THE SOUTH OF VIETNAM (1955 to 1975)
Unlike the other French possessions in Indochina, which were nominally protectorates, the southern part of Vietnam was the colony of Cochin-China, which had its capital at Saigon. As a colony it occupied a different legal position from the protectorates of Annam and Tonkin; it had been annexed to France in 1862, and even elected a deputy to the French National Assembly. French colonial interests were thus stronger in Cochin-China than in other parts of French Indochina. As such, during the First Indochina War the French government initially attempted to keep the status of Cochin-China separate from that of the rest of Vietnam, even going so far as constituting it an independent republic within the Indochinese Federation in 1946, but this proved unacceptable to the Viet Minh and in 1949 Cochin-China was eventually reunited with the other parts of Vietnam.
The State of Vietnam was created through co-operation between anti-communist Vietnamese and the French government on June 14, 1949 during the First Indochina War, and the Emperor Bao Dai took up the position of Chief of State (Quoc Truong). This was known as the 'Bao Dai Solution', and was an attempt by the French to grant partial independence to Vietnam, while still retaining substantial control over the country, and keeping it from communist rule. Such a formulation was rejected by the communist Viet Minh, led by Ho Chi Minh, who were fighting the French for full independence for Vietnam.

In 1954 it was determined by the Geneva Conference that the State of Vietnam would rule the territory of Vietnam south of the 17th parallel, of which the former colony of Cochin-China formed the heartland, pending unification on the basis of supervised elections (see Geneva Conference (1954)) in 1956. The elections and unification did not take place as planned (see below). When the territory was divided in this way, approximately 800,000 to 1 million North Vietnamese, mainly Vietnamese Roman Catholics, fled south due to what they perceived as "communist persecution" in the North. The Republic of Vietnam was proclaimed in Saigon by Ngô Ðình Di?m on October 22, 1955, after the Emperor Bao Ð?i was deposed.
In accordance with the Paris Peace Accords signed with North Vietnam in 1973 all U.S. military forces withdrew from South Vietnam. Under the terms of the Accords North Vietnamese troops were not required to withdraw from South Vietnam. Taking advantage of the Southern government's lack of American aid, North Vietnam invaded South Vietnam in 1975, quickly capturing the cities of Hue, Da Nang and Da Lat in central Vietnam, and advancing southwards.
The Army of the Republic of Vietnam (ARVN) mounted a defense and a counterattack, but kept losing ground. South Vietnamese President Nguyen Van Thieu requested aid from U.S. President Gerald Ford, but the U.S. Senate would not release money to provide aid to South Vietnam, and had already passed laws to prevent further involvement in Vietnam.
Nguyen Van Thieu resigned on April 21, 1975, and fled to Taiwan. He nominated his Vice President Tran Van Huong as his successor. In one week, Tran Van Huong handed over the presidency to General Duong Van Minh, who tried, unsuccessfully, to open negotiations with the North. The North refused to negotiate an end to the war.
The Army of the Republic of Vietnam was unable to sustain the defense of South Vietnam and eventually collapsed, due to limited supplies of everything from food to ammunition to gasoline. Acting President Duong Van Minh unconditionally surrendered the capital city of Saigon and the rest of South Vietnam to North Vietnam on April 30, 1975.