[4] In 1949, during the First Indochina War, the French formed the State of Vietnam, a rival government of anti-communist Vietnamese politicians in Saigon, led by former emperor Bảo Đại.

A 1955 referendum on the state's future form of government was widely marred by electoral fraud and resulted in the deposal of Bảo Đại by Prime Minister Ngô Đình Diệm, who proclaimed himself president of the new republic on 26 October 1955.

A regular bombing campaign over North Vietnam was conducted by offshore US Navy airplanes, warships, and aircraft carriers joined by Air Force squadrons through 1966 and 1967.

An even larger, armored invasion from the North commenced during the Easter Offensive following US ground-forces withdrawal, and had nearly overrun some major southern cities until being beaten back.

Between Tonkin in the north and Cochinchina in the south was the protectorate (xứ bảo hộ) of Annam (Trung Kỳ), under a French resident superior (khâm sứ).

– discuss] the circumstances prevailing in 1955 and 1956 as "anarchy among sects and of the retiring Việt Minh in the South, the 1956 campaign of terror from Hanoi's land reform and resultant peasant uprising around Vinh in the North".

In spite of this, a 1961 US intelligence estimate reported that "one-half of the entire rural region south and southwest of Saigon, as well as some areas to the north, are under considerable Communist control.

"[20] The report, later excerpted in The Pentagon Papers, continued: The Diệm government lost support among the populace, and from the Kennedy administration, due to its repression of Buddhists and military defeats by the Việt Cộng.

Meanwhile, the Gulf of Tonkin incident of 2 August 1964 led to a dramatic increase in direct American participation in the war, with nearly 200,000 troops deployed by the end of the year.

Khánh sought to capitalize on the crisis with the Vũng Tàu Charter, a new constitution that would have curtailed civil liberties and concentrated his power, but was forced to back down in the face of widespread protests and strikes.

On 31 January 1968, the People's Army of Vietnam (PAVN) and the Việt Cộng broke the traditional truce accompanying the Tết (Lunar New Year) holiday.

The new administration of Richard Nixon introduced a policy of Vietnamization to reduce US combat involvement and began negotiations with the North Vietnamese to end the war.

As Saigon began to roll back the Việt Cộng, they found it necessary to adopt a new strategy, hammered out at a series of meetings in Hanoi in March 1973, according to the memoirs of Trần Văn Trà.

After two clashes that left 55 South Vietnamese soldiers dead, President Thiệu announced on 4 January 1974 that the war had restarted and that the Paris Peace Accord was no longer in effect.

In August 1974, Nixon was forced to resign as a result of the Watergate scandal, and the US Congress voted to reduce assistance to South Vietnam from $1 billion a year to $700 million.

In December 1974, the PAVN launched an invasion at Phuoc Long to test the South Vietnamese combat strength and political will and whether the US would respond militarily.

As a consequence, Thiệu ordered a withdrawal of key army units from the Central Highlands, which exacerbated an already perilous military situation and undermined the confidence of the ARVN soldiers in their leadership.

[24] During the hours leading up to the surrender, the United States undertook a massive evacuation of US government personnel as well as high-ranking members of the ARVN and other South Vietnamese who were seen as potential targets for persecution by the Communists.

With the support of the United States government and the CIA, ARVN officers led by General Dương Văn Minh staged a coup and killed him in 1963.

Until late 1965, multiple coups and changes of government occurred, with some civilians being allowed to give a semblance of civil rule overseen by a military junta.

Military rule initially failed to provide much stability however, as internal conflicts and political inexperience caused various factions of the army to launch coups and counter-coups against one another, making leadership very tumultuous.

[26]: 273 In June 1965, Kỳ's influence over the ruling military government was solidified when he forced civilian prime minister Phan Huy Quát from power.

The National Assembly/House of Representatives was located in the Saigon Opera House, now the Municipal Theatre, Ho Chi Minh City,[27]: 100  while the Senate was located at 45-47 Bến Chương Dương Street (đường Bến Chương Dương), District 1, originally the Chamber of Commerce, and now the Ho Chi Minh City Stock Exchange.

[35] U.S. President Dwight D. Eisenhower wrote in 1954 that "I have never talked or corresponded with a person knowledgeable in Indochinese affairs who did not agree that had elections been held as of the time of the fighting, possibly eighty percent of the population would have voted for the Communist Ho Chi Minh as their leader rather than Chief of State Bảo Đại.

"[36] According to the Pentagon Papers, however, from 1954 to 1956 "Ngô Đình Diệm really did accomplish miracles" in South Vietnam:[37] "It is almost certain that by 1956 the proportion which might have voted for Ho—in a free election against Diệm—would have been much smaller than eighty percent.

"[38] In 1957, independent observers from India, Poland, and Canada representing the ICC stated that fair, unbiased elections were not possible, reporting that neither South nor North Vietnam had honored the armistice agreement.

After promising not to do so during the 1964 election campaign, in 1965 President Lyndon B. Johnson decided to send in much larger numbers of combat troops, and conflict steadily escalated to become what is commonly known as the Vietnam War.

The Republic of Vietnam Military Forces (RVNMF; Vietnamese: Quân lực Việt Nam Cộng hòa – QLVNCH), was formally established on 30 December 1955.

[42] Created out from ex-French Union Army colonial Indochinese auxiliary units (French: Supplétifs), gathered earlier in July 1951 into the French-led Vietnamese National Army – VNA (Vietnamese: Quân Đội Quốc Gia Việt Nam – QĐQGVN), Armée Nationale Vietnamiènne (ANV) in French, the armed forces of the new state consisted in the mid-1950s of ground, air, and naval branches of service, respectively: Their roles were defined as follows: to protect the sovereignty of the free Vietnamese nation and that of the Republic; to maintain the political and social order and the rule of law by providing internal security; to defend the newly independent Republic of Vietnam from external (and internal) threats; and ultimately, to help reunify Vietnam.

The impact of the 1973 oil crisis, a faltering economy, inflation and reduced US aid led to a steady decline in South Vietnamese military expenditure and effectiveness.