The practice of Christianity in Korea revolves around two of its largest branches, Protestantism and Catholicism, accounting for 8.6 million and 5.3 million members respectively. Roman Catholicism was first introduced during the late Joseon Dynasty period. In 1603, Yi Gwang-jeong, Korean diplomat, returned from Beijing carrying several theological books written by Matteo Ricci, a Jesuit missionary to China. He began disseminating the information in the books and the first seeds of Christianity were sown. In 1758 King Yeongjo of Joseon officially outlawed Catholicism as an evil practice. Roman Catholicism was again introduced in 1785 by Yi Seung-hun. Korean Christians were subject to persecution and hardship. Many were martyred, especially during the Catholic Persecution of 1801 and later. The Joseon Dynasty saw the new religion as a subversive influence and persecuted its earliest followers in Korea, culminating in the Catholic Persecution of 1866, in which 8,000 Catholics across the c