Pigneau de Béhaine (1741-1799)

Pierre Joseph Georges Pigneau, commonly known as Pigneau de Béhaine, also Pierre Pigneaux and Bá Đa Lộc, was a French Catholic priest best known for his role in assisting Nguyen Anh (later Emperor Gia Long) to establish the Nguyen dynasty in Vietnam after the Tay Son rebellion. Born in Aisne, he joined the Paris Foreign Mission Society and was assigned to Vietnam (then called Cochinchina) in 1765. While there he mastered both the Chinese and Vietnamese languages and wrote a Latin-Vietnamese dictionary. In 1774, he was named Apostolic Visitor with the rank of Bishop. He produced a catechism in Vietnamese. When the future Emperor Gia Long was facing a rebellion, Pigneau de Béhaine persuaded the French government to aid aid the young ruler. For many years he served as an advisor and unofficial foreign minister to the emperor. He tried for many years to convert him, but unsuccessfully.
(Adapted from Wikipedia)