The first arrival and spread of Christianity in Korea began in the era of 16th century. During the period of the Joseon Dynasty, Roman Catholicism was introduced in Korea. Yi Gwang-Jeong, a Korean diplomat, first introduced Christianity in the year 1603, when he brought books from China based on Christian theologies. These were written by Matteo Ricci belonging to a Jesuit in China. He then disseminated the information and so got knowledge of the religion Christianity, This is how Christianity was first introduced.
During those late centuries, people were more racist and strict on matters in which they felt their religion, state, or culture was questioned and so thought their practices would be harmed. The people in the Korean peninsula thought likewise, and in 1758, King Yeongjo of Joseon banned the practice of Catholicism and called it to be an evil practice. In 1785, it was reintroduced by Yi Seung-hun, though the toleration level of this new religion then was quite low.
During the 18th century, especially in the year 1801, Catholic persecution began. The Joseon Dynasty saw Christianity as a threat to their existence and so began mass execution of Christians and subjected its earliest followers to killings, hardships and torture. In 1866 about 8,000 Christians were killed and 9 French missionaries were destroyed. Then later, Korea introduced itself to the whole world and so bared tolerance towards people of other religions.
Then came the time of Protestantism and so its first mission was opened by Horace Newton Allen in 1884 and remained in Korea till 1890, during which many had joined it. Gradually the two sects of Christianity grew and in 1945 about 2% of the population was Christian. The year 1991 was the most favorable for the growth of Christianity in Korea as about 8 million of the population was Protestants and 2.5 million was Catholic.
In South Korea Christianity is favored due its stress on humanitarian laws and promotion of education. The Christians started 293 schools and 40 universities of which 3 became one of the top institutes. Protestantism is most liked as it has a touch of modernism and attracts the middle class, youth, students, intellectuals and urbanites. Every ten years the Christian population doubles in South Korea.