Emperor Minh Mạng renames Việt Nam to Đại Nam in 1839.

In February 1825, Minh Mạng had banned missionaries from entering Vietnam.

French vessels entering Vietnamese harbors were ordered to be searched with extra care.

Between 1833 and 1838, seven missionaries had been sentenced to death, among them Pierre Borie, Joseph Marchand, and Jean-Charles Cornay.

Minh Mạng had first attempted to stifle the spread of Christianity by attempting to isolate Catholic priests and missionaries from the populace.

Asserted that he had no French interpreters after Jean-Baptiste Chaigneau's departure in 1826, he had summoned the French clergy to Hue and appointed them as mandarins of high rank to woo them from their proselytizing.

This had worked until a priest, Father Regereau, entered the country and began missionary work.

Following the edict which forbade further entry of missionaries into Vietnam, arrests of clerics began.

After strong lobbying by Duyệt, the governor of Cochin China, and a close confidant of Gia Long and Pigneau de Behaine, Minh Mạng agreed to release the priests on the condition that they congregate at Đà Nẵng and return to France.