Later on, political divides due to the remnants of the 2 previous kingdoms of Goguryo and Baekje, led to the emergence of the new state of Goryeo in 918.
Goryeo a result of Civil wars, remained dominant of the Korean peninsula until 1392, regardless of the constant aggression's of the Northern Chinese tribes, the Yuan dynasty, and the Mongols. By the mid 14th century, Goryeo freed itself from the grip or over-lordship of the Yuan Chinese Dynasty.
The Mongols attacked and raided Goryeo for 30 years until eventually giving up the conquest and the Master Servant relationship so desired.
Towards the end of it's existence, Goryeo's nobility completely ignored the misery of it's people caused by constant Japanese pirates attacks and raids, capture and slave trade, on the peninsula.
In 1392, a military overthrow led to the newly Joseon Kingdom, basically a more modern political entity, that would rule the Korean peninsula, still through Monarchy, but with a prominent control of political parties, that were still in majority the nobility of the nation.
The same war driven Yuan and Ming dynasties influenced the overthrow of Goryeo for the new Joseon.
Joseon saw it's culture gradually separate from China, more so by the creation of it's own writing system in 1443: Hangul. Yes, until then, Koreans used the Chinese writing system to express their own language.
Unfortunately, it led to an ever increasing isolationism from the surrounding nations, and eventually from progress. Joseon however proved very crafty, by it's own development of firearms, explosives, and military ships, in order to fight of the constant attempts of invasion by the Japanese.
From Ming to the Qing, Joseon had to keep those Chinese dynasties from their grip and their tributary state system.
For five centuries, the name Joseon remained, until 1897, to be renamed the Korean Empire, in an attempt to prove it's independence from Chinese sphere of influence.