The Roman Catholic faith came to Korea at the beginning of the 17th century, primarily through the work of lay catechists. The strong and dynamic Catholic communities were led almost entirely by lay people until the arrival of the first French missionaries in 1836. The Catholic community suffered major persecutions in the years 1839, 1846 and 1866, producing at least 103 known martyrs. Among them were the fervent Korean priest Andrew Kim Taegŏn and the Korean lay catechist Paul Chŏng Hasang. The vast majority of the martyrs were simple lay people, including men and women, married and single, old and young. The group has been canonized as saints, with feast day September 20.

From the last letter of Andrew Kim Taegŏn to his parish as he awaited maryrdom with a group of twenty persons:

My dear brothers and sisters, know this: Our Lord Jesus Christ upon descending into the world took innumerable pains upon and constituted the holy Church through his own passion and increases it through the passion of its faithful....

Now, however, some fifty or sixty years since holy Church entered into our Korea, the faithful suffer persecutions again. Even today persecution rages, so that many of our friends of the same faith, among whom am I myself, have been thrown into prison. just as you also remain in the midst of persecution. Since we have formed one body, how can we not be saddened in our innermost hearts? How can we not experience the pain of separation in our human faculties?

However, as Scripture says, God cares for the least hair of our heads, and indeed he cares with his omniscience; therefore, how can persecution be considered as anything other than the command of God, or his prize, or precisely his punishment?...

We are twenty here, and thanks be to God all are still well. If anyone is killed, I beg you not to forget his family. I have many more things to say, but how can I express them with pen and paper? I make an end to this letter. Since we are now close to the struggle, I pray you to walk in faith, so that when you have finally entered into Heaven, we may greet one another. I leave you my kiss of love.