French conquest of Vietnam

The French conquest of Vietnam¹ (1858–1885) was a series of military expeditions that pitted the Second French Empire, later the French Third Republic, against the Vietnamese empire of Đại Nam in the mid-late 19th century. Its end and results were victories for the French as they defeated the Vietnamese and their Chinese allies in 1885, the incorporation of Vietnam, Laos, and Cambodia, and finally established French rules over constituent territories of French Indochina over Mainland Southeast Asia in 1887.

A joint Franco-Spanish expedition was initiated in 1858 by invading Tourane (modern day Da Nang) in September 1858 and Saigon five months later. This four-year campaign resulted in King Tu Duc signing a treaty in June 1862, granting the French sovereignty over three provinces in the South. The French annexed the three southwestern provinces in 1867 to form Cochinchina. Having consolidated their power in Cochinchina, they conquered the rest of Vietnam through a series of campaigns in Tonkin between 1873 and 1886. French ambitions to subjugate Tonkin were opposed by the Qing dynasty, the region being part of the Chinese sphere of influence.

The French eventually drove most of the Chinese troops out of Vietnam, but remaining groups in some Vietnamese provinces continued to resist France's control over Tonkin. The French government sent Fournier to Tianjin to negotiate the Tianjin Accord, according to which China recognized the French authority over Annam and Tonkin, abandoning its claims to suzerainty over Vietnam. On June 6, 1884, Treaty of Huế was signed, dividing Vietnam into three regions: Tonkin, Annam, and Cochinchina, each under three different separate regimes. Cochinchina was a French colony, while Tonkin and Annam were protectorates, and the Nguyễn court was put under French supervision.