Buddhism has a long history on the Korean peninsula. Most scholars agree that it was introduced no later than the 4th century of the Common Era. There were several states on the peninsula at that time, often called the Three Kingdoms period. The 3 kingdoms in question were Shilla, Baekje and Goguryeo.
Map of the Korean peninsula in the Three Kingdoms period.
Shilla, centered at Gyeongju in the southwest, eventually overpowered the other kingdoms with Chinese help, thereby creating the 1st unitary state on the peninsula, usually called Unified Shilla in English. This kingdom, which flourished from the late 7th to the early 10th centuries, was firmly Buddhist at the elite level. The ruling family of Unified Shilla eventually weakened and lost the throne to the energetic general Wang Geon, who established the Goryeo dynasty, from whose name the modern word ‘Korea’ is derived.
During the Goryeo period (10th-14th centuries CE), Buddhism became the established religion of the state and consequently benefited from lavish royal and governmental patronage, which lead to a flowering of Buddhist arts and crafts. It also lead to the acquisition of vast amounts of land and slaves, as well as to political interference in national affairs by the senior clergy. Towards the end of the Goryeo dynasty's rule, the Buddhist hierarchy was perceived to be decadent and corrupt, giving rise to calls for reform from Neo-Confucian scholar-officials and their political supporters. When General Yi Song Gye overthrew the moribund Goryeo dynasty in 1392 and proclaimed himself the founder of Joseon dynasty as King Taejo, he installed Neo-Confucianism as the state ideology.
Portrait of King Taejo.
Official patronage of Buddhism was largely withdrawn and the ruling class of the land turned towards Neo-Confucian beliefs, practices and institutions. Thenceforth, Buddhism, its temples, its clergy, and its arts steadily diminished in status. The new regime built no Buddhist temples in its new capital, now known as Seoul, and even banned monks from the capital city, which helps to explain why most of Korea’s major historic temples are located in distant mountain valleys.