Peace & War: The Unification of the Korean Peninsula

Have you heard of the phrase “all good things must come to an end”? Everyone questions why, but they never think about what happens next. The truth is, life is full of trial and error. Sometimes you need to start from scratch and use past experience to build something greater. We’ve discussed the legend of Dangun, who created the Korean legacy, and the Three Kingdoms of Korea, where customs and traditions inspired by neighboring kingdoms were developed. However, throughout the rise of these kingdoms and their cultures, war was a predominant cause of their fall. In other words, many great kingdoms were destroyed at their height, but little did the Korean Peninsula know that one particular war would influence the unification of several Korean kingdoms.

Photo: Republic of Korea

Balhae (발해)

From 698 to 926 C.E., Balhae was a flourishing kingdom established by former military general Dae Joyeong (대조영), or King Go of Balhae (발해고왕), who was from the late Goguryeo (고구려) Kingdom. After his parents were killed by the Wu Zhou, the king created an army of Goguryeo and Mohe tribes to fight against Li Kaigu, a Khitan commander of the Chinese Tang and Zhou Dynasties. This was known as the Battle of Tianmenling or the Battle of Cheonmunryeong (천문령 전투). Following Dae Joyeong’s win, the young king crowned himself the King of Jin (진), building the capital on Dongmo Mountain, now modern Dunhua (돈화) located in the Jilin Province. The king later reconciled with the two dynasties, tried to bring his political stance to nearby kingdoms, and renamed his kingdom Balhae. However, this peace did not last as the soon-to-be Unified Silla (통일신라) allied with the Tang Dynasty to overthrow what was left of Goguryeo. Balhae was hostile toward Silla even after the king died, with his son Dae Muye (대무예), or King Mu (무왕) staying unremitting, as were many future kings.

Balhae occupied space across the Korean Peninsula, Taedong River (대동강, the largest river in North Korea), Liaoning, Jilin, Heilongjiang; the three provinces of Northeast China; and the Maritime Province of Russia (Primorsky Krai). In fact, Balhae had so much territory that it often changed its capital city. The five capitals had their own cultures that were shared throughout the kingdom, forming an advanced civilization that was praised by China as the “thriving nation of the Eastern Sea.” However, Sanggyeong (상경), Junggyeong (중경), and Donggyeong (동경) were especially known because of their intricate architecture and delicate artwork, specifically roof tiles, dragon heads, and Buddhist sculptures. The kingdom maintained its alliances with Silla, China, and Japan by exchanging items like these. This would unknowingly save many of its citizens' lives after its fall due to the Baekdu Mountain (백두산) erupting and an invasion of the Khitan people.

Photo: gorekun

Unified Silla (통일신라)

Unified Silla was an affluent, robust kingdom from 676 to 935 C.E. Their power only grew after allying with the Tang dynasty, enabling it to conquer Baekje (백제) and Goguryeo, forming unification. Silla occupied space from the south of Taedong River to Wonsan Bay (원산), a city in the Gangwon Province (강원도) in North Korea. But how did this alliance start? First, we need to discuss the territorial expansion and unification of multiple kingdoms.

During the Fifth Century, all three kingdoms on the Korean Peninsula were forced to give up parts of their land due to territorial expansion ordered by the governments and the king. As a result of this new policy, Goguryeo constructed a vast empire in Manchuria and on the Korean Peninsula, gaining much power in Northeast Asia. After Baekje lost its territory, the kingdom focused on rebuilding its strength and finding new land, but this was only possible by way of reinforcing its alliance with Silla. The kings worked together to improve local control to become a more advanced kingdom. The ruling system was reformed after moving Baekje’s capital, and the alliance proved worthy after the kingdom’s territory was regained. Silla had reformed its political system in the Sixth Century, also changing its name to Silla. The kingdom acquired nearby islands Ulleungdo (울릉도) and Dokdo (독도) in 512 C.E. and wanted to secure its development by changing the ruling system, such as clothing and adopting a religion. They further took Gaya (가야) and established the Hwarangdo (화랑도) to fight for and guard their expanded kingdom. Although Baekje had regained its land, Silla stole the land along the Hangang River (한강, the fourth longest river in the Korean Peninsula), and conquered Daegaya (대가야), the land along the Nakdonggang River (낙동강, the longest river in South Korea), and territory up to Hamheung (함흥, a city in North Korea) along the east coast.

At the time, Goguryeo was still the largest Korean kingdom but met a dark fate in 612 C.E. when the Sui Dynasty attacked the kingdom, known as the Battle of Salsu (살수대첩). The dynasty unified all of Mainland China into one state, which enabled it to grow an army of more than a million soldiers. General Eulji Mundeok of Goguyeo (을지문덕 장군) drowned the majority of Chinese soldiers in the Salsu River, now Cheongcheongang River (청천강, a river in North Korea). The short-lived dynasty sustained massive damage and was unable to continue, falling into the control of the Tang Dynasty. Unfortunately for Goguryeo, the Tang Dynasty also attacked the kingdom several times but continuously failed. Simultaneously, Baekje repeatedly attacked Silla, and Goguryeo refused to help Silla counteract. However, the Tang Dynasty agreed to help, and the two quickly formed an alliance and invaded Baekje. Kim Yusin (김유신) led Silla soldiers and defeated Gyebaek’s (계백) elite Baekje army in Hwangsanbeol (황산벌), continuing to the kingdom’s capital Sabi (사비). Soldiers from the Tang Dynasty invaded through the estuary of the Geumgang River (금강, the third longest river in South Korea). Unable to counterattack, Baekje was forced to surrender to Silla-Tang in 660.

Eventually, the majority of the surrounding kingdoms were conquered by Silla, and its alliance with the Tang Dynasty only grew stronger. With a thirst for power, they together invaded Goguryeo. Although the kingdom was once the most powerful in Northeast Asia, it was still recovering from two previous wars against two dynasties of China at the time. It seemed the kingdom could not face another war, leading to its fall in 668 C.E. Silla was now one big kingdom thanks to its alliance with the Tang Dynasty, but little did the kingdom know about the betrayal yet to happen. Tang China was still hungry for power, and now that it had helped Silla conquer many kingdoms on the Korean Peninsula, the dynasty decided to take them for itself. Tang China established the Ungjin Commandery (웅진천도) in Baekje, the Protectorate-General to Pacify the East in Goguryeo, and the Gyerim Territory Area Command (계림) in Silla. However, Silla pursued a war against Tang China, destroying its navy in Gibeolpo (기벌포) near the estuary of the Geumgang River. From there, the kingdom effectively chased away Tang China from the entirety of the Korean Peninsula and proceeded to unify it in 676.

Unified Silla’s capital city, Gyeongju (경주시), became a castle town that organized and controlled neighboring settlements. The capital grew to become an international city after arranging an agreement with Southwest Asia, the Tang Dynasty, and Japan. From there, there were many exchanges between traders, monks, and Confucian scholars that gave other kingdoms ginseng and gold and silver artifacts. Silla saw books, ceramic ware, satin silk fabric, clothes, and craftwork products. However, prominent seaports, such as Ulsan (울산) and Danghangseong (당항성, now modern Hwaseong (화성) in Gyeonggi Province (경기도)), were often under attack by pirates wanting to steal these precious items. In the early Ninth Century, Jang Bogo (장보고), or General Jang Bogo of Silla (장보고 장군), created a forward base in Cheonghaejin (청해진, now present-day Wando (완도) in Jeollanamdo (전라남도)), to maintain safe trading and even work more with China and Japan.

But what about the kingdom’s societal growth? As Gyeongju’s advanced culture was being integrated with others, Buddhism became a leading religion that forever changed Korean civilization. This spanned across architecture, such as the Bell of King Seongdeok (성덕대왕신종) or Emille Bell, to funerals, such as using cremation and burial urns instead of tombs.

Unified Silla continued to grow, becoming an advanced, peaceful kingdom for all to see for more than a hundred years. That is until its own people fought back against the aristocracy and brought the kingdom back down to its knees. But you’ll have to wait until next month to discover that story.

Edited by Asia Moore