The Vietnam War (1945–1975)

by: History SparkNotes

Key Terms

terms Key Terms


17th Parallel

The dividing line between North Vietnam and South Vietnam as established by the 1954Geneva Conference. The 17th parallel was buffered by a demilitarized zone, or DMZ, between the two countries.

Agent Orange

A chemical herbicide and defoliant that U.S. forces sprayed extensively in order to kill vegetation in the Vietnamese jungle and expose Viet Cong hideouts. Agent Orange inflicted immense damage on Vietnam’s natural environment and led to decades of unforeseen health problems among Vietnamese civilians and U.S. military forces.


The central of the three divisions of French colonial Vietnam, between Tonkin to the north and Cochin China to the south. The major city in Annam was Hue.

Army of the Republic of Vietnam (ARVN)

The national army of South Vietnam, which U.S. “military advisors” of the MACV trained beginning in 1962. By 1965, after several defeats by the Viet Cong at battles such as Ap Bac and Pleiku, the ARVN was seen as ineffective.

Binh Xuyen

The Vietnamese mafia, headquartered in a Chinese-dominated Saigon suburb of Cholon. The Binh Xuyen influenced politics in southern Vietnam under the corrupt French-backed government.

Can Lao

The South Vietnamese secret police during the Ngo Dien Diem regime, which was controlled by Diem’s hated brother Ngo Dinh Nhu.

Cao Dai

An eclectic cult in South Vietnam that combined elements of Eastern religions and Western history and culture. The Cao Dai exerted considerable influence on the corrupt French-backed government in southern Vietnam in the late 1940s.

Central Office of South Vietnam (COSVN)

The alleged central command center that controlled all Viet Cong operations during the Vietnam War. Although U.S. military officials insisted that the COSVN existed, it was never found, despite exhaustive, resource-draining search campaigns by U.S. forces. It is unclear whether the COSVN ever existed at all, as the Viet Cong was notorious for decentralized guerrilla operations that were difficult to pin down or disable.

Christmas Bombing

An intensive bombing campaign against Hanoi that President Richard M. Nixon launched in late December 1972, in an attempt to force the North Vietnamese into a peace settlement. The NVA did not surrender but instead called for a cease-fire, which was signed in January 1973.

Cochin China

The southernmost of the three divisions of French colonial Vietnam, below Tonkin and Amman to the north. The major city in Cochin China was Saigon.


The FBI’s counterintelligence program, which President Lyndon B. Johnson authorized to spy on domestic anti–Vietnam War activists toward the end of his administration. COINTELPRO agents planted false evidence and arrested hundreds of antiwar activists on bogus charges of supporting Communism. These harsh and illegal tactics turned the American public away from the federal government and widened the credibility gap.


A U.S. foreign policy strategy during the Cold War, developed in 1947 by State Department analyst George F. Kennan. Under containment, the United States would not challenge nations already in the Soviet Union’s sphere of influence but also would not tolerate any further Soviet or Communist expansion. Although containment was meant to apply primarily to Europe, it evolved into the domino theory that formed the basis for U.S. involvement in Vietnam.

Credibility Gap

The term applied to the difference between what the U.S. military and Lyndon B. Johnson were telling the American public about the Vietnam War and what the American media said was actually occurring on the ground. As a result of the credibility gap, many Americans began to question the president’s honesty. This “credibility gap” widened further when Johnson authorized both the CIA and FBI’s COINTELPRO to spy on antiwar activists. The credibility gap made Johnson a political liability for the Democratic Party, and he declined to run for reelection in 1968.

Demilitarized Zone (DMZ)

The no-man’s-land surrounding the border between NorthVietnam and South Vietnam at the 17th parallel.

Democratic Republic of Vietnam (DRV)

The Ho Chi Minh-led Communist government of North Vietnam which was created after the 1954 Geneva Conference divided the country at the 17th parallel.

Dien Bien Phu

A small village in the remote, mountainous northwest corner of Vietnam that was the site of a major French defeat at the hands of the Viet Minh in 1954. The French attempted to lure the Viet Minh into a trap at Dien Bien Phu, where a central base with an airstrip was defended by three surrounding artillery bases. Viet Minh General Vo Nguyen Giap, however, had Vietnamese peasants smuggle disassembled artillery pieces into the surrounding mountains, where they were then reassembled and used to bombard the French airstrip, destroying the French supply line. The decisive battle of the First Indochina War, Dien Bien Phu led France to seek a peace settlement and gave the Viet Minh negotiating power at the Geneva Conference.

Domino Theory

First popularized by President Dwight D. Eisenhower in 1954, the idea that if one nation fell to Communism, the surrounding nations would be likely to fall to Communism as well, starting a chain reaction in which nations fell like dominoes in a line. The domino theory guided U.S. foreign policy for years and was used to justify U.S. involvement in Vietnam.


A practice, which erupted sporadically late in the Vietnam War, in which demoralized U.S. servicemen killed their own superior officers in order to avoid being sent on dangerous missions. Although fragging was not widespread, numerous specific incidents were reported.

French Indochina

The French colonial term for the area encompassing present-day Cambodia, Laos, and Vietnam (which was itself composed of Tonkin, Annam, and Cochin China).

Geneva Conference

A 1954 peace conference at the end of the First Indochina War, prompted by the stunning French defeat at Dien Bien Phu. The conference issued the Geneva Accords, which divided Vietnam officially into North Vietnam and South Vietnam along the 17th parallel as a temporary measure and promised free Vietnam-wide elections for 1956 (although these elections never occurred).

Gulf of Tonkin Resolution

A 1964 resolution, passed by a near-unanimous vote in the U.S. Congress, that gave President Lyndon B. Johnson a free hand to escalate the war in Vietnam. The resolution was prompted by an incident in which two U.S. Navy destroyers were allegedly attacked by North Vietnamese forces in the Gulf of Tonkin. Though not an explicit war declaration, the resolution empowered Johnson to initiate Operation Rolling Thunder and allowed a process of escalation that would eventually see more than 500,000 U.S. soldiers committed to the war in Vietnam.

Hao Hoa

An organization in southern Vietnam that combined Buddhism and nationalism and openly opposed the French colonial government. The Hao Hoa built a sizable army and in the 1950s counted over a million people as members.

Military Assistance Command of Vietnam (MACV)

A group of U.S. “military advisors” whom President John F. Kennedy sent to Vietnam in 1962 to train the South Vietnamese army, the ARVN, to fight against the Viet Cong. The MACV’s numbers soared steadily through the 1960s as the United States became increasingly involved in Vietnam. General William C. Westmoreland became head of MACV in 1964.

My Lai Massacre

A 1968 raid on the tiny village of My Lai by an American unit in South Vietnam. The soldiers, angry and frustrated at their inability to find Viet Cong operatives in the village, killed up to 500 unarmed Vietnamese civilians—men, women, children, and elderly—without provocation. News of the massacre surfaced in 1969, outraging Americans and turning public opinion against the U.S. military. The leader of the company, Lieutenant William Calley, was court-martialed in 1971 and sentenced to a life term but later paroled.


A flammable, sprayable, gasoline-based gel that the U.S. military used extensively as a weapon in Vietnam. Napalm inflicted devastating burns, killing and maiming many Vietnamese soldiers and civilians.

National Liberation Front (NLF)

An organization formed in 1960 to provide structure and support to the formerly isolated cells of the southern Viet Cong. Eventually, the terms NLF and Viet Cong came to be used interchangeably.

Nixon Doctrine

A proclamation issued by President Richard M. Nixon in 1969 that the United States would no longer send troops to fight Communist revolutions abroad. The doctrine, issued along with his policy of Vietnamization, effectively reversed the policies of several post–World War II U.S. presidents.


A 1950 National Security Council memo that advocated an enormous increase in U.S. military spending to combat the perceived growing threat of Communism. NSC-68 contributed to the domino theory that was later used to justify U.S. involvement in Vietnam.

Operation Rolling Thunder

A sustained U.S. bombing effort against North Vietnam authorized by President Lyndon B. Johnson in 1965 and lasting until 1968. Rolling Thunder was launched in response to a Viet Cong raid on a U.S. military base at Pleiku that killed several U.S. servicemen. When the air strikes failed to end the war, Johnson increased the number of U.S. soldiers in South Vietnam from roughly 200,000 to over 500,000.

Pentagon Papers

A secret U.S. government report originally commissioned by Secretary of State Robert S. McNamara to detail U.S. involvement in Vietnam since World War II. In 1971, the Pentagon Papers were leaked to the New York Times and other newspapers and caused an uproar. When the Nixon administration attempted to block their publication, the U.S. Supreme Court issued a ruling to allow their release to continue. Because the Pentagon Papers revealed that the U.S. government had lied about numerous secret operations in Vietnam, the American public grew even more distrustful of the government.

Republic of Vietnam (RVN)

The corrupt, U.S.-backed government of South Vietnam, which Ngo Dinh Diem proclaimed in 1955.

Search and Destroy

A U.S. military strategy designed to send U.S. troops out into the field proactively to locate and kill Viet Cong forces. The policy, instituted and supported by General William C. Westmoreland, stood in contrast to the previous U.S. policy to protect only “strategic enclaves, those areas that the South Vietnamese government still held.

Silent Majority

The key words in a statement by President Richard M. Nixon about the antiwar movement. Nixon claimed that despite the fact that antiwar protests were becoming vocal and widespread, a “silent majority” of Americans still supported the war in Vietnam. In other words, the president claimed that noisy activists constituted only a small percentage of the American public.

Students for a Democratic Society (SDS)

One of the major organizations of antiwar protesters in the United States during the 1960s. Founded in 1959, the quasi-socialist SDS began to organize widespread protests against the U.S. military draft by 1965.

Tet Offensive

A massive offensive launched by Viet Cong guerrillas on January 30, 1968, the Vietnamese new year holiday of Tet. The Tet Offensive comprised simultaneous attacks on dozens of U.S.-controlled sites in South Vietnam. Although the offensive resulted in a tactical victory for the United States and many Viet Cong casualties, the American public saw it as a setback, as the U.S. military and President Lyndon B. Johnson had led them to believe that the Viet Cong was already well on its way to defeat. The Tet Offensive caused public support for the war to plummet in the United States, especially when the U.S. military requested 200,000 soldiers in the months following the attacks.


The northernmost of the three divisions of French colonial Vietnam, above Amman and Cochin China to the south. The major city in Tonkin was Hanoi.

Twenty-Sixth Amendment

A 1971 amendment to the U.S. Constitution that lowered the voting age from twenty-one to eighteen. The amendment was passed in response to protests that young U.S. soldiers fighting and dying in Vietnam lacked the legal right to vote for or against the politicians who were running the war. Although antiwar activists welcomed the amendment, they continued to protest.

Viet Cong (VC)

Akin to the American slang word “Commies,” an originally mildly derisive term for Communist forces in South Vietnam who opposed the U.S.-backed government in Saigon. “Viet Cong” grew to lose its negative connotation and came into common use as the war progressed. By the time of U.S. involvement, the Viet Cong was a sizable guerrilla force hidden among South Vietnam’s population, making its members extremely difficult to find or target. It often worked in conjunction with the professional North Vietnamese Army(NVA) to attack U.S. soldiers and supply lines. The United States lost the war in Vietnam in large part due to the Viet Cong’s tenacity and its widespread popularity with the South Vietnamese.

Viet Minh

Vietnamese Communist resistance forces, based in northern Vietnam and led by Ho Chi Minh, during the First Indochina War with France (19451954).


President Richard M. Nixon’s 1969 plan that called for withdrawing almost all of the 500,000 U.S. troops in Vietnam over the next year and handing over more responsibility to the South Vietnamese. Although Nixon did remove troops, he also planned another intensive round of bombing in North Vietnam to convince Hanoi to end the war.

War Powers Resolution

An act passed by the U.S. Congress in 1973 after the extent of President Richard M. Nixon’s secret bombing campaigns in neutral Cambodia was revealed. The act required the president to notify Congress upon launching any U.S. military action abroad and limited any such action to sixty to ninety days in duration if Congress did not approve it.


A domestic scandal in the United States that began in the summer of 1972, when police arrested five men breaking into the Democratic Party headquarters at the Watergate Hotel in Washington, D.C. President Richard M. Nixon publicly denied having any prior knowledge of the incident and created a special investigative committee to look into the matter. Eventually, it was revealed that Nixon had authorized both the break-in and the cover-up that followed. As the scandal exploded, calls arose for Nixon’s impeachment; Nixon ultimately resigned in 1974. Taking advantage of the confusion and distraction in the Nixon administration, North Vietnamese forces moved into South Vietnam, setting the stage for an offensive in the spring of 1975 that led to the fall of Saigon.

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