Buddhism was adopted as the official state religion in the Goguryeo, Silla and Baekje kingdoms during the Three Kingdoms Period (57 B.C.E. – 668 C.E.), and the Unified Silla kingdom(668-935) succeeded in applying Buddhism as the psychological force for the unification of the peninsula.
During the Unified Silla Period, Buddhism played a preeminent role in cultural development, resulting in the construction of such world-renowned historical sites as Bulguksa Temple and Sokguram Grotto.
In addition, the world's earliest known printing using woodblocks for the Mugujeonggwang Dharani followed by the first metal type print for the Jikjisimcheyojeol(Jikji in short), a Buddhist sutra, at Heungdeoksa Temple (in today’s city of Cheongju) attest the advanced development of the culture.
Pre-dating Guttenberg by 78 years, the text was printed in 1377 C.E. and it is currently in the possession of the French National Library. It was designated a UNESCO “Memory of the World” in 2001.
The sutra is an outline of Buddhist teachings necessary for spiritual development as well as indications as to how to pass on the Dharma, including religious songs, chanting, engravings, writings, glossaries of technical terms, and Seon verbal combat. During the Unified Silla Period, the teachings of Chan (known as Zen in Japanese and Seon in Korean) were brought from China and led to the development of a Seon order, thereby adding another dimension to philosophical advance and eventually providing a psychological foundation for the post-Silla period, the Goryeo Dynasty (918-1392).
Goryeo, too, adopted Buddhism and it became a unifying factor and the grounds for further national and cultural flourishing. In particular, Goryeo followed the teachings of Unified Silla National Monk Doseon (827-898) and had temples built on famous mountains around the nation, adding further impetus to the dissemination of the Dharma. Also during Goryeo, the Tripitaka Koreana was carved into more than 80,000 woodblocks as an offering for national protection from outside forces and invasion, and Buddhism gave birth to such creative national festivals as the P'algwanhoe and the Yeondeunghoe (Lotus Lantern Festival).
During Goryeo, the number of Buddhist orders diversified and flourished. However, the increasing economic and political influence of the monks led to condemnation by the common people, and, ignored by the aristocracy, Buddhism came into a period of political repression with the ensuing Joseon Dynasty (1392-1910).
During Joseon, Neo-Confucianism rapidly gained favor, and although royalty continued to practice Buddhism privately, Confucianism ruled administration and society. Under a continuing policy of repression, Buddhism was banished to the mountains and monks were generally treated harshly. However, this banishment proved to be quite valuable to Buddhism in two respects: the temples became centers for the communal flourishing of Seon practice, and Buddhism established strong bonds with the common people.
During the first half of the 20th century, Korean Buddhism necessarily fell under the influence of Japanese Buddhism during the Japanese Occupation (1910-1945). It was only after liberation in 1945 that traditional Korean Buddhism could once again be established in the form of Korean Seon and that the Jogye Order to once more come to the fore.