On 1 November 1963, Ng nh Dim, the president of South Vietnam, was arrested and assassinated in a successful coup d'tat led by General Dng Vn Minh. The coup was the culmination of nine years of autocratic and nepotistic family rule in the country. Discontent with the Dim regime had been simmering below the surface and exploded with mass Buddhist protests against longstanding religious discrimination after the government shooting of protesters who defied a ban on the flying of the Buddhist flag.

The Army of the Republic of Vietnam (ARVN) had launched a bloody overnight siege on Gia Long Palace in Saigon. When rebel forces entered the palace, Dim and his adviser and younger brother Ng nh Nhu were not present, having escaped before to a loyalist shelter in Cholon. The brothers had kept in communication with the rebels through a direct link from the shelter to the palace, and misled them into believing that they were still in the palace. The Ng brothers soon agreed to surrender and were promised safe exile; after being arrested, they were instead executed in the back of an armoured personnel carrier by ARVN officers on the journey back to military headquarters near Tn Sn Nht Air Base. While no formal inquiry was conducted, the responsibility for the deaths of the Ng brothers is commonly placed on Minh's bodyguard, Captain Nguyn Vn Nhung and on Major Dng Hiu Ngha, both of whom guarded the brothers during the trip. Minh's army colleagues and US officials in Saigon agreed that Minh ordered the executions. They postulated various motives, including that the brothers had embarrassed Minh by fleeing the Gia Long Palace, and that the brothers were killed to prevent a later political comeback. The generals initially attempted to cover up the execution by suggesting that the brothers had committed suicide, but this was contradicted when photos of the Ngs' corpses surfaced in the media.

South Vietnam, officially the Republic of Vietnam (RVN; Vietnamese: Việt Nam Cộng Hòa; French: République du Viêt Nam), was a country that existed from 1955 to 1975, the period when the southern portion of Vietnam was a member of the Western Bloc during part of the Cold War. It first received international recognition in 1949 as the State of Vietnam within the French Union, with its capital at Saigon (renamed to Ho Chi Minh City in 1976), before becoming a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957.The end of the Second World War saw anti-Japanese Việt Minh guerrilla forces, led by communist fighter Ho Chi Minh, proclaiming the establishment of the Democratic Republic of Vietnam in Hanoi in September 1945. In 1949, anti-communist politicians formed a rival government in Saigon led by former emperor Bảo Đại. A 1955 referendum on the state's future form of government was highly contested 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. After the 1954 Geneva Conference, it abandoned its claims to the northern part of the country and established its sovereignty over the southern half of Vietnam consisting of Cochinchina (Nam Kỳ) – a former French colony and parts of Annam (Trung Kỳ) – a former French protectorate. Diệm was killed in a military coup led by general Dương Văn Minh with help from the CIA in 1963, and a series of short-lived military governments followed. General Nguyễn Văn Thiệu then led the country after a US-encouraged civilian presidential election from 1967 until 1975.

The beginnings of the Vietnam War occurred in 1955 with an uprising by the newly organized National Liberation Front for South Vietnam (Việt Cộng), armed and supported by the North Vietnam, with backing mainly from China and the Soviet Union. Larger escalation of the insurgency occurred in 1965 with American intervention and the introduction of regular forces of Marines, followed by Army units to supplement the cadre of military advisors guiding the Southern armed forces. 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. Fighting peaked up to that point during the Tet Offensive of February 1968, when there were over a million South Vietnamese soldiers and 500,000 US soldiers in South Vietnam. What started as a guerrilla war eventually turned into a more conventional fight as the balance of power became equalized. An even larger, armored invasion from the North commenced during the Easter Offensive following US ground-forces withdrawal, and had nearly overran some major northern cities until beaten back.

Despite a truce agreement under the Paris Peace Accords, concluded in January 1973 after five years of on-and-off negotiations, fighting continued almost immediately afterwards. The regular North Vietnamese army and Việt-Cộng auxiliaries launched a major second combined-arms conventional invasion in 1975. Communist forces overran Saigon on 30 April 1975, marking the end of the Republic of Vietnam. On 2 July 1976, North Vietnam-controlled Provisional Revolutionary Government of the Republic of South Vietnam and the Democratic Republic of Vietnam (North Vietnam) merged to form the Socialist Republic of Vietnam.