French gunships under Charles Rigault de Genouilly attack the port of Da Nang in 1858 under the orders of Napoleon III of France, causing significant damages yet failing to gain any foothold.

De Genouilly decides to sail south.

Nguyen Anh—the Vietnamese emperor Gia Long—had tolerated Catholicism and employed some Europeans in his court as advisors after establishing the Nguyen Dynasty in 1802.

However, he and his successors have been conservative Confucians who have resisted Westernization.

The next Nguyen emperors, Ming Mang, Thieu Tri, and Tu Duc, had brutally suppressed Catholicism and pursued a "closed door" policy, perceiving the Westerners as a threat.

Tens of thousands of Vietnamese and foreign-born Christians were persecuted and trade with the West slowed during this period.

These acts were soon being used as excuses for France to invade Vietnam.

The early Nguyen Dynasty had actually accomplished almost everything the previous great Vietnamese dynasties did (like building roads, digging canals, issuing legal code, holding examinations, sponsoring caring facilities for the sick, compiling maps and history books, exerting influence over Cambodia and Laos, etc.), except that these feats are not enough in the new age of science, technology, industrialization, and international trade and politics. (The Nguyen Dynasty is usually blamed for failing to modernize the country in time to prevent French colonization in late nineteenth century.)