1963 South Vietnamese coup d'état in the context of "U.S. involvement in the Vietnam War"

The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam was supported by the Soviet Union and China, while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina wars and a proxy war of the Cold War between the Soviet Union and US. The Vietnam War was one of the postcolonial wars of national liberation, a theater in the Cold War, and a civil war, with civil warfare a defining feature from the outset. Direct US military involvement escalated from 1965 until its withdrawal in 1973. The fighting spilled into the Laotian and Cambodian Civil Wars, which ended with all three countries becoming communist in 1975.

After the defeat of the French Union in the First Indochina War that began in 1946, Vietnam gained independence in the 1954 Geneva Conference but was divided in two at the 17th parallel: the Viet Minh, led by Ho Chi Minh, took control of North Vietnam, while the US assumed financial and military support for South Vietnam, led by Ngo Dinh Diem. The North Vietnamese supplied and directed the Viet Cong (VC), a common front of dissidents in the south which intensified a guerrilla war from 1957. In 1958, North Vietnam invaded Laos, establishing the Ho Chi Minh trail to supply the VC. By 1963, the north had covertly sent 40,000 soldiers of its People's Army of Vietnam (PAVN), armed with Soviet and Chinese weapons, to fight in the insurgency in the south. President John F. Kennedy increased US involvement from 900 military advisors in 1960 to 16,000 in 1963 and sent more aid to the Army of the Republic of Vietnam (ARVN), which failed to produce results. In 1963, Diem was killed in a US-backed military coup, which added to the south's instability.

The involvement of the United States in the Vietnam War began in the 1950s and greatly escalated in 1965 until its withdrawal in 1973. The U.S. military presence in Vietnam peaked in April 1969, with 543,000 military personnel stationed in the country. By the end of the U.S. involvement, more than 3.1 million Americans had been stationed in Vietnam, and 58,279 had been killed.

After World War II ended in 1945, President Harry S. Truman declared his doctrine of "containment" of communism in 1947 at the start of the Cold War. U.S. involvement in Vietnam began in 1950, with Truman sending military advisors to assist the French Union against Viet Minh rebels in the First Indochina War. The French withdrew in 1954, leaving North Vietnam in control of the country's northern half. President Dwight D. Eisenhower ordered covert CIA activities in South Vietnam. Opposition to the regime of Ngo Dinh Diem in South Vietnam was quashed with U.S. help, but from 1957 insurgents known as the Viet Cong launched a campaign against the state. North Vietnam supported the Viet Cong, which began fighting the South Vietnamese army. President John F. Kennedy, who subscribed to the "domino theory" that communism would spread to other countries if Vietnam fell, expanded U.S. aid to South Vietnam, increasing the number of advisors from 900 to 16,300, but this failed to produce results. In 1963, Diem was deposed and killed in a military coup tacitly approved by the U.S. North Vietnam began sending detachments of its own army, armed with Soviet and Chinese weapons, to assist the Viet Cong.

Ngô Đình Diệm (/djɛm/ dyem, /ˈjiːəm/ YEE-əm or /ziːm/ zeem; Vietnamese: [ŋō ɗìn jîəmˀ] ; 3 January 1901 – 2 November 1963) was a South Vietnamese politician who was the final prime minister of the State of Vietnam (1954–1955) and later the first president of South Vietnam (Republic of Vietnam) from 1955 until his capture and assassination during the CIA-backed 1963 coup d'état.

Diệm was born into a prominent Catholic family with his father, Ngô Đình Khả, being a high-ranking mandarin for Emperor Thành Thái during the French colonial era. Diệm was educated at French-speaking schools and considered following his brother Ngô Đình Thục into the priesthood, but eventually chose to pursue a career in the civil service. He progressed rapidly in the court of Emperor Bảo Đại, becoming governor of Bình Thuận Province in 1929 and interior minister in 1933. However, he resigned from the latter position after three months and publicly denounced the emperor as a tool of France. Diệm came to support Vietnamese nationalism, promoting both anti-communism, in opposition to Ho Chi Minh, and decolonization, in opposition to Bảo Đại. He established the Cần Lao Party to support his political doctrine of Person Dignity Theory, which was a blend of the philosophies of Personalism, especially as understood by French philosopher Emmanuel Mounier, and of Confucianism, which Diệm and his father had greatly admired. Diệm supported the Confucian concept of "Mandate of Heaven", and wished to make it the basis of political theory that would emerge in Vietnam.

Dương Văn Minh (Vietnamese: [jɨəŋ van miŋ̟] or [zɨəŋ van miŋ̟]; 16 February 1916 – 6 August 2001), popularly known as Big Minh, was a South Vietnamese politician and a senior general in the Army of the Republic of Vietnam (ARVN) and a politician during the presidency of Ngô Đình Diệm. In 1963, he became chief of a military junta after leading a coup in which Diệm was assassinated. Minh lasted only three months before being toppled by Nguyễn Khánh, but assumed power again as the fourth and last President of South Vietnam in April 1975, two days before surrendering to North Vietnamese forces. He earned his nickname "Big Minh", because he was approximately 1.83 m (6 ft) tall and weighed 90 kg (198 lb).

Born in Tiền Giang province in the Mekong Delta region of southern Vietnam, Minh joined the French Army at the start of World War II, and was captured and tortured by the Imperial Japanese, who invaded and seized French Indochina. After his release, he joined the French-backed Vietnamese National Army (VNA) and was imprisoned by the communist-dominated Viet Minh before breaking out. In 1955, after Vietnam was partitioned and the State of Vietnam controlled the southern half under Prime Minister Ngô Đình Diệm, Minh led the VNA in decisively defeating the Bình Xuyên paramilitary crime syndicate in street combat and dismantling the Hòa Hảo religious tradition's private army. This made him popular with the people and Diệm, but the latter later put him in a powerless position, regarding him as a threat.