Prior to the introduction of Buddhism, all Koreans believed in their indigenous religion socially guided by mu (shamans). Buddhism was introduced from the Chinese Former Qin state in 372 to the northern Korean state of Goguryeo[17][not in citation given] and developed into distinctive Korean forms. At that time, the peninsula was divided into three kingdoms: the aforementioned Goguryeo in the north, Baekje in the southwest, and Silla in the southeast. Buddhism reached Silla only in the 5th century, but it was made the state religion only in that kingdom in the year 552.[17] Buddhism became much more popular in Silla and even in Baekje (both areas comprehended in modern South Korea), while in Goguryeo the Korean indigenous religion remained dominant.
In the following unified state of Goryeo (918–1392) Buddhism flourished, and even became a political force.[18] However, in the same period, influences from Chinese Confucianism led to the formation of Korean Confucianism that would have become the state ideology and religion of the following Joseon state.[citation needed]
The Joseon kingdom (1392–1910), strictly Neo-Confucian, harshly suppressed Korean Buddhism[19][20] and Korean shamanism.[3] Buddhist monasteries were destroyed and their number dropped from several hundreds to a mere thirty-six; Buddhism was eradicated from the life of towns as monks and nuns were prohibited from entering them and were marginalised to the mountains.[20] These restrictions lasted until the 19th century.[21]
In the late 19th century, the Joseon state was politically and culturally collapsing.[22] The intelligentsia was looking for solutions to invigorate and transform the nation.[22] It was in this critical period that they came into contact with Western Protestant missionaries who offered a solution to the plight of Koreans.[22] Christian communities already existed in Joseon, however it was only by the 1880s that the government allowed a large number of Western missionaries to enter the country.[23] Protestant missionaries set up schools, hospitals and publishing agencies.[24] The king of Korea and his family tacitly supported Christianity.[5]
During the absorption of Korea into the Japanese Empire (1910–1945) the already formed link of Christianity with Korean nationalism was strengthened,[6] as the Japanese tried to impose State Shinto and Christians refused to take part in Shinto rituals.[6] At the same time, numerous religious movements that since the 19th century had been trying to reform the Korean indigenous religion, notably Cheondoism, flourished.[25]