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 Later Silla, while Balhae controlled the northern parts of Goguryeo.
The new official name has its origin in the ancient country of Gojoseon (Old Joseon).
In 1897, the Joseon dynasty changed the official name of the country from Joseon to Daehan Jeguk (Korean Empire).
Since the government only controlled the southern part of the Korean Peninsula, the informal term South Korea was coined, becoming increasingly common in the Western world.
While South Koreans use Han (or Hanguk) to refer to the entire country, North Koreans and ethnic Koreans in China and Japan use the term Joseon as the name of the country.
After Japan's surrender in 1945, Korea was divided along the 38th parallel with the United States controlling the southern part.
This region was declared the First Korean Republic on August 15, 1948, but a North Korean invasion led to the Korean War (1950–1953) two years later.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.in the Goryeo–Khitan War, Goryeo experienced a golden age that lasted a century, during which the Tripitaka Koreana was completed and there were great developments in printing and publishing, promoting learning and dispersing knowledge on philosophy, literature, religion, and science; by 1100, there were 12 universities that produced famous scholars and scientists.However, the Mongol invasions in the 13th century greatly weakened the kingdom.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.