Cochin China (kōˈchĭn, kŏˈ–) [key], Fr. Cochinchine, historic region (c.26,500 sq mi/68,600 sq km) of Vietnam, SE Asia. The capital and chief city was Saigon (now Ho Chi Minh City). Cochin China was bounded by Cambodia on the northwest and north, by the historic region of Annam on the northeast, by the South China Sea on the east and south, and by the Gulf of Thailand on the west. It included the rich Mekong delta, one of the world's great rice-growing regions, and, in the northeast, the southern spurs of the Annamese Cordillera, where rubber, coffee, tea, oil palm, and sugarcane plantations were established. Only the Plaine des Joncs [reed plain] and the mangrove-covered Ca Mau peninsula were not cultivated. Cochin China was originally part of the Khmer Empire. In the 17th cent. the Annamese (later called Vietnamese) gradually infiltrated through the mouths of the Mekong, increasing their commercial influence until they became masters of the region in the middle of the 18th cent. After the French occupied Saigon (1859), Annam ceded to France both E Cochin China (1862) and W Cochin China (1867). Unlike the other sections of Indochina, which were French protectorates under native rulers, Cochin China was administered by the French as a colony; thus, French influence was strongest there. After World War II the status of Cochin China became a major issue in the relations between France and Vietnam. Constituted (1946) as an independent republic within the Federation of Indochina, Cochin China was later (1949) permitted by the French to join with Annam and Tonkin in Vietnam. After 1954, when Vietnam was partitioned, Cochin China became the heartland of South Vietnam; it was later divided into several provinces.