Confucianism was the first to arrive and began to be absorbed by the Kingdoms of Koguryo and Paekche in the 4th century AD. However, they did not become wholly Confucian societies They maintained their own cultural identities while adopting certain elements of the Confucian system of education and politics.
From this introduction, the standards of formalized Korean culture and statesmanship were raised considerably. During this time, the Confucian system of recording events in written form began, so this is the first period of Korean history which was formally recorded.
Under the guidance of the Confucian monk Sundo, King Sosurim of Koguryo, in 372 AD, established T'aehak, the first national college for the education of the aristocracy in his kingdom. Soon after this, he began opening private academies called Kyongdang. These schools were set up to educate the youth of the Koguryo aristocracy in the Confucian classics, Chinese literature, the healing arts, and the martial arts. These were the first formalized schools of martial arts on the Korean Peninsula. These academies were not open to the public but were solely for the privileged.