The French missionaries in Vietnam step up their pressure on the French government to intervene militarily and to establish a French protectorate over Vietnam.

During this period, French traders become interested in Vietnam once more, and French diplomats in China begin to express the view that France is falling behind the rest of Europe in gaining a foothold in Asia.

Commanders of a French naval squadron, permanently deployed in the South China Sea after 1841, also begin to agitate for a stronger role in protecting the lives and interests of the missionaries.

Given tacit approval by Paris, naval intervention grows steadily.

In 1847 two French warships bombard Tourane (Da Nang), destroying five Vietnamese ships and killing an estimated ten thousand Vietnamese.

The purpose of the attack is to gain the release of a missionary, who had, in fact, already been released.

In the following decade, persecution of missionaries will continue under Emperor Tu Dus, who comes to the throne in 1848.

While the missionaries step up pressure on the government of Louis Napoleon (later Napoleon III), which is sympathetic to their cause, a Commission on Cochinchina makes the persuasive argument that France risks becoming a second-class power by not intervening.