league of various Yemaek tribes to an early state and rapidly expanded its power from their original basin of control in the Hun River drainage. In the time of Taejodae in 53 CE, five local tribes were reorganized into five centrally ruled districts. Foreign relations and the military were controlled by the king. Early expansion might be best explained by ecology; Goguryeo controlled territory in what is currently central and southern Manchuria and northern Korea, which are both very mountainous and lacking in arable land. Upon centralizing, Goguryeo might have been unable to harness enough resources from the region to feed its population and thus, following historical pastoralist tendencies, would have sought to raid and exploit neighboring societies for their land and resources. Aggressive military activities may have also aided expansion, allowing Goguryeo to exact tribute from their tribal neighbors and dominate them politically and economically.
Taejo conquered the Okjeo tribes of what is now northeastern Korea as well as the Dongye and other tribes in Southeastern Manchuria and Northern Korea. From the increase of resources and manpower that these subjugated tribes gave him, Taejodae led Goguryeo in attacking the Han Commanderies of Lelang and Xuantu in the Korean and Liaodong Peninsulas, becoming fully independent from them.
Generally, Taejodae allowed the conquered tribes to retain their chieftains, but required them to report to governors who were related to Goguryeo's royal line; tribes under Goguryeo's jurisdiction were expected to provide heavy tribute. Taejodae and his successors channeled these increased resources to continuing Goguryeo's expansion to the north and west. New laws regulated peasants and the aristocracy, as tribal leaders continued to be absorbed into the central aristocracy. Royal succession changed from fraternal to patrilineal, stabilizing the royal court.
The expanding Goguryeo kingdom soon entered into direct military contact with the Liaodong commandery to its west. Pressure from Liaodong forced Goguryeo to move their capital in the Hun River valley to the Yalu River valley near Hwando.
In the chaos following the fall of the Han Dynasty, the former Han commanderies had broken free of control and were ruled by various independent warlords. Surrounded by these commanderies, who were governed by aggressive warlords, Goguryeo moved to improve relations with the newly created dynasty of Cao Wei in China and sent tribute in 220. In 238, Goguryeo entered into a formal alliance with Wei to destroy the Liaodong commandery.
When Liaodong was finally conquered by Wei, cooperation between Wei and Goguryeo fell apart and Goguryeo attacked the western edges of Liaodong, which incited a Wei counterattack in 244. Thus, Goguryeo initiated the Goguryeo–Wei War in 242, trying to cut off Chinese access to its territories in Korea by attempting to take a Chinese fort. However, the Wei state responded by invading and defeated Goguryeo. The capital at Hwando was destroyed by Wei forces in 244. It is said that Dongcheon, with his army destroyed, fled for a while to the Okjeo state in the east. Wei invaded again in 259 but was defeated at Yangmaenggok; according to the Samguk sagi, Jungcheon assembled 5,000 elite cavalry and defeated the invading Wei troops, beheading 8,000 enemies.
Revival and further expansion (300 to 390)
A gilt-bronze crown from Goguryeo believed to have once adorned the head of a bodhisattva
In only 70 years, Goguryeo rebuilt its capital Hwando and again began to raid the Liaodong, Lelang and Xuantu commandaries. As Goguryeo extended its reach into the Liaodong Peninsula, the last Chinese commandery at Lelang was conquered and absorbed by Micheon in 313, bringing the remaining northern part of the Korean peninsula into the fold. This conquest resulted in the end of Chinese rule over territory in the northern Korean peninsula, which had spanned 400 years. From that point on, until the 7th century, territorial control of the peninsula would be contested primarily by the Three Kingdoms of Korea.
Goguryeo met major setbacks and defeats during the reign of Gogukwon in the 4th century. In the early 4th century, the nomadic proto-Mongol Xianbei people occupied northern China; during the winter of 342, the Xianbei of Former Yan, ruled by the Murong clan, attacked and destroyed Goguryeo's capital, Hwando, capturing 50,000 Goguryeo men and women to use as slave labor in addition to taking the Queen Dowager and Queen prisoner, and forced Gogukwon to flee for a while. The Xianbei also devastated Buyeo in 346, accelerating Buyeo migration to the Korean peninsula. In 371, Geunchogo of Baekje killed Gogukwon in the
Battle of Chiyang and sacked Pyongyang, one of Goguryeo's largest cities.
Sosurim, who succeeded the slain Gogukwon, reshaped the nation's institutions to save it from a great crisis. Turning to domestic stability and the unification of various conquered tribes, Sosurim proclaimed new laws, embraced Buddhism as the state religion in 372, and established a national educational institute called the Taehak (Hangul: 태학; Hanja: 太學). Due to the defeats that Goguryeo had suffered at the hands of the Xianbei and Baekje, Sosurim instituted military reforms aimed at preventing such defeats in the future. Sosurim's internal arrangements laid the groundwork for Gwanggaeto's expansion. His successor and the father of Gwanggaeto the Great, Gogukyang, invaded Later Yan, the successor state of Former Yan, in 385 and Baekje in 386.
Goguryeo used its military to protect and exploit semi-nomadic peoples, who served as vassals, foot soldiers, or slaves, such as the Okjeo people in the northeast end of the Korean peninsula, and the Mohe people in Manchuria, who would later become the Jurchens.
Zenith of Goguryeo's Power (391 to 531 AD)
A royal tomb, located in Ji'an, Jilin
, was built by the Goguryeo Kingdom.
Goguryeo experienced a golden age under Gwanggaeto the Great and his son Jangsu. During this period, Goguryeo territories included three fourths of the Korean Peninsula, including what is now Seoul, almost all of Manchuria, parts of Inner Mongolia, and parts of Russia. There is archaeological evidence that Goguryeo's maximum extent lay even further west in present-day Mongolia, based on discoveries of Goguryeo fortress ruins in Mongolia.
Gwanggaeto the Great (r. 391–412) was a highly energetic emperor who is remembered for his rapid military expansion of the realm. He instituted the era name of Yeongnak or Eternal Rejoicing, affirming that Goguryeo was on equal standing with the dynasties in the Chinese mainland. Gwanggaeto conquered 64 walled cities and 1,400 villages during his campaigns. To the west, he destroyed neighboring Khitan tribes and invaded Later Yan, conquering the entire Liaodong Peninsula; to the north and east, he annexed much of Buyeo and conquered the Sushen, who were Tungusic ancestors of the Jurchens and Manchus; and to the south, he defeated and subjugated Baekje, contributed to the dissolution of Gaya, and vassalized Silla after defending it from a coalition of Baekje, Gaya, and Wa. Gwanggaeto brought about a loose unification of the Korean Peninsula, and achieved undisputed control of most of Manchuria and over two thirds of the Korean Peninsula.
Gwanggaeto's exploits were recorded on a huge memorial stele erected by his son Jangsu, located in present-day Ji'an on the border between China and North Korea.
Jangsu (r. 413–491) ascended to the throne in 413 and moved the capital in 427 to Pyongyang, a more suitable region to grow into a burgeoning metropolitan capital, which led Goguryeo to achieve a high level of cultural and economic prosperity. Jangsu, like his father, continued Goguryeo's territorial expansion into Manchuria and reached the Songhua River to the north. He invaded the Khitans, and then attacked the Didouyu, located in eastern Mongolia, with his Rouran allies. Like his father, Jangsu also achieved a loose unification of the Three Kingdoms of Korea. He defeated Baekje and Silla and gained large amounts of territory from both. In addition, Jangsu's long reign saw the perfecting of Goguryeo's political, economic and other institutional arrangements. Jangsu ruled Goguryeo for 79 years until the age of 98, the longest reign in East Asian history.
During the reign of Munja, Goguryeo completely annexed Buyeo, signifying Goguryeo's furthest-ever expansion north, while continuing its strong influence over the kingdoms of Silla and Baekje, and the tribes of Wuji and Khitan.
Internal strife (531 to 551)
Goguryeo reached its zenith in the 6th century. After this, however, it began a steady decline. Anjang was assassinated, and succeeded by his brother Anwon, during whose reign aristocratic factionalism increased. A political schism deepened as two factions advocated different princes for succession, until the eight-year-old Yang-won was finally crowned. But the power struggle was never resolved definitively, as renegade magistrates with private armies appointed themselves de facto rulers of their areas of control.
Taking advantage of Goguryeo's internal struggle, a nomadic group called the Tuchueh attacked Goguryeo's northern castles in the 550s and conquered some of Goguryeo's northern lands. Weakening Goguryeo even more, as civil war continued among feudal lords over royal succession, Baekje and Silla allied to attack Goguryeo from the south in 551.
Conflicts of the late 6th and 7th centuries
In the late 6th and early 7th centuries, Goguryeo was often in military conflict with the Sui and Tang dynasties of China. Its relations with Baekje and Silla were complex and alternated between alliances and enmity. A neighbor in the northwest were the Eastern Göktürk which was a nominal ally of Goguryeo.
Goguryeo's loss of the Han River Valley
In 551 AD, Baekje and Silla entered into an alliance to attack Goguryeo and conquer the Han River valley, an important strategic area close to the center of the peninsula and a very rich agricultural region. After Baekje exhausted themselves with a series of costly assaults on Goguryeo fortifications, Silla troops, arriving on the pretense of offering assistance, attacked and took possession of the entire Han River valley in 553. Incensed by this betrayal, Seong launched a retaliatory strike against Silla's western border in the following year but was captured and killed.
The war, along the middle of the Korean peninsula, had very important consequences. It effectively made Baekje the weakest player on the Korean Peninsula and gave Silla an important resource and population rich area as a base for expansion. Conversely, it denied Goguryeo the use of the area, which weakened the kingdom. It also gave Silla direct access to the Yellow Sea, opening up direct trade and diplomatic access to the Chinese dynasties and accelerating Silla's adoption of Chinese culture. Thus, Silla could rely less on Goguryeo for elements of civilization and could get culture and technology directly from China. This increasing tilt of Silla to China would result in an alliance that would prove disastrous for Goguryeo in the late 7th century.
Goguryeo's expansion conflicted with Sui China and increased tensions. In 598, Goguryeo made a preemptive attack on Liaoxi, leading Emperor Wen to launch a counterattack by land and sea that ended in disaster for Sui.
Sui's most disastrous campaign against Goguryeo was in 612, in which Sui, according to the History of the Sui Dynasty, mobilized 30 Division armies, about 1,133,800 combat troops. Pinned along Goguryeo's line of fortifications on the Liao River, a detachment of nine division armies, about 305,000 troops, bypassed the main defensive lines and headed towards the Goguryeo capital of Pyongyang to link up with Sui naval forces, who had reinforcements and supplies.
However, Goguryeo was able to defeat the Sui navy, thus when the Sui's nine division armies finally reached Pyongyang, they didn't have the supplies for a lengthy siege. Sui troops retreated, but General Eulji Mundeok led the Goguryeo troops to victory by luring the Sui into an ambush outside of Pyongyang. At the Battle of Salsu, Goguryeo soldiers released water from a dam, which split the Sui army and cut off their escape route. Of the original 305,000 soldiers of Sui's nine division armies, it is said that only 2,700 escaped to Sui China.
The 613 and 614 campaigns were aborted after launch—the 613 campaign was terminated when the Sui general Yang Xuangan rebelled against Emperor Yang, while the 614 campaign was terminated after Goguryeo offered a truce and returned Husi Zheng (斛斯政), a defecting Sui general who had fled to Goguryeo, Emperor Yang later had Husi executed. Emperor Yang planned another attack on Goguryeo in 615, but due to Sui's deteroriating internal state he was never able to launch it. Sui was weakened due to rebellions against Emperor Yang's rule and his failed attempts to conquer Goguryeo. They could not attack further because the provinces in the Sui heartland would not send logistical support.
Emperor Yang's disastrous defeats in Korea greatly contributed to the collapse of the Sui dynasty.
Goguryeo–Tang War and the Silla–Tang alliance
First campaign in the Goguryeo–Tang War.
In the winter of 642, King Yeongnyu was apprehensive about Yeon Gaesomun, one of the great nobles of Goguryeo, and plotted with other officials to kill him. However, Yeon Gaesomun caught news of the plot and killed Yeongnyu and 100 officials, initiating a coup d'état. He proceeded to enthrone Yeongnyu's nephew, Go Jang, as King Bojang while wielding de facto control of Goguryeo himself as the generalissimo ((in Korean)). Yeon Gaesomun took an increasingly provocative stance against Silla and Tang China. In 643, under pressure from the Goguryeo–Baekje alliance, Silla requested military aid from Tang. In 644, Tang began preparations for a major campaign against Goguryeo.
In 645, Emperor Taizong, who had a personal ambition to defeat Goguryeo and was determined to succeed where Emperor Yang had failed, personally led an attack on Goguryeo. The Tang army captured a number of Goguryeo fortresses, including the important Yodong/Liaodong Fortress (遼東城, in modern Liaoyang, Liaoning), and defeated large Goguryeo armies in its path. Ansi City (in modern Haicheng, Liaoning) was the last fortress that would clear the Liaodong Peninsula of significant defensive works and was promptly put under siege. However, the capable defense put up by Ansi's commanding general (whose name is controversial but traditionally is believed to be Yang Manchun) stymied Tang forces and, in late fall, with winter fast approaching and his supplies running low, Emperor Taizong withdrew. The campaign was unsuccessful for the Tang Chinese, failing to capture Ansi Fortress after a protracted siege that lasted more than 60 days. Emperor Taizong invaded Goguryeo again in 647 and 648, but was defeated both times.
Emperor Taizong prepared another invasion in 649, but died in the summer, possibly due to an illness he contracted during his Korean campaigns. His son Emperor Gaozong continued his campaigns. Upon the suggestion of Kim Chunchu, the Silla–Tang alliance first conquered Baekje in 660 to break up the Goguryeo–Baekje alliance, and then turned its full attention to Goguryeo. However, Emperor Gaozong, too, was unable to defeat Goguryeo led by Yeon Gaesomun; one of Yeon Gaesomun's most notable victories came in 662 at the Battle of Sasu (蛇水), where he annihilated the Tang forces and killed the invading general
Pang Xiaotai (龐孝泰) and all 13 of his sons. Therefore, while Yeon Gaesomun was alive, Tang could not defeat Goguryeo.
In the summer of 666, Yeon Gaesomun died of a natural cause and Goguryeo was thrown into chaos and weakened by a succession struggle among his sons and younger brother. He was initially succeeded as Dae Mangniji, the highest position newly made under the ruling period of Yeon Gaesomun, by his oldest son Yeon Namsaeng. As Yeon Namsaeng subsequently carried out a tour of Goguryeo territory, however, rumors began to spread both that Yeon Namsaeng was going to kill his younger brothers Yeon Namgeon and Yeon Namsan, whom he had left in charge at Pyongyang, and that Yeon Namgeon and Yeon Namsan were planning to rebel against Yeon Namsaeng. When Yeon Namsaeng subsequently sent officials close to him back to Pyongyang to try to spy on the situation, Yeon Namgeon arrested them and declared himself Dae Mangniji, attacking his brother. Yeon Namsaeng sent his son
Cheon Heonseong (泉獻誠), as Yeon Namsaeng changed his family name from Yeon (淵) to Cheon (泉) observe naming taboo for Emperor Gaozu, to Tang to seek aid. Emperor Gaozong saw this as an opportunity and sent an army to attack and destroy Goguryeo. In the middle of Goguryeo's power struggles between Yeon Gaesomun's successors, his younger brother, Yeon Jeongto, defected to the Silla side.
In 667, the Chinese army crossed the Liao River and captured Shin/Xin Fortress (新城, in modern Fushun, Liaoning). The Tang forces thereafter fought off counterattacks by Yeon Namgeon, and joined forces with and received every possible assistance from the defector Yeon Namsaeng, although they were initially unable to cross the Yalu River due to resistance. In spring of 668, Li Ji turned his attention to Goguryeo's northern cities, capturing the important city of Buyeo (扶餘, in modern Nong'an, Jilin). In fall of 668, he crossed the Yalu River and put Pyongyang under siege in concert with the Silla army.
Yeon Namsan and Bojang surrendered, and while Yeon Namgeon continued to resist in the inner city, his general, the Buddhist monk
Shin Seong (信誠) turned against him and surrendered the inner city to Tang forces. Yeon Namgeon tried to commit suicide, but was seized and treated. This was the end of Goguryeo, and Tang annexed Goguryeo into its territory, with Xue Rengui being put initially in charge of former Goguryeo territory as protector general. The violent dissension resulting from Yeon Gaesomun's death proved to be the primary reason for the Tang–Silla triumph, thanks to the division, defections, and widespread demoralization it caused. The alliance with Silla had also proved to be invaluable, thanks to the ability to attack Goguryeo from opposite directions, and both military and logistical aid from Silla.
However, there was much resistance to Tang rule (fanned by Silla, which was displeased that Tang did not give it Goguryeo or Baekje's territory), and in 669, following Emperor Gaozong's order, a part of the Goguryeo people were forced to move to the region between the Yangtze River and the Huai River, as well as the regions south of the Qinling Mountains and west of Chang'an, only leaving old and weak inhabitants in the original land. Some people entered the service of the Tang government, such as Go Sagye and his son Gao Xianzhi (Go Seonji in Korean), the famed general who commanded the Tang forces at the Battle of Talas.
Silla thus unified most of the Korean peninsula in 668, but the kingdom's reliance on China's Tang Dynasty had its price. Tang set up the Protectorate General to Pacify the East, governed by Xue Rengui, but faced increasing problems ruling the former inhabitants of Goguryeo, as well as Silla's resistance to Tang's remaining presence on the Korean Peninsula. Silla had to forcibly resist the imposition of Chinese rule over the entire peninsula, which lead to the Silla–Tang Wars, but their own strength did not extend beyond the Taedong River.
After the fall of Goguryeo in 668, many Goguryeo people rebelled against the Tang and Silla by starting Goguryeo revival movements. Among these were Geom Mojam, Dae Jung-sang, and several famous generals. The Tang Dynasty tried but failed to establish several commanderies to rule over the area.
In 677, Tang crowned Bojang as the "King of Joseon" and put him in charge of the Liaodong commandery of the Protectorate General to Pacify the East. However, Bojang continued to foment rebellions against Tang in an attempt to revive Goguryeo, organizing Goguryeo refugees and allying with the Mohe tribes. He was eventually exiled to Sichuan in 681, and died the following year.
The Protectorate General to Pacify the East was installed by the Tang government to rule and keep control over the former territories of the fallen Goguryeo. It was first put under the control of Tang General Xue Rengui, but was later replaced by Bojang due the negative responses of the Goguryeo people. Bojang was sent into exile for assisting Goguryeo revival movements, but was succeeded by his descendants. Bojang's descendants declared independence from Tang during the same period as the An Lushan Rebellion and Li Zhengji (Yi Jeong-gi in Korean)'s rebellion in Shandong. The Protectorate General to Pacify the East was renamed "Little Goguryeo" until its eventual absorption into Balhae under the reign of Seon.
Geom Mojam and Anseung rose briefly at the Han Fortress (한성, 漢城, in modern Chaeryong, South Hwanghae), but failed, when Anseung surrendered to Silla. Go Anseung ordered the assassination of Geom Mojam, and defected to Silla, where he was given a small amount of land to rule over. There, Anseung established the
State of Bodeok (보덕, 報德), incited a rebellion, which was promptly crushed by Sinmun. Anseung was then forced to reside in the Silla capital, given a Silla bride and had to adopt the Silla Royal surname of "Kim."
Dae Jung-sang and his son Dae Jo-yeong, both former Goguryeo generals, regained most of Goguryeo's northern land after its downfall in 668, established the Kingdom of Jin (진, 震), which was renamed to Balhae after 713. To the south of Balhae, Silla controlled the Korean peninsula south of the Taedong River, and Manchuria (present-day northeastern China) was conquered by Balhae. Balhae considered itself (particularly in diplomatic correspondence with Japan) a successor state of Goguryeo.
In 901, the general Gung Ye rebelled against Later Silla and founded Later Goguryeo (renamed to Taebong in 911), which considered itself to be a successor of Goguryeo. Later Goguryeo originated in the northern regions, including Songak (modern Kaesong), which were the strongholds of Goguryeo refugees. Later Goguryeo's original capital was established in Songak, the hometown of Wang Geon, a prominent general under Gung Ye. Wang Geon was a descendant of Goguryeo and traced his ancestry to a noble Goguryeo clan. In 918, Wang Geon overthrew Gung Ye and established Goryeo, as the successor of Goguryeo, and laid claim to Manchuria as Goryeo's rightful legacy. Wang Geon unified the Later Three Kingdoms in 936, and Goryeo ruled the Korean Peninsula until 1392.
In the 10th century, Balhae collapsed and much of its ruling class and the last crown prince Dae Gwang-hyeon fled to Goryeo. The Balhae refugees were warmly welcomed and included in the ruling family by Wang Geon, who felt a strong familial kinship with Balhae, thus unifying the two successor nations of Goguryeo.