Between 1615 and 1753, French traders also engaged in trade in Vietnam. The first French missionaries arrived in Vietnam in 1658, under the Portuguese Padroado. From its foundation, the Paris Foreign Missions Society under Propaganda Fide actively sent missionaries to Vietnam, entering Cochinchina first in 1664 and Tonkin first in 1666. Spanish Dominicans joined the Tonkin mission in 1676, and Franciscans were present in Cochinchina from 1719 to 1834. The Vietnamese authorities began to feel threatened by continuous Christianisation activities. Following the detention of several missionaries, the French Navy received approval from their government to intervene in Vietnam in 1843, with the aim of freeing imprisoned Catholic missionaries from a kingdom that was perceived as xenophobic. Vietnam’s sovereignty was gradually eroded by France in a series of military conquests between 1859 and 1885. At the Siege of Tourane in 1858, the French was aided by the Spanish (Using Filipino and Spanish troops from the Philippines) and perhaps some Tonkinese Catholics. After the 1862 Treaty and especially after the full conquest of Lower Cochinchina by France in 1867, the Văn Thân movement of scholar-gentry class arose and committed violence against Catholics across central and northern Vietnam.
Between 1862 and 1867, the southern third of the country became the French colony of Cochinchina. By 1884, the entire country had come under French rule, with the central and northern parts of Vietnam separated into the two protectorates of Annam and Tonkin. The three Vietnamese entities were formally integrated into the union of French Indochina in 1887. The French administration imposed significant political and cultural changes on Vietnamese society. A Western-style system of modern education introduced new humanist values into Vietnam. Most French settlers in Indochina were concentrated in Cochinchina, particularly in Saigon, and in Hanoi, the colony’s capital.
Guerrillas of the royalist Cần Vương movement massacred around a third of Vietnam’s Christian population during the colonial period as part of their rebellion against French rule. They were defeated in the 1890s after a decade of resistance by the Catholics in reprisal for their earlier massacres. Another large-scale rebellion, the Thái Nguyên uprising, was also suppressed heavily. The French developed a plantation economy to promote the export of tobacco, indigo, tea and coffee. However, they largely ignored the increasing demands for civil rights and self-government.
The French maintained full control over their colonies until World War II, when the war in the Pacific led to the Japanese invasion of French Indochina in 1940. Afterwards, the Japanese Empire was allowed to station its troops in Vietnam while permitting the pro-Vichy French colonial administration to continue. Japan exploited Vietnam’s natural resources to support its military campaigns, culminating in a full-scale takeover of the country in March 1945. This led to the Vietnamese Famine of 1945, which resulted in up to two million deaths.