Cochinchina campaign in the context of "French Cochinchina"

French Indochina (previously spelled as French Indo-China), officially known as the Indochinese Union and after 1941 as the Indochinese Federation, was a group of French dependent territories in Southeast Asia from 1887 to 1954. It was initially a federation of French colonies (1887–1949), later a confederation of French associated states (1949–1954). It comprised Cambodia, Laos (from 1899), Guangzhouwan (1898–1945), Cochinchina, and Vietnamese regions of Tonkin and Annam. It was established in 1887 and was dissolved in 1954. In 1949, Vietnam was reunited and it regained Cochinchina. Its capitals were Hanoi (1902–1945) and Saigon (1887–1902, 1945–1954).

The Second French Empire colonized Cochinchina in 1862 and established a protectorate in Cambodia in 1863. After the French Third Republic took over northern Vietnam through the Tonkin campaign, the various protectorates were consolidated into one union in 1887. Two more entities were incorporated into the union: the Laotian protectorate and the Chinese territory of Guangzhouwan. The French exploited the resources in the region during their rule, while also contributing to improvements of the health and education system in the region. Deep divides remained between the native population and the colonists, leading to sporadic rebellions by the former.

The French conquest of Vietnam (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 results were victories for France as they defeated the Vietnamese and their Chinese allies in 1885, incorporated modern-day Vietnam, Laos, and Cambodia into the French colonial empire, and established the territory 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 Emperor 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 Treaty of Saigon (French: Traité de Saïgon, Vietnamese: Hòa ước Nhâm Tuất, referring to the year of "Water Dog" in the sexagenary cycle) was signed on 5 June 1862 between representatives of the colonial powers, France and Spain, and the last precolonial emperor of the Nguyễn dynasty, Emperor Tự Đức after the coalition's invasion during the Cochinchina campaign. The signatories were Louis Adolphe Bonard (France), Carlos Palanca Gutiérrez (Spain) and Phan Thanh Giản (Vietnam). Based on the terms of the accord, Tự Đức ceded Saigon, the island of Poulo Condor and three southern provinces of what was to become known as Cochinchina (Bien Hoa, Gia Dinh, and Dinh Tuong) to the French. The treaty was confirmed by the Treaty of Huế signed on 14 April 1863.