Baekje in the context of Samguk Sagi

Seoul, officially Seoul Special Metropolitan City, is both the capital and largest city of South Korea, and the largest city in the whole of Korea. The broader Seoul Metropolitan Area, encompassing Seoul, Gyeonggi Province and Incheon, emerged as the world's sixth largest metropolitan economy in 2022, behind New York, Tokyo, Los Angeles, Paris, and London, and hosts more than half of South Korea's population. Although Seoul's population peaked at over 10 million, it has gradually decreased since 2014, standing at about 9.6 million residents as of 2024. Seoul is the seat of the South Korean government.

Seoul's history traces back to 18 BC when it was founded by the people of Baekje, one of the Three Kingdoms of Korea. During the Joseon dynasty, Seoul was officially designated as the capital, surrounded by the Fortress Wall of Seoul. In the early 20th century, Seoul was occupied by the Empire of Japan, temporarily renamed "Keijō" ("Gyeongseong" in Korean). The Korean War brought fierce battles, with Seoul changing hands four times and leaving the city mostly in ruins. Nevertheless, the city has since undergone significant reconstruction and rapid urbanization.

South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and the Sea of Japan to the east. Like North Korea, South Korea claims to be the sole legitimate government of the entire peninsula and adjacent islands. It has a population of about 52 million, of which half live in the Seoul metropolitan area, the ninth most populous metropolitan area in the world; other major cities include Busan, Daegu, and Incheon.

The Korean Peninsula was inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early seventh century BC. From the mid first century BC, various polities consolidated into the rival kingdoms of Goguryeo, Baekje, and Silla. The lattermost eventually unified most of the peninsula for the first time in the late seventh century AD, while Balhae succeeded Goguryeo in the north. The Goryeo dynasty (918–1392) achieved lasting unification and established the basis for the modern Korean identity. The subsequent Joseon dynasty (1392–1897) generated cultural, economic, and scientific achievements and also established isolationism starting from the mid-17th century. The succeeding Korean Empire (1897–1910) sought modernization and reform but was annexed in 1910 into the Empire of Japan. Japanese rule ended following Japan's surrender in World War II, after which Korea was divided into two zones: the Soviet-occupied northern zone and the United States-occupied southern zone. After negotiations on reunification failed, the southern zone became the Republic of Korea in August 1948, while the northern zone became the communist Democratic People's Republic of Korea the following month.

Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in Asia in 1945, it has been politically divided at or near the 38th parallel between North Korea (Democratic People's Republic of Korea; DPRK) and South Korea (Republic of Korea; ROK). Both countries proclaimed independence in 1948, and the two countries fought the Korean War from 1950 to 1953. The region is bordered by China to the north and Russia to the northeast, across the Amnok (Yalu) and Duman (Tumen) rivers, and is separated from Japan to the southeast by the Korea Strait.

Known human habitation of the Korean peninsula dates to 40,000 BC. The kingdom of Gojoseon, which according to tradition was founded in 2333 BC, fell to the Han dynasty in 108 BC. It was followed by the Three Kingdoms period, in which Korea was divided into Goguryeo, Baekje, and Silla. In 668 AD, Silla conquered Baekje and Goguryeo with the aid of the Tang dynasty, forming Unified Silla; Balhae succeeded Goguryeo in the north. In the late 9th century, Unified Silla collapsed into three states, beginning the Later Three Kingdoms period. In 918, Goguryeo was resurrected as Goryeo, which achieved what has been called a "true national unification" by Korean historians, as it unified both the Later Three Kingdoms and the ruling class of Balhae after its fall. Goryeo, whose name developed into the modern exonym "Korea", was highly cultured and saw the invention of the first metal movable type. During the 13th century, Goryeo became a vassal state of the Mongol Empire. Goryeo overthrew Mongol rule before falling to a coup led by General Yi Seong-gye, who established the Joseon dynasty in 1392. The first 200 years of Joseon were marked by peace; the Hangul, the Korean alphabet was created and Confucianism became influential. This ended with Japanese and Qing invasions, which brought devastation to Joseon and led to Korean isolationism. After the invasions, an isolated Joseon experienced another nearly 200-year period of peace and prosperity, along with cultural and technological development. In the final years of the 19th century, Japan forced Joseon to open up and Joseon experienced turmoil such as the Kapsin Coup, Donghak Peasant Revolution, and the assassination of Empress Myeongseong. In 1895, Japan defeated China in the First Sino-Japanese War and China lost suzerainty over Korea and Korea was placed under further Japanese influence. In 1897, the centuries old Joseon was replaced by the Korean Empire with the Joseon's last king, Gojong, becoming the Emperor of the Korean Empire. Japan's further victory in the 1904–1905 Russo-Japanese War, expelled Russian influence in Korea and Manchuria. In 1905, the Korean Empire became a protectorate of the Empire of Japan. In 1910, the Empire of Japan officially annexed the Korean peninsula.

Unified Silla, or Late Silla, is the name often applied to the historical period of the Korean kingdom of Silla after its conquest of Goguryeo in 668 AD, which marked the end of the Three Kingdoms period. In the 7th century, a Silla–Tang alliance conquered Baekje in the Baekje–Tang War. Following the Goguryeo–Tang War and Silla–Tang War in the 7th century, Silla annexed the southern part of Goguryeo, unifying the central and southern regions of the Korean peninsula.

Unified Silla existed during the Northern and Southern States period at a time when Balhae controlled the north of the peninsula. Unified Silla lasted for 267 years until it fell to Goryeo in 935 during the reign of King Gyeongsun.

Goryeo (Korean: 고려; Hanja: 高麗; MR: Koryŏ; pronounced [ko.ɾjʌ]; Middle Korean: 고ᇢ롕〮, romanized: kwòwlyéy) was a Korean state founded in 918, during a time of national division called the Later Three Kingdoms period, that unified and ruled the Korean Peninsula until the establishment of Joseon in 1392. Goryeo achieved what has been called a "true national unification" by Korean historians as it not only unified the Later Three Kingdoms but also incorporated much of the ruling class of the northern kingdom of Balhae, who had origins in Goguryeo of the earlier Three Kingdoms of Korea. According to Korean historians, it was during the Goryeo period that the individual identities of Goguryeo, Baekje and Silla were successfully merged into a single entity that became the basis of the modern-day Korean identity. The name "Korea" is derived from the name of Goryeo, also romanized as Koryŏ, which was first used in the early 5th century by Goguryeo; Goryeo was a successor state to Later Goguryeo and Goguryeo.

Goryeo was established in 918 when general Wang Kŏn, after rising under the erratic Taebong ruler Kung Ye, was chosen by fellow generals to replace him and restore stability. Throughout its existence, Goryeo, alongside Unified Silla, was known to be the "Golden Age of Buddhism" in Korea. As the state religion, Buddhism achieved its highest level of influence in Korean history, with 70 temples in the capital alone in the 11th century. Commerce flourished in Goryeo, with merchants coming from as far as the Middle East. The capital in modern-day Kaesong, North Korea was a center of trade and industry. Goryeo was a period of great achievements in Korean art and culture.

Goguryeo (37 BC – 668 AD) (Korean: 고구려; Hanja: 高句麗; RR: Goguryeo; lit. high castle; Korean pronunciation: [ko̞.ɡu.ɾjʌ̹]; Old Korean: Guryeo) also later known as Goryeo (Korean: 고려; Hanja: 高麗; RR: Goryeo; lit. high and beautiful; Korean pronunciation: [ko.ɾjʌ]; Middle Korean: 고ᇢ롕〮, kwòwlyéy), was a Korean kingdom which was located on the northern and central parts of the Korean peninsula and the southern and central parts of modern-day Northeast China (Manchuria). At its peak of power, Goguryeo encompassed most of the Korean peninsula and large parts of Manchuria, along with parts of eastern Mongolia, Inner Mongolia, and modern-day Russia.

Along with Baekje and Silla, Goguryeo was one of the Three Kingdoms of Korea. It was an active participant in the power struggle for control of the Korean peninsula and was also associated with the foreign affairs of neighboring polities in China and Japan.

Silla ([ɕiɭ.ɭa]; Old Korean: 徐羅伐, Yale: Syerapel, RR: Seorabeol; IPA: [sʌɾabʌɭ]) was a Korean kingdom that existed between 57 BCE and 935 CE and was located on the southern and central parts of the Korean peninsula. Silla, along with Baekje and Goguryeo, formed the Three Kingdoms of Korea. Silla had the lowest population of the three, approximately 850,000 people (170,000 households), significantly smaller than those of Baekje (3,800,000 people) and Goguryeo (3,500,000 people).

Its foundation can be traced back to the semi-mythological figure of Hyeokgeose of Silla (Old Korean: *pulkunae, "light of the world"), of the Park clan. The country was first ruled intermittently by the Miryang Park clan for 232 years and the Wolseong Seok clan for 172 years and beginning with the reign of Michu Isageum the Gyeongju Kim clan for 586 years. Park, Seok and Kim have no contemporary attestations and went by the Old Korean names of 居西干 Geoseogan (1st century BCE), 次次雄 Chachaung (1st century CE), 泥師今 Isageum (Old Korean: *nisokum) and 麻立干 Maripkan (5th-6th century) instead.

Samguk yusa (Korean: 삼국유사; Hanja: 三國遺事; lit. Memorabilia of the Three Kingdoms) Korean pronunciation: [sʰam.ɡuk̚.ju.sa]) is a collection of legends, folktales, and historical accounts relating to the Three Kingdoms of Korea (Goguryeo, Baekje, and Silla), as well as to other periods and states before, during, and after the Three Kingdoms period. It was compiled by the Buddhist monk Il-yeon in the late Goryeo dynasty, around 1280, and was originally written in Classical Chinese. It is the earliest extant record of the Dangun legend, which records the founding of Gojoseon as the first Korean nation. Samguk yusa is National Treasure No. 306.

Samguk yusa is a history record composed of five volumes divided into nine parts. It documents various tales and legends which are categorized into two parts: historical events and Buddhist narratives. The text contains various historical narratives such as tales of the Three Kingdoms period, myths, legends, genealogies, histories, and Buddhist tales, which have helped maintain folklore from medieval Korea. "Yusa" is a term used to describe a text that is supplementary to an earlier work. Samguk yusa is intended to provide additional information to texts such as the Samguk sagi. The beginning of Samguk yusa describes Dangun Wanggeom, a mythological ancestor of all Koreans, founding the first nation of Korea, named Gojoseon. The text also contains several well-known tales such as "Choshin's Dream" and "Lady Suro".

The Proto–Three Kingdoms period (or Samhan period) refers to the proto-historical period in the Korean Peninsula, after the fall of Gojoseon and before the maturation of Goguryeo, Baekje, and Silla into full-fledged kingdoms. It is a subdivision of what is traditionally called Korea's Three Kingdoms period and covers the first three centuries of the Common Era, corresponding to the later phase of the Korean Iron Age.

Dongmyeong of Goguryeo (Korean: 동명성왕; Hanja: 東明聖王), personal name Ko Chumong (고주몽; 高朱蒙), was the founding monarch of the kingdom of Goguryeo, and was worshipped as a god-king by the people of Goguryeo and Goryeo. King Dongmyeong was also an important figure for the kingdom of Baekje, as the father of its founding monarch, King Onjo.

37°31′50.25″N 127°7′0.62″E / 37.5306250°N 127.1168389°E / 37.5306250; 127.1168389

Wiryeseong (Korean: 위례성; Hanja: 慰禮城) was the name of two early capitals of Baekje, one of the Three Kingdoms of Korea. Both are believed to have been in the modern-day Seoul area. According to the Samguk sagi (the oldest surviving Korean history books, written in the 12th century), Onjo, the son of Goguryeo's founder Jumong, founded the nation of Sipje (십제, 十濟; later became Baekje) on Wiryeseong in 18 BC, while his elder brother Biryu established himself in Michuhol (미추홀; 彌鄒忽) further to the west. The location of Michuhol is usually believed to be present-day Incheon.

Buyeo (Korean: 부여; Korean pronunciation: [pu.jʌ]; Chinese: 夫餘/扶餘; pinyin: Fūyú/Fúyú), also rendered as Puyŏ or Fuyu, was an ancient kingdom that was centered in northern Manchuria in modern-day northeast China. It had ties to the Yemaek people, who are considered to be the ancestors of modern Koreans. Buyeo is considered a major predecessor of the Korean kingdoms of Goguryeo and Baekje.

According to the Book of the Later Han, Buyeo was initially placed under the jurisdiction of the Xuantu Commandery, one of Four Commanderies of Han in the later Western Han. Buyeo entered into formal diplomatic relations with the Eastern Han dynasty by the mid-1st century AD as an important ally of that empire to check the Xianbei and Goguryeo threats. Jurisdiction of Buyeo was then placed under the Liaodong Commandery of the Eastern Han. After an incapacitating Xianbei invasion in 285, Buyeo was restored with help from the Jin dynasty. This, however, marked the beginning of a period of decline. A second Xianbei invasion in 346 finally destroyed the state excepting remnants in its core region; these survived as vassals of Goguryeo until their final annexation in 494.

Korean Buddhism began in the 4th century CE during the Three Kingdoms Period. Centuries after Buddhism originated in India, the Mahayana tradition arrived in China through the Silk Road in the 1st century CE, then entered the Korean peninsula in the 4th century, from where it was transmitted to Japan. In Korea, it was adopted as the state religion of 3 constituent polities of the Three Kingdoms Period, first by the Goguryeo (also known as Goryeo) in 372 CE, by the Silla (Gaya) in 528 CE, and by the Baekje in 552 CE.

Korean Buddhism is distinguished from other forms of Buddhism by its attempt to resolve what its early practitioners saw as inconsistencies within the Mahayana Buddhist traditions that they received from foreign countries. To address this, they developed a new holistic approach to Buddhism that became a distinct form, an approach characteristic of virtually all major Korean thinkers. The resulting variation is called Tongbulgyo ("interpenetrated Buddhism"), a form that sought to harmonize previously arising disputes among scholars (a principle called hwajaeng 和諍).

The Goguryeo–Tang War occurred from 645 to 668 and was fought between Goguryeo and the Tang dynasty. During the course of the war, the two sides allied with various other states. Goguryeo successfully repulsed the invading Tang armies during the first Tang invasions of 645–648. After conquering Baekje in 660, Tang and Silla armies invaded Goguryeo from the north and south in 661, but were forced to withdraw in 662. In 666, Yŏn Kaesomun died and Goguryeo became plagued by violent dissension, numerous defections, and widespread demoralization. The Tang–Silla alliance mounted a fresh invasion in the following year, aided by the defector Yŏn Namsaeng. In late 668, exhausted from numerous military attacks and suffering from internal political chaos, Goguryeo and the remnants of Baekje army succumbed to the numerically superior armies of the Tang dynasty and Silla.

The war marked the end of the Three Kingdoms of Korea period which had lasted since 57 BC. It also triggered the Silla–Tang War during which the Silla Kingdom and the Tang Empire fought over the spoils they had gained.