Gija Joseon was purportedly founded in the 12th century BC, but its existence and role have been controversial in the modern era. Three of the commanderies fell or retreated westward within a few decades. As Lelang commandery was destroyed and rebuilt around this time, the place gradually moved toward Liadong. Goguryeo, the largest and most powerful among them, was a highly militaristic state,   and competed with various Chinese dynasties during its years of history.
Goguryeo experienced a golden age under Gwanggaeto the Great and his son Jangsu ,     who both subdued Baekje and Silla during their times, achieving a brief unification of the Three Kingdoms of Korea and becoming the most dominant power on the Korean Peninsula. Balhae was founded by a Goguryeo general and formed as a successor state to Goguryeo. Relationships between Korea and China remained relatively peaceful during this time.
Later Silla carried on the maritime prowess of Baekje , which acted like the Phoenicia of medieval East Asia ,  and during the 8th and 9th centuries dominated the seas of East Asia and the trade between China, Korea and Japan, most notably during the time of Jang Bogo ; in addition, Silla people made overseas communities in China on the Shandong Peninsula and the mouth of the Yangtze River.
In , the Later Three Kingdoms were united by Wang Geon , a descendant of Goguryeo nobility,  who established Goryeo as the successor state of Goguryeo. Goryeo was never conquered by the Mongols, but exhausted after three decades of fighting, the Korean court sent its crown prince to the Yuan capital to swear allegiance to Kublai Khan , who accepted, and married one of his daughters to the Korean crown prince.
During this period, the two nations became intertwined as all subsequent Korean kings married Mongol princesses,  and the last empress of the Yuan dynasty was a Korean princess.
However, in , General Yi Seong-gye , who had been ordered to attack China, turned his army around and staged a coup. Yi Seong-gye declared the new name of Korea as "Joseon" in reference to Gojoseon, and moved the capital to Hanseong one of the old names of Seoul.
Between and , Toyotomi Hideyoshi launched invasions of Korea , but his advance was halted by Korean forces most notably the Joseon Navy led by Admiral Yi Sun-sin and his renowned " turtle ship "      with assistance from Righteous Army militias formed by Korean civilians, and Ming dynasty Chinese troops. Through a series of successful battles of attrition, the Japanese forces were eventually forced to withdraw, and relations between all parties became normalized.
However, the Manchus took advantage of Joseon's war-weakened state and invaded in and , and then went on to conquer the destabilized Ming dynasty. After normalizing relations with the new Qing dynasty , Joseon experienced a nearly year period of peace. Kings Yeongjo and Jeongjo particularly led a new renaissance of the Joseon dynasty during the 18th century.
Furthermore, the Joseon government adopted a strict isolationist policy, earning the nickname "the hermit kingdom ", but ultimately failed to protect itself against imperialism and was forced to open its borders.
North Korea and South Korea. In the South, Syngman Rhee , an opponent of communism, who had been backed and appointed by the United States as head of the provisional government, won the first presidential elections of the newly declared Republic of Korea in May.
In the North, however, a former anti-Japanese guerrilla and communist activist, Kim Il-sung was appointed premier of the Democratic People's Republic of Korea in September. The UN declared Rhee's government as "a lawful government having effective control and jurisdiction over that part of Korea where the UN Temporary Commission on Korea was able to observe and consult" and the Government "based on elections which was observed by the Temporary Commission" in addition to a statement that "this is the only such government in Korea.
This allowed the UN to intervene in a civil war when it became apparent that the superior North Korean forces would unify the entire country. After an ebb and flow that saw both sides almost pushed to the brink of extinction, and massive losses among Korean civilians in both the north and the south, the war eventually reached a stalemate.
The armistice, never signed by South Korea, split the peninsula along the demilitarized zone near the original demarcation line. No peace treaty was ever signed, resulting in the two countries remaining technically at war. A period of political instability followed, broken by General Park Chung-hee 's May 16 coup against the weak and ineffectual government the next year. Park took over as president until his assassination in , overseeing rapid export-led economic growth as well as implementing political repression.
Park was heavily criticised as a ruthless military dictator, who in extended his rule by creating a new constitution , which gave the president sweeping almost dictatorial powers and permitted him to run for an unlimited number of six-year terms. However, the Korean economy developed significantly during Park's tenure and the government developed the nationwide expressway system , the Seoul subway system , and laid the foundation for economic development during his year tenure.
The years after Park's assassination were marked again by political turmoil, as the previously suppressed opposition leaders all campaigned to run for president in the sudden political void. On May 17, Chun Doo-hwan forced the Cabinet to expand martial law to the whole nation, which had previously not applied to the island of Jejudo. The expanded martial law closed universities, banned political activities and further curtailed the press.
Chun's assumption of the presidency in the events of May 17, triggered nationwide protests demanding democracy, in particular in the city of Gwangju , to which Chun sent special forces to violently suppress the Gwangju Democratization Movement. Chun and his government held South Korea under a despotic rule until , when a Seoul National University student, Park Jong-chul, was tortured to death.
Roh went on to win the election by a narrow margin against the two main opposition leaders, Kim Dae-Jung and Kim Young-Sam. Seoul hosted the Olympic Games in , widely regarded as successful and a significant boost for South Korea's global image and economy.
The transition of Korean from autocracy to modern democracy was marked in by the election of Kim Dae-jung , who was sworn in as the eighth president of South Korea, on February 25, His election was significant given that he had in earlier years been a political prisoner sentenced to death later commuted to exile. He won against the backdrop of the Asian Financial Crisis , where he took IMF advice to restructure the economy and the nation soon recovered its economic growth, albeit at a slower pace.
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". However, South Korean and Japanese relations later soured because of conflicting claims of sovereignty over the Liancourt Rocks.
Korea was the first chair of the G during the Seoul summit In , there was an escalation in attacks by North Korea. In November Yeonpyeong island was attacked by a significant North Korean artillery barrage, with 4 people losing their lives.
The lack of a strong response to these attacks from both South Korea and the international community the official UN report declined to explicitly name North Korea as the perpetrator for the Cheonan sinking caused significant anger with the South Korean public.
Daughter of another former president, Park Chung-hee , she carried on a conservative brand of politics. President Park Geun-hye's administration was formally accused of corruption, bribery, and influence-peddling for the involvement of close friend Choi Soon-sil in state affairs.
There followed a series of massive public demonstrations from November  and she was removed from office. His tenure so far has seen an improving political relationship with North Korea, some increasing divergence in the military alliance with the United States, and the successful hosting of the Winter Olympics in Pyeongchang.