In 1825, emperor Minh Mạng, the son and successor of Gia Long, prohibited foreign missionaries in Vietnam, on the grounds that they perverted the people. The prohibition proved largely ineffective, as missionaries continued their activities in Vietnam, and participated in armed rebellions against Minh Mạng, as in the Lê Văn Khôi revolt (1833–1835). He banned Catholicism completely, as well as French and Vietnamese priests (1833–1836), leading to persecutions of French missionaries. These included the martyrdom of Joseph Marchand in 1835 or Pierre Borie in 1838. These events served in France to stoke a desire among young men to intervene and protect the Catholic faith.