French Cochinchina (sometimes spelled Cochin-China; ; , Hán tự: ) was a colony of French Indochina, encompassing the whole region of Lower Cochinchina or Southern Vietnam from 1862 to 1946. The French operated a plantation economy whose primary strategic product was rubber. After the end of Japanese occupation (1941–45) and the expulsion from Saigon of Communist-led nationalist Viet Minh in 1946, the territory was established by the French as the Autonomous Republic of Cochinchina, a controversial decision that helped trigger the First Indochina War. In a further move to deny the claims of the Democratic Republic of Vietnam declared in Hanoi by the Viet Minh in 1949, Cochinchina was formally united with Annam and Tonkin in the State of Vietnam within the French Union. Nam Kỳ originated from the reign of Minh Mạng of the Nguyễn dynasty, but became a name associated with the French colonial period and so Vietnamese, especially nationalists, prefer the term Nam Phần to refer to Southern Vietnam. History French conquest In 1858, under the pretext of protecting the work of French Catholic missionaries, which the imperial Vietnamese Nguyễn dynasty increasingly regarded as a political threat, French Admiral Charles Rigault de Genouilly, with the assistance of Spanish forces from the Philippines, attacked Tourane (present day Da Nang) in Annam. Early in 1859 he followed this up with an attack on Saigon, but as in Tourane was unable to seize territory outside of the defensive perimeter of the city. The Vietnamese Siege of Saigon was not lifted until 1861 when additional French forces were able to advance across the Mekong Delta. The Vietnamese conceded in 1862 and signed the Treaty of Saigon. This ensured the free practice of the Catholic religion; opened the Mekong Delta (and three ports in the north, in Tonkin) to trade; and ceded to France the provinces of Biên Hòa, Gia Định and Định Tường along with the islands of Poulo Condore. In 1867, French Admiral Pierre de la Grandière forced the Vietnamese to surrender three additional provinces, Châu Đốc, Hà Tiên and Vĩnh Long. With these three additions all of southern Vietnam and the Mekong Delta fell under French control. Consolidation of power In 1871 all the territories ceded to the French in southern Vietnam were incorporated as colony of Cochinchina, with Admiral Dupré as its first governor. In 1887, the colony became a confederal member of the Union of French Indochina.