Đàng Trong
The West's exposure to Annam and Annamese exposure to Westerners dated back to 166 AD with the arrival of merchants from the Roman Empire, to 1292 with the visit of Marco Polo, and the early 16th century with the arrival of Portuguese in 1516 and other European traders and missionaries. Alexandre de Rhodes, a Jesuit priest from the Papal States, improved on earlier work by Portuguese missionaries and developed the Vietnamese romanized alphabet chữ Quốc ngữ in "Dictionarium Annamiticum Lusitanum et Latinum" in 1651. Jesuits in the 17th century established a firm foundation of Christianity in both domains of "Đàng Ngoài" (Tonkin) and "Đàng Trong" (Cochinchina). Various European efforts to establish trading posts in Vietnam failed, but missionaries were allowed to operate for some time until the mandarins began concluding that Christianity (which had succeeded in converting up to a tenth of the population by 1700) was a threat to the Confucian social order since it condemned ancestor worship as idolatry. Vietnamese authorities' attitudes to Europeans and Christianity hardened as they began to increasingly see it as a way of undermining society.