In the early centuries of the Common Era, Buyeo, Okjeo, Dongye, and the Samhan confederacy occupied the peninsula and southern Manchuria. Of the various small states, Goguryeo, Baekje, and Silla grew to control the peninsula as the Three Kingdoms. The unification of the Three Kingdoms by Silla in 676 led to the North-South States period, in which much of the Korean peninsula was controlled by Unified Silla, while Balhae succeeded the northern parts of Goguryeo. In Unified Silla, poetry and art was encouraged, and Buddhist culture flourished. Relationships between Korea and China remained relatively peaceful during this time. However, Unified Silla weakened under internal strife, and surrendered to Goryeo in 935. Balhae, Silla's neighbor to the north, was formed as a successor state to Goguryeo. During its height, Balhae controlled most of Manchuria and parts of Russia. It fell to the Khitan in 926.
After the North-South Period, successor states fought for control during the Later Three Kingdoms period. The peninsula was soon united by Emperor Taejo of Goryeo. Like Silla, Goryeo was a highly cultural state and created the Jikji in 1377, using the world's oldest movable metal printing press.
The Mongol invasions in the 13th century greatly weakened Goryeo. However, Goryeo continued to rule Korea as a tributary ally to the Mongols. After the fall of the Mongolian Empire, Goryeo continued its rule. After severe political strife and continued invasions, Goryeo was replaced by the Joseon Dynasty in 1388 following a rebellion by General Yi Seong-gye. General Li declared the new name of Korea as Joseon in reference to Gojoseon, and moved the capital to Seoul. The first 200 years of the Joseon Dynasty was marked by relative peace and saw the creation of hangul by Sejong the Great in the 14th century and the rise and influence of Confucianism.
In the latter of the 16th century, Joseon was invaded by a newly unified Japan. During the Japanese invasions of Korea (1592–1598), centuries of peace had left the dynasty unprepared, and the lack of technology and poor leadership from the Joseon government and generals led to the destruction of much of the Korean peninsula. In the first Japanese invasion (1592–1593), the army sent from China to assist Korea had a prescribed strength of 100,000, including 42,000 from five northern military districts and a contingent of 3,000 soldiers proficient in the use of firearms from South China. In the second Japanese invasion (1597–1598), Chinese army and navy involved were around 75,000 at the climax of the second campaign. In comparison, Japan's invasion army was depleted from 167,700 in the first invasion to 122,100 in the second invasion. Though outnumbered by the Japanese invasion force, however, continued Korean dominance at sea led by Admiral Yi, the rise of local militias, and the intervention of Ming China put Japan under great pressure to retreat in 1598.
Between the years 1607 and 1811, Joseon sent Tongsinsa(royal embassies) to Japan for the diplomatic exchange between two countries, and before the Japanese invasions of Korea (1592–1598) it was to make formal requests to the shogun to take control of waegu (J: wakō), or "Japanese pirates", which ravaged and plundered along Joseon’s coastline. During the last years of the Joseon Dynasty, Korea's isolationist policy earned it the name the "Hermit Kingdom", primarily for protection against Western imperialism before it was forced to open trade beginning an era leading into Japanese colonial rule.
In the aftermath of World War II, Soviet Union and United States troops controlled the northern and southern halves of the country respectively.
Despite the initial plan of a unified Korea in the 1943 Cairo Declaration, escalating Cold War antagonism eventually led to the establishment of two separate governments, each with its own ideology, leading to Korea's division into two political entities: North Korea and South Korea. In the North, a former anti-Japanese guerrilla and communist activist, Kim Il-sung, and in the South, an exiled Korean political leader, Syngman Rhee, were installed as presidents.
On 25 June 1950, North Korea invaded the South leading to the Korean War. At the time, the Soviet Union boycotted the United Nations (UN), thus forfeiting their veto rights. This allowed the UN to intervene when it became apparent that the superior communist forces would easily take over the entire country. The Soviet Union and China backed North Korea, with the later participation of millions of Chinese troops. After huge advances on both sides, the war eventually reached a stalemate. The 1953 armistice, never signed by South Korea, split the peninsula along the demilitarized zone near the original demarcation line. No peace treaty was ever signed at the time of the armistice, resulting in the two countries remaining technically at war. At least 2.5 million people died during the Korean War.
In 1960, a student uprising led to the resignation of the autocratic President Syngman Rhee. A period of political instability followed, broken by General Park Chung-hee's military coup (the "5-16 coup d'état") against the weak and ineffectual government the next year. Park took over as president until his assassination in 1979, overseeing rapid export-led economic growth as well as severe political repression. Park was heavily criticised as a ruthless military dictator, although the Korean economy developed significantly during his tenure.
The years after Park's assassination were marked again by considerable political turmoil as the previously repressed opposition leaders all campaigned to run for president in the sudden political void. In 1980 there was another coup d'état by General Chun Doo-hwan against the transitional government of Choi Gyu Ha, the interim president and a former prime minister under Park. Chun assumed the presidency. His seizure of power triggered nationwide protests demanding democracy, in particular in the city of Gwangju, in Jeollanam-do, where Chun sent special forces to violently suppress the unrest, in what is now known as the Gwangju Massacre.
Until 1987, Chun and his government held Korea under a despotic rule when Park Jong Chul — a student attending Seoul National University — was tortured to death. On 10 June, the Catholic Priests' Association for Justice revealed Park's torture, igniting huge demonstrations around the country. Eventually, Chun's party, the Democratic Justice Party, and its leader, Roh Tae-woo announced the June 29th Declaration, which included the direct election of the president. Roh went on to win the election by a narrow margin against the two main opposition leaders, Kim Dae-Jung and Kim Young-Sam.
In 1988, Seoul successfully hosted the 1988 Summer Olympics, and continuing economic development led to membership in the Organisation for Economic Co-operation and Development (OECD) in 1996. As with many of its Asian neighbors, South Korea was adversely affected by the 1997 Asian Financial Crisis, however the country was able to recover and continue its economic growth.
In June 2000, as part of president Kim Dae-Jung's Sunshine Policy' of engagement, a North-South summit took place in Pyongyang, the capital of North Korea. Later that year, Kim received the Nobel Peace Prize "for his work for democracy and human rights in South Korea and in East Asia in general, and for peace and reconciliation with North Korea in particular."
In 2002, South Korea and Japan jointly co-hosted the 2002 FIFA World Cup, however South Korean and Japanese relations later soured due to conflicting claims of sovereignty over the Dokdo Islets (also known as the Liancourt Rocks), in what became known as the Liancourt Rocks dispute.