Balhae in the context of "Unified Silla"

North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korean Peninsula and borders China and Russia to the north at the Yalu (Amnok) and Tumen rivers, and South Korea to the south at the Korean Demilitarized Zone (DMZ). The country's western border is formed by the Yellow Sea, while its eastern border is defined by the Sea of Japan. North Korea, like South Korea, claims to be the sole legitimate government of the Korean Peninsula and adjacent islands. Pyongyang is the capital and largest city.

The Korean Peninsula was first inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early 7th century BCE. Following the unification of the Three Kingdoms of Korea into Silla and Balhae in the late 7th century, Korea was ruled by the Goryeo dynasty (918–1392) and the Joseon dynasty (1392–1897). The succeeding Korean Empire (1897–1910) was annexed in 1910 into the Empire of Japan. In 1945, after the Japanese surrender at the end of World War II, Korea was divided into two zones along the 38th parallel, with the north occupied by the Soviet Union and the south occupied by the United States. In 1948, separate governments were formed in Korea: the socialist and Soviet-aligned Democratic People's Republic of Korea in the north, and the capitalist, Western-aligned Republic of Korea in the south. The North Korean invasion of South Korea in 1950 started the Korean War. In 1953, the Korean Armistice Agreement brought about a ceasefire and established a demilitarized zone (DMZ), but no formal peace treaty has ever been signed. Post-war North Korea benefited greatly from economic aid and expertise provided by other Eastern Bloc countries. However, Kim Il Sung, North Korea's first leader, promoted his personal philosophy of Juche as the state ideology. Pyongyang's international isolation sharply accelerated from the 1980s onwards as the Cold War came to an end. The fall of the Soviet Union in 1991 then brought about a sharp decline to the North Korean economy. From 1994 to 1998, North Korea suffered a famine with the population continuing to suffer from malnutrition. In 2024, the DPRK formally abandoned efforts to reunify Korea.

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.

The Liao dynasty (/ljaʊ/; Khitan: Mos Jælud; traditional Chinese: 遼朝; simplified Chinese: 辽朝; pinyin: Liáo cháo), also known as the Khitan State (Mos diau-d kitai huldʒi gur), officially the Great Liao (Chinese: 大遼; pinyin: Dà Liáo), was a Khitan-led imperial dynasty of China and empire ruled by the Yelü clan that existed between 916 and 1125. Founded around the time of the collapse of the Tang dynasty, at its greatest extent it ruled over Northeast China, the Mongolian Plateau, the northern part of the Korean Peninsula, southern portions of Siberia, and the northern tip of the North China Plain.

The dynasty rose from the consolidation of power among the Khitans in the 8th century and their expansionist campaigns in the latter half of the 9th century. Eventually the Yila chieftain, Abaoji, became the leader of the Khitans and proclaimed a Chinese-style dynastic state in 916. The Liao dynasty launched multiple military campaigns against neighboring states and peoples including the Kumo Xi, Shiwei, Tatars, Zubu, Khongirad, Balhae, Goryeo, Later Tang, and the Song dynasty. Its conquests include the Sixteen Prefectures (including present-day Beijing and part of Hebei) by fueling a proxy war that led to the collapse of the Later Tang (923–936). In 1004, the Liao launched an expedition against the Northern Song dynasty. After heavy fighting and large casualties between the two empires, both sides worked out the Chanyuan Treaty. Through the treaty, the Liao forced the Northern Song to recognize them as peers and heralded an era of peace and stability between the two powers that lasted approximately 120 years. It was the first state to control all of Manchuria.

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.