vessels entering Vietnamese harbours were ordered to be searched with extra care. All entries were to be watched "lest some masters of the European religion enter furtively, mix with the people and spread darkness in the kingdom." In an imperial edict, Christianity was described as the "perverse European" (practice) and accused of "corrupting the hearts of men". Between 1833 and 1838, seven missionaries were sentenced to death, amongst them Pierre Borie, Joseph Marchand, and Jean-Charles Cornay. He first attempted to stifle the spread of Christianity by attempting to isolate Catholic priests and missionaries from the populace. He asserted that he had no French interpreters after Chaigneau's departure and summoned the French clergy to Hue and appointed them as mandarins of high rank to woo them from their proselytising. This 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. Some of them obeyed the orders, but others disobeyed the order upon being released, and returned to their parishes and resumed preaching. Isolationist foreign policy Minh Mạng continued and intensified his father's isolationist and conservative Confucian policies. His father had rebuffed a British delegation in 1804 proposing that Vietnam be opened to trade; the delegation's gifts were not accepted and turned away. At the time, Vietnam was of no interest to the European powers, since most of the continent was engaged in the Napoleonic Wars. Nevertheless, Napoleon had seen Vietnam as a strategically important objective in the Anglo-French power struggle in Asia, as he felt that it would make an ideal base from which to contest the East India Company's foothold in the Indian subcontinent. With the restoration of the Bourbon monarchy and the final exile of Napoleon in 1815, the military scene in Europe quieted and French interest in Vietnam was revived. Jean-Baptiste Chaigneau, one of the volunteers of Pigneau de Behaine who had helped Gia Long in his quest for power, had become a mandarin and continued to serve Minh Mạng, upon whose ascension, Chaigneau and his colleagues were treated more distantly. He eventually left in November 1824. In 1825,