August 15, 1945 — Japan surrenders to the Allies. In Indochina, the Japanese administration allows Hồ Chí Minh to take over control of the country. This is called the August Revolution. Hồ Chí Minh fights with a variety of other political factions for control of the major cities.

August 1945 — A few days after the Vietnamese "revolution", Nationalist Chinese forces enter from the north and, as previously planned by the allies, establish an administration in the country as far south as the 16th parallel north.

September 26, 1945: Office of Strategic Services (OSS) officer Lieutenant Colonel A. Peter Dewey — working with the Viet Minh to repatriate Americans captured by the Japanese — is mistaken for a Frenchman, shot and killed by the Viet Minh. He thus became the first American casualty in Vietnam. (Not precisely accurate. Prior to 1950 the area later recognized as Viet Nam was known as French Indochina. Thus, LTC Dewey was the first American casualty in French Indochina).

October 1945 — British troops land in southern Vietnam and establish a provisional administration. The British free French soldiers and officials imprisoned by the Japanese. The French begin taking control of cities within the British zone of occupation.

February 1946 — The French sign an agreement with China. France gives up its concessions in Shanghai and other Chinese ports. In exchange, China agrees to assist the French in returning to Vietnam north of the 17th parallel.

March 6, 1946 — After negotiations with the Chinese and the Viet Minh, the French sign an agreement recognizing Vietnam within the French Union. Shortly after, the French land at Haiphong and occupy the rest of northern Vietnam. The Viet Minh use the negotiating process with France and China to buy time to use their armed forces to destroy all competing nationalist groups in the north.

December 1946 — Negotiations between the Viet Minh and the French break down. The Viet Minh are driven out of Hanoi into the countryside.

1949 — Chinese communists reach the northern border of Indochina. The Viet Minh drive the French from the border region and begin to receive large amounts of weapons from the Soviet Union and China. The weapons transform the Viet Minh from an irregular large-scale insurgency into a conventional army.

May 1, 1950 — After the capture of Hainan Island from Chinese Nationalist forces by the Chinese People's Liberation Army, President Truman approves $10 million in military assistance for anti-communist efforts in Indochina. The Defense Attaché Office was established in Saigon in May 1950, a formal recognition of Viet Nam (vice French IndoChina). This was the beginning of formal US military personnel assignments in Viet Nam. US Naval, Army and Air Force personnel established their respective attaches at this time.

September 1950 - Truman sends the Military Assistance Advisory Group (MAAG) Indochina to Vietnam to assist the French. The President claimed they were not sent as combat troops, but to supervise the use of $10 million worth of US military equipment to support the French in their effort to fight the Viet Minh forces.

Following the outbreak of the Korean War, Truman announces "acceleration in the furnishing of military assistance to the forces of France and the Associated States in Indochina..." and sends 123 non-combat troops to help with supplies to fight against the communist Viet Minh.

1954 — In January, Navarre's Deputy asked for additional transport aircraft. Negotiations ended on March 3 with 24 CIA pilots (CAT) to operate 12 US Air Force C-119s, flying undercover using French insignia, but maintained by the USAF.[3]

1954 — The Viet Minh defeat the French at the battle of Dien Bien Phu. The defeat, along with the end of the Korean War the previous year, causes the French to seek a negotiated settlement to the war.

1954 — The Geneva Conference (1954), called to determine the post-French future of Indochina, proposes a temporary division of Vietnam, to be followed by nationwide elections to unify the country in 1956.

1955 — North Vietnam launches an 'anti-landlord' campaign, during which counter-revolutionaries are imprisoned or killed. The numbers killed or imprisoned are disputed, with historian Stanley Karnow estimating about 6,000 while others (see the book "Fire in the Lake") estimate only 800. R.J. Rummel puts the figure as high as 200,000.[4]

June 1961 — Kennedy meets with Khrushchev in Vienna. He protests North Vietnam's attacks on Laos and points out that the U.S. was supporting the neutrality of Laos. The two leaders agree to pursue a policy of creating a neutral Laos.

June 1961 — Kennedy said, "Now we have a problem making our power credible and Vietnam looks like the place" to James Reston of The New York Times (immediately after meeting Khrushchev in Vienna).

May 8, 1963 — Buddhists demonstrate in Huế, South Vietnam after the display of religious flags were prohibited, during the celebration of Vesak, Gautama Buddha's birthday; but, Catholic flags celebrating the consecration of Archbishop Ngô Đình Thục, brother of Ngô Đình Diệm were not prohibited. The police of Ngô Đình Cẩn, Diệm's younger brother, open fire, killing nine.

May 1963 — Republican Barry Goldwater declares that the U.S. should fight to win or withdraw from Vietnam. Later on, during his presidential campaign against Lyndon B. Johnson, his Democratic opponents accuse him of wanting to use nuclear weapons in the conflict.

June 11, 1963 — Photographs of protesting Buddhist monk, Thích Quảng Đức, burning himself to death in protest, in Saigon, appear in U.S. newspapers.

Summer 1963 — Madame Nhu, de facto First Lady to the bachelor Diệm makes a series of vitriolic attacks on Buddhists, calling the immolations "barbecues". Diệm ignores US calls to silence her.

August 21, 1963 — ARVN special forces loyal to Ngô Đình Nhu, younger brother of Diệm, stage raids across the country, attacking Buddhist temples and firing on monks. The cremated remains of Thích Quảng Đức are confiscated from Xá Lợi Pagoda in Saigon. New US ambassador Henry Cabot Lodge rebukes Diệm by visiting Xá Lợi and giving refuge to Buddhist leader Thích Trí Quang. The US calls for Nhu to be dropped by Diệm, and threatens to cut aid to Colonel Lê Quang Tung's Special Forces if they are not sent into battle, rather than used to repress dissidents.

September 2, 1963 — Kennedy criticises the Diệm regime in an interview with Walter Cronkite, citing the Buddhist repression and claiming that Diệm is out of touch.

Late October 1963 — Nhu, unaware that Saigon region commander General Tôn Thất Đính is double-crossing him, draws up plans for a phony coup and counter-coup to reaffirm the Diệm regime. Đính sends Nhu's loyal special forces out of Saigon on the pretext of fighting communists and in readiness for the counter coup, and rings Saigon with rebel troops.

November 1, 1963 — Military officers launch a coup d'état against Diệm, with the tacit approval of the Kennedy administration. Diệm and Nhu escape the presidential residence via a secret exit after loyalist forces were locked out of Saigon, unable to rescue them.

November 2, 1963 — Diệm and Nhu are discovered in nearby Cholon. Although they had been promised exile by the junta, they are executed by Nguyễn Văn Nhung, bodyguard of General Dương Văn Minh. Minh leads the military junta.

November 1963 — By this time, Kennedy had increased the number of military personnel from the 900 that were there when he became President to 16,000 just before his death.[7]

In 1961 the new administration of President John F. Kennedy remained essentially committed to the bi-partisan, anti-communist foreign policies inherited from the administrations of Presidents Truman and Eisenhower. During 1961, his first year in office, Kennedy found himself faced with a three-part crisis: The failure of the Bay of Pigs invasion in Cuba; the construction of the Berlin Wall by the Soviets; and a negotiated settlement between the pro-Western government of Laos and the Pathet Lao communist movement. Fearing that another failure on the part of the U.S. to stop communist expansion would fatally damage U.S. credibility with its allies, Kennedy realized, "Now we have a problem in making our power credible... and Vietnam looks like the place."[8] The commitment to defend South Vietnam was reaffirmed by Kennedy on May 11 in National Security Action Memorandum 52, which became known as "The Presidential Program for Vietnam". Its opening statement reads:

U.S. objectives and concept of operations [are] to prevent communist domination of South Vietnam; to create in that country a viable and increasingly democratic society, and to initiate, on an accelerated basis, a series of mutually supporting actions of a military, political, economic, psychological, and covert character designed to achieve this objective.[9]

Kennedy was intrigued by the idea of utilizing United States Army Special Forces for counterinsurgency conflicts in Third World countries threatened by the new "wars of national liberation". Originally intended for use behind front lines after a conventional invasion of Europe, Kennedy believed that the guerrilla tactics employed by Special Forces would be effective in the "brush fire" war in South Vietnam. He saw British success in using such forces during the Malayan Emergency as a strategic template. Thus in May 1961 Kennedy sent detachments of Green Berets to South Vietnam to train South Vietnamese soldiers in guerrilla warfare.

The Diệm regime had been initially able to cope with the insurgency of the National Front for the Liberation of South Vietnam (NLF, or derogatively, Viet Cong) in South Vietnam with the aid of U.S. matériel and advisers, and, by 1962, seemed to be gaining the upper hand. Senior U.S. military leaders received positive reports from the U.S. commander, General Paul D. Harkins of the Military Assistance Command, Vietnam, or MACV. By the following year, however, cracks began to appear in the façade of success. In January a possible victory that was turned into a stunning defeat for government forces at the Battle of Ap Bac caused consternation among both the military advisers in the field and among politicians in Washington, D.C. JFK also indicated to Walter Cronkite that the war may be unwinnable, and that it was ultimately a Vietnamese war, not an American war.[10]

Diệm was already growing unpopular with many of his countrymen because of his administration's nepotism, corruption, and its apparent bias in favor of the Catholic minority—of which Diệm was a part—at the expense of the Buddhist majority. This contributed to the impression of Diệm's rule as an extension of the French Colonial regime. Promised land reforms were not instituted, and Diệm's strategic hamlet program for village self-defense (and government control) was a disaster. The Kennedy administration grew increasingly frustrated with Diệm. In 1963, a crackdown by Diệm's forces was launched against Buddhist monks protesting discriminatory practices and demanding a political voice. Diệm's repression of the protests sparked the so-called Buddhist Revolt, during which several monks committed self-immolation, which was covered in the world press. The communists took full advantage of the situation and fueled anti-Diệm sentiment to create further instability.

Commandant of the Marine Corps Wallace Greene (left), III MAF commander General Robert Cushman (center), and General Westmoreland (right).

On July 27, 1964, 5,000 additional U.S. military advisers were ordered to the Republic of Vietnam (RVN or South Vietnam), bringing the total American troop level to 21,000. Shortly thereafter an incident occurred off the coast of the Democratic Republic of Vietnam (North Vietnam) that was destined to escalate the conflict to new levels and lead to the full scale Americanization of the war.

On the evening of August 2, 1964, the destroyerUSS Maddox was conducting an electronic intelligence collection mission in international waters (even as claimed by North Vietnam) in the Gulf of Tonkin when it was attacked by three P-4 torpedo boats of the North Vietnamese Navy.[11] Reports later reached the Johnson administration saying that the Maddox was under attack. Two nights later, after being joined by the destroyer C. Turner Joy, the Maddox again reported that both vessels were under attack (this event, which took place under adverse weather conditions, in fact never occurred).[citation needed] Regardless, President Johnson addressed Congress asking for more political power to utilize American military forces in South Vietnam, using the attack on the Maddox as cause to get what he wanted.

There was rampant confusion in Washington, but the incident was seen by the administration as the perfect opportunity to present Congress with "a pre-dated declaration of war" in order to strengthen weakening morale in South Vietnam through reprisal attacks by the U.S. on the North.[12] Even before confirmation of the phantom attack had been received in Washington, President Johnson had decided that an attack could not go unanswered.

Just before midnight he appeared on television and announced that retaliatory air strikes were underway against North Vietnamese naval and port facilities. Neither Congress nor the American people learned the whole story about the events in the Gulf of Tonkin until the publication of the Pentagon Papers in 1969. It was on the basis of the administration's assertions that the attacks were "unprovoked aggression" on the part of North Vietnam, that the United States Congress approved the Southeast Asia Resolution (also known as the Gulf of Tonkin Resolution) on August 7. The law gave the President broad powers to conduct military operations without an actual declaration of war. The resolution passed unanimously in the House of Representatives and was opposed in the Senate by only two members.

In February 1965, a U.S. air base at Pleiku, in the Central Highlands of South Vietnam, was attacked twice by the NLF, resulting in the deaths of over a dozen U.S. personnel. These guerrilla attacks prompted the administration to order retaliatory air strikes against North Vietnam.

Operation Rolling Thunder was the code name given to a sustained strategic bombing campaign targeted against the North by aircraft of the U.S. Air Force and Navy that was inaugurated on March 2, 1965. Its original purpose was to bolster the morale of the South Vietnamese and to serve as a signaling device to Hanoi. U.S. airpower would act as a method of "strategic persuasion", deterring the North Vietnamese politically by the fear of continued or increased bombardment. Rolling Thunder gradually escalated in intensity, with aircraft striking only carefully selected targets. When that did not work, its goals were altered to destroying North Vietnam's will to fight by destroying the nation's industrial base, transportation network, and its (continually increasing) air defenses. After more than a million sorties were flown and three-quarters of a million tons of bombs were dropped, Rolling Thunder was ended on November 11, 1968.[13]

President Johnson had already appointed General William C. Westmoreland to succeed General Harkins as Commander of MACV in June 1964. Under Westmoreland, the expansion of American troop strength in South Vietnam took place. American forces rose from 16,000 during 1964 to more than 553,000 by 1969. With the U.S. decision to escalate its involvement, ANZUS Pact allies Australia and New Zealand agreed to contribute troops and matériel to the conflict. They were quickly joined by the Republic of Korea (second only to the Americans in troop strength), Thailand, and the Philippines. The U.S. paid for (through aid dollars) and logistically supplied all of the allied forces.

U.S. aircraft bombs NLF positions in 1965.

Meanwhile, political affairs in Saigon were finally settling down — at least as far as the Americans were concerned. On February 14 the most recent military junta, the National Leadership Committee, installed Air Vice-Marshal Nguyễn Cao Kỳ as prime minister. In 1966, the junta selected General Nguyễn Văn Thiệu to run for president with Ky on the ballot as the vice-presidential candidate in the 1967 election. Thieu and Ky were elected and remained in office for the duration of the war. In the presidential election of 1971, Thieu ran for the presidency unopposed. With the installation of the Thieu and Ky government (the Second Republic), the U.S. had a pliable, stable, and semi-legitimate government in Saigon with which to deal.

With the advent of Rolling Thunder, American airbases and facilities needed to be constructed and manned for the aerial effort. The defense of those bases would not be entrusted to the South Vietnamese. So, on March 8, 1965, 3,500 United States Marines came ashore at Da Nang as the first wave of U.S. combat troops into South Vietnam, adding to the 25,000 U.S. military advisers already in place. On May 5 the U.S. 173rd Airborne Brigade became the first U.S. Army ground unit committed to the conflict in South Vietnam. On August 18, Operation Starlite began as the first major U.S. ground operation, destroying an NLF stronghold in Quảng Ngãi Province. The NLF learned from their defeat and subsequently tried to avoid fighting an American-style ground war by reverting to small-unit guerrilla operations.

The North Vietnamese had already sent units of their regular army into southern Vietnam beginning in late 1964. Some officials in Hanoi had favored an immediate invasion of the South, and a plan was developed to use PAVN units to split southern Vietnam in half through the Central Highlands. The two imported adversaries first faced one another during Operation Silver Bayonet, better known as the Battle of the Ia Drang. During the savage fighting that took place, both sides learned important lessons. The North Vietnamese, who had taken horrendous casualties, began to adapt to the overwhelming American superiority in air mobility, supporting arms, and close air support by moving in as close as possible during confrontations, thereby negating the effects of the above. The Americans learned that PAVN (which was basically a light infantry force) was not a rag-tag band of guerrillas, but was instead a highly disciplined, proficient, and well motivated force.

On November 27, 1965, the Pentagon declared that if the major operations needed to neutralize North Vietnamese and NLF forces were to succeed, U.S. troop levels in South Vietnam would have to be increased from 120,000 to 400,000. In a series of meetings between Westmoreland and the President held in Honolulu in February 1966, Westmoreland argued that the U.S. presence had succeeded in preventing the immediate defeat of the South Vietnamese government but that more troops would be necessary if systematic offensive operations were to be conducted. The issue then became in what manner American forces would be used.

The nature of the American military's strategic and tactical decisions made during this period would color the conduct and nature of the conflict for the duration of the American commitment. Classical military logic demanded that the U.S. attack the locus of PAVN/NLF in the North. If that country could not be invaded, then the enemy's logistical system in Laos and Cambodia should be cut by ground forces, isolating the southern battlefield. However, political considerations limited U.S. military actions, mainly because of the memory of communist reactions during the Korean War. Ever present in the minds of diplomats, military officers, and politicians was the possibility of a spiraling escalation of the conflict into a superpower confrontation and the possibility of a nuclear exchange. Therefore, there would be no invasion of North Vietnam, the "neutrality" of Laos and Cambodia would be respected, and Rolling Thunder would not resemble the bombing of Germany and Japan during the Second World War.

President Johnson conferring with South Vietnamese President Nguyễn Văn Thiệu in July 1968.

These limitations were not foisted upon the military as an afterthought. Before the first U.S. soldiers came ashore at Da Nang, the Pentagon was cognizant of all of the parameters that would be imposed by their civilian leaders, yet they still agreed that the mission could be accomplished within them. Westmoreland believed that he had found a strategy that would either defeat North Vietnam or force it into serious negotiations. Attrition was to be the key. The general held that larger offensive operations would grind down the communists and eventually lead to a "crossover point" in PAVN/NLF casualties after which a decisive (or at least political) victory would be possible.

The one-year tour of duty deprived units of experienced leadership. As one observer put it, "we were not in Vietnam for 10 years, but for one year 10 times."[16] As a result, training programs were shortened. Some NCOs were referred to as "Shake 'N' Bake" to highlight their accelerated training. Unlike soldiers in World War II and Korea, there were no secure rear areas in which to get rest and relaxation.[citation needed] One unidentified soldier said to United Press International that there was nothing to do in Vietnam and therefore many of the men smoked marijuana. He said, "One of the biggest reasons that a lot of GIs do get high over here is there is nothing to do. This place is really a drag; it's a bore over here. Like right now sitting around here, we are getting loaded. Whereas, it doesn’t really get you messed up; that's I guess the main reason why we smoke it."[17]

American forces would conduct operations against PAVN forces, pushing them further back into the countryside away from the heavily populated coastal lowlands. In the backcountry the U.S. could fully utilize its superiority in firepower and mobility to bleed the enemy in set-piece battles. The cleaning-out of the NLF and the pacification of the villages would be the responsibility of the South Vietnamese military. The adoption of this strategy, however, brought Westmoreland into direct conflict with his Marine Corps commander, General Lewis W. Walt, who had already recognized the security of the villages as the key to success. Walt had immediately commenced pacification efforts in his area of responsibility, but Westmoreland was unhappy, believing that the Marines were being underutilized and fighting the wrong enemy. In the end, MACV won out and Westmoreland's search and destroy concept, predicated on the attrition of enemy forces, won the day.

Both sides chose similar strategies. PAVN, which had been operating a more conventional, large-unit war, switched back to small-unit operations in the face of U.S. military capabilities. The struggle moved to the villages, where the "hearts and minds" of the South Vietnamese peasants, whose cooperation was absolutely necessary to military success, would be won or lost. The U.S. had given responsibility for this struggle to the Army of the Republic of Vietnam (ARVN), whose troops and commanders were notoriously unfit for the task.

For the American soldier, whose doctrine was one of absolute commitment to total victory, this strategy led to a frustrating small-unit war. Most of the combat was conducted by units smaller than battalion-size (the majority at the platoon level). Since the goal of the operations was to kill the enemy, terrain was not taken and held as in previous wars. Savage fighting and the retreat of the communists was immediately followed by the abandonment of the terrain just seized. Combined with this was the anger and frustration engendered among American troops by the effective tactics of the NLF, who conducted a war of sniping, booby traps, mines, and terror against the Americans.

As a result of the conference held in Honolulu, President Johnson authorized an increase in troop strength to 429,000 by August 1966. The large increase in troops enabled MACV to carry out numerous operations that grew in size and complexity during the next two years. For U.S. troops participating in these operations (Operation Masher/White Wing, Operation Attleboro, Operation Cedar Falls, Operation Junction City and dozens of others) the war boiled down to hard marching through some of the most difficult terrain on the planet and weather conditions that were alternately hot and dry or cold and wet. It was the PAVN/NLF that actually controlled the pace of the war, fighting only when their commanders believed that they had the upper hand and then disappearing when the Americans and/or ARVN brought their superiority in numbers and firepower to bear. North Vietnam, utilizing the Ho Chi Minh and Sihanouk Trails, matched the U.S. at every point of the escalation, funneling manpower and supplies to the southern battlefields.

During the Vietnam War, the use of the helicopter, known as "Air Mobile", was an essential tool for conducting the war. In fact, the whole conduct and strategy of the war depended on it. Vietnam was the first time the helicopter was used on a major scale, and in such important roles. Search and destroy missions, for example, would have been nearly impossible without it. Helicopters allowed American commanders to move large numbers of troops to virtually anywhere, regardless of the terrain or roads. Troops could also be easily resupplied in remote areas. The helicopter also provided another new and vital capability: medical evacuation. It could fly wounded soldiers to aid stations very quickly, usually within the critical first hour. This gave wounded soldiers a higher chance of survival in Vietnam than in any previous war. The helicopter was also adapted for many other roles in Vietnam, including ground attack, reconnaissance, and electronic warfare. Without the helicopter, the war would have been fought very differently.[18]

By mid-1967, Westmoreland said that it was conceivable that U.S. forces could be phased out of the war within two years, turning over progressively more of the fighting to the ARVN.[19] That fall, however, savage fighting broke out in the northern provinces. Beginning below the DMZ at Con Tien and then spreading west to the Laotian border near Dak To, large PAVN forces began to stand their ground and fight. This willingness of the communists to remain fixed in place inspired MACV to send reinforcements from other sectors of South Vietnam. The Border Battles had begun.

Most of the PAVN/NLF operational capability was possible only because of the unhindered movement of men along the Ho Chi Minh Trail. To threaten this flow of supplies, the Marine Corps established a combat base on the South Vietnamese side of the Laotian frontier, near the village of Khe Sanh. The U.S. used the base as a border surveillance position overlooking Route 9, the only east-west road that crossed the border in the province. Westmoreland also hoped to use the base as a jump-off point for any future incursion against the Trail system in Laos. During the spring of 1967, a series of small-unit actions near Khe Sanh prompted MACV to increase its forces. These small unit actions and increasing intelligence information indicated that the PAVN was building up significant forces just across the border.

Indeed, PAVN was doing just that. Two regular divisions (and later elements of a third) were moving toward Khe Sanh, eventually surrounding the base and cutting off its only road access. Westmoreland, contrary to the advice of his Marine commanders, reinforced the outpost. As far as he was concerned, if the communists were willing to mass their forces for destruction by American air power, so much the better. He described the ideal outcome as a "Dien Bien Phu in reverse". MACV then launched the largest concentrated aerial bombardment effort of the conflict (Operation Niagara) to defend Khe Sanh. Another massive aerial effort was undertaken to keep the beleaguered Marines supplied. There were many comparisons (by the media, Americans military and political officials, and the North Vietnamese) to the possibility of PAVN staging a repeat of its victory at Dien Bien Phu, but the differences outweighed the similarities in any comparison.

MACV used this opportunity to field its latest technology against the North Vietnamese. A sensor-driven, anti-infiltration system known as Operation Igloo White was in the process of being field tested in Laos as the siege of Khe Sanh began. Westmoreland ordered that it be employed to detect PAVN troop movements near the Marine base and the system worked well. By March, the long-awaited ground assault against the base had failed to materialize and communist forces began to melt back toward Laos. MACV (and future historians) were left with only questions. What was the goal of the PAVN? Was the siege a real attempt to stage another Dien Bien Phu? Or had the battles near the border (which eventually drew in half of MACV's maneuver battalions) been a diversion, meant to pull forces away from the cities, where another PAVN offensive would soon commence?

General Westmoreland's public reassurances that "the light at the end of the tunnel" was near were countered when, on January 30, 1968, PAVN and NLF forces broke the truce that accompanied the Tết holiday and mounted their largest offensive thus far, in hopes of sparking a general uprising among the South Vietnamese. These forces, ranging in size from small groups to entire regiments, attacked nearly every city and major military installation in South Vietnam. The Americans and South Vietnamese, initially surprised by the scope and scale of the offensive, quickly responded and inflicted severe casualties on their enemies. The NLF was essentially eliminated as a fighting force and the places of the dead within its ranks were increasingly filled by North Vietnamese.

The PAVN/NLF attacks were speedily and bloodily repulsed in virtually all areas except Saigon, where the fighting lasted for three days, and in the old imperial capital of Huế, where it continued for a month. During the occupation of the historic city, 2,800 South Vietnamese were murdered by the NLF in the single worst massacre of the conflict. The hoped-for uprising never took place; indeed, the offensive drove some previously apathetic South Vietnamese to fight for the government. Another surprise for the communists was that the ARVN did not collapse under the onslaught, instead turning in a performance that pleased even its American patrons.

Final evacuation of Khe Sanh base complex, July 1, 1968.

After the Tet Offensive, influential news magazines and newspapers, including the Wall Street Journal, Time and the New York Times, increasingly began to characterize the war as a stalemate. What shocked and dismayed the American public was the realization that either it had been lied to or that the American military command had been dangerously overoptimistic in its appraisal of the situation in Vietnam. The public could not understand how such an attack was possible after being told for several years that victory was just around the corner. The Tet Offensive came to embody the growing credibility gap at the heart of U.S. government statements. These realizations and changing attitudes forced the American public (and politicians) to face hard realities and to reexamine their position in Southeast Asia. The days of an open-ended commitment to the conflict were over.

The psychological impact of the Tet Offensive effectively ended the political career of Lyndon Johnson. On March 11, Senator Eugene McCarthy won 42 percent of the vote in the Democratic New Hampshire primary. Although Johnson was not on the ballot, commentators viewed this as a defeat for the President. Shortly thereafter, Senator Robert Kennedy announced his intention to seek the Democratic nomination for the 1968 presidential election. On March 31, in a speech that took America and the world by surprise, Johnson announced that "I shall not seek, and I will not accept the nomination of my party for another term as your President" and pledged himself to devoting the rest of his term in office to the search for peace in Vietnam.[20] Johnson announced that he was limiting bombing of North Vietnam to just north of the Demilitarized Zone and that U.S. representatives were prepared to meet with North Vietnamese counterparts in any suitable place "to discuss the means to bring this ugly war to an end." A few days later, much to Johnson's surprise, North Vietnam agreed to contacts between the two sides. On May 13, what became known as the Paris peace talks began.[21]

On March 16, 1968, three companies of Task Force Barker, part of the Americal Division, took part in a search and destroy operation near the village of My Lai, in Quảng Nam Province. One of those three companies, Charlie Company, under the command of Lieutenant William Calley, entered the hamlet of Son My and proceeded to round up, rape, torture and murder as many of the inhabitants as could be found. (Citation needed.) Although not all of the members of the company participated, a significant number of them, led by Calley, did. He personally ordered the executions of hundreds of villagers in large groups. The killings ended only when an American helicopter crew, headed by Warrant Officer Hugh Thompson, Jr., discovered Calley's unit in the act and threatened to attack them with his aircraft's weapons unless they stopped. One of the soldiers on the scene was Ron Haeberle, a photographer for the newspaper, "Stars and Stripes", who took unobtrusive official black-and-white photos of the operation through the lens of his military-issued camera and color shots of the massacre with his personal camera. Although the operation appeared suspicious to Calley's superiors, it was forgotten.

In 1969, investigative journalist Seymour Hersh exposed the My Lai massacre in print, and the Haeberle photos were released to the world media. The Pentagon launched an investigation headed by General William R. Peers to look into the allegations. After a flurry of activity, the Peers Commission issued its report. It declared that "an atmosphere of atrocity" surrounded the event, concluding that a massacre had taken place and the crime had been covered up by the commander of the Americal Division and his executive officer. Perhaps 400 Vietnamese civilians, mostly old men, women, and children had been killed by Charlie company. Several men were charged in the killings, but only Calley was convicted. He was given a life sentence by a court-martial in 1970, but after numerous appeals he was finally set free; he had served just over three years of house arrest.

Richard Nixon had campaigned in the 1968 presidential election under the slogan that he would end the war in Vietnam and bring "peace with honor." However, there was no plan to do this, and the American commitment continued for another five years. The goal of the American military effort was to buy time, gradually building up the strength of the South Vietnamese armed forces, and re-equipping it with modern weapons so that they could defend their nation on their own. This policy became the cornerstone of the so-called Nixon Doctrine. As applied to Vietnam, it was labeled Vietnamization.

President Johnson in conversation with Chairman of the Joint Chiefs of Staff Earle Wheeler (center) and General Creighton Abrams (right).

Soon after Tet, General Westmoreland was promoted to Army Chief of Staff and he was replaced by his deputy, General Creighton W. Abrams. Because of the change in American strategy posed by Vietnamization, Abrams pursued a very different approach. The U.S. was gradually withdrawing from the conflict, and Abrams favored smaller-scale operations aimed at PAVN/NLF logistics, more openness with the media, less indiscriminate use of American firepower, elimination of the body count as the key indicator of battlefield success, and more meaningful cooperation with South Vietnamese forces.

Vietnamization of the war, however, created a dilemma for US forces: the strategy required that US troops fight long enough for the ARVN to improve enough to hold its own against Communist forces. Morale in the US ranks rapidly declined during 1969-1972, as evidenced by declining discipline, worsening drug use among soldiers, and increased "fraggings" of US officers by disgruntled troops.

One of Nixon's main foreign policy goals had been the achievement of a breakthrough in U.S. relations with the People's Republic of China and the Soviet Union. An avowed anti-communist since early in his political career, Nixon could make diplomatic overtures to the communists without being accused of being "soft on communism." The result of his overtures was an era of détente that led to nuclear arms reductions by the U.S. and Soviet Union and the beginning of a dialogue with China. In this context, Nixon viewed Vietnam as simply another limited conflict forming part of the larger tapestry of superpower relations; however, he was still determined to preserve South Vietnam until such time as he could not be blamed for what he saw as its inevitable collapse (or a "decent interval", as it was known). To this end he and National Security Advisor Henry Kissinger employed Chinese and Soviet foreign policy gambits to successfully defuse some of the anti-war opposition at home and secured movement at the negotiations that had begun in Paris.

China and the Soviet Union had been the principal backers of North Vietnam's effort through large-scale military and financial aid. The two communist superpowers had competed with one another to prove their "fraternal socialist links" with the regime in Hanoi. The North Vietnamese had become adept at playing the two nations off against one another. Even with Nixon's rapprochement, their support of North Vietnam increased significantly in the years leading up to the U.S. departure in 1973, enabling the North Vietnamese to mount full-scale conventional offensives against the South, complete with tanks, heavy artillery, and the most modern surface-to-air missiles.

The credibility of the U.S. government again suffered in 1971 when The New York Times, The Washington Post and other newspapers serially published The Pentagon Papers (actually U.S.-Vietnam Relations, 1945-1967). This top-secret historical study of the American commitment in Vietnam, from the Franklin Roosevelt administration until 1967, had been contracted to the RAND Corporation by Secretary of Defense McNamara. The documents were leaked to the press by Daniel Ellsberg, a former State Department official who had worked on the study.

The Pentagon Papers laid out the missteps taken by four administrations in their Vietnam policies. For example, they revealed the Johnson administration's obfuscations to Congress concerning the Gulf of Tonkin incidents that had led to direct U.S. intervention; they exposed the clandestine bombing of Laos that had begun in 1964; and they detailed the American government's complicity in the death of Ngô Đình Diệm. The study presented a continuously pessimistic view of the likelihood of victory and generated fierce criticism of U.S. policies.

The importance of the actual content of the papers to U.S. policy-making was disputed, but the window that they provided into the flawed decision-making process at the highest levels of the U.S. government opened the issue for other questions. Their publication was a news event and the government's legal (Nixon lost to the Supreme Court) and extra-legal efforts (the "Plumbers" break-in at the office of Ellsberg's psychiatrist committed to gain material to discredit him, was one of the first steps on the road to Watergate) carried out to prevent their publication—mainly on national security grounds—then went on to generate yet more criticism and suspicion of the government by the American public.

By 1969 the policy of non-alignment and neutrality had worn thin for Prince Sihanouk, ruler of Cambodia. Pressures from the right in Cambodia caused the prince to begin a shift away from the pro-left position he had assumed in 1965–1966. He began to make overtures for normalized relations with the U.S. and created a Government of National Salvation with the assistance of the pro-American General Lon Nol. Seeing a shift in the prince's position, President Nixon ordered the launching of a top-secret bombing campaign, targeted at the PAVN/NLF Base Areas and sanctuaries along Cambodia's eastern border. The massive B-52 strikes conducted over 14 months were the beginning of a deluge that delivered approximately 2,756,941 tons of bombs on Cambodia over the next five years. This was more than the total tonnage that the Allies dropped during all of the Second World War, including the bombs that struck Hiroshima and Nagasaki. According to historians Ben Kiernan and Taylor Owen, "Cambodia may well be the most heavily bombed country in history."[22]

President Nixon explains the expansion of the war into Cambodia.

On March 18, 1970, Sihanouk, who was out of the country on a state visit, was deposed by a vote of the National Assembly and replaced by General Lon Nol. Cambodia's ports were immediately closed to North Vietnamese military supplies, and the government demanded that PAVN/NLF forces be removed from the border areas within 72 hours. On March 29, 1970, the Vietnamese had taken matters into their own hands and launched an offensive against the Cambodian army. A force of North Vietnamese quickly overran large parts of eastern Cambodia reaching to within 15 miles (24 km) of Phnom Penh allowing their allies, the Chinese-supported Khmer Rouge to extend their power. Nixon ordered a military incursion into Cambodia by U.S. and ARVN troops in order to both destroy PAVN/NLF sanctuaries bordering South Vietnam and to buy time for the U.S. withdrawal. During the Cambodian Campaign, U.S. and ARVN forces discovered and removed or destroyed a huge logistical and intelligence haul in Cambodia.

The incursion also sparked large-scale demonstrations on and closures of American college campuses. The expansion of the conflict into Cambodia was seen as an expansion of the conflict into yet another country, nullifying Nixon's promises of de-escalating the war. During the ensuing protests, four students were killed and a score were wounded by Ohio National Guardsmen during a demonstration at Kent State University. Two other students were killed at Jackson State University in Mississippi. In an effort to lessen opposition to the U.S. commitment, Nixon announced on October 12 that the U.S. would withdraw 40,000 more troops from Vietnam before Christmas.

Following the coup, Sihanouk arrived in Beijing, where he established and headed a government in exile, throwing his substantial personal support behind the Khmer Rouge, the North Vietnamese, and the Laotian Pathet Lao.

In 1971 the U.S. authorized the ARVN to carry out an offensive operation aimed at cutting the Ho Chi Minh Trail in southeastern Laos. Besides attacking the PAVN logistical system (which would buy time for the U.S. withdrawal) the incursion would be a significant test of Vietnamization. Backed by U.S. air and artillery support (American troops were forbidden to enter Laos), the ARVN moved across the border along Route 9, utilizing the abandoned Marine outpost of Khe Sanh as a jumping-off point. At first, the incursion went well, but unlike the Cambodian operation of 1970, the PAVN decided to stand and fight, finally mustering around 60,000 men on the battlefield.

The North Vietnamese first struck the flanks of the ARVN column, smashed its outposts, and then moved in on the main ARVN force. Unlike previous encounters during the conflict, the PAVN fielded armoured formations, heavy artillery, and large amounts of the latest anti-aircraft artillery. After two months of savage fighting, the ARVN retreated back across the border, closely pursued by the North Vietnamese. One half of the invasion force was killed or captured during the operation, and Vietnamization was seen as a failure.

On August 18, Australia and New Zealand decided to withdraw their troops from the conflict. The total number of U.S. forces in South Vietnam dropped to 196,700 on October 29, 1971, the lowest level since January 1966. On November 12, 1971, Nixon set a February 1, 1972 deadline for the removal of another 45,000 troops.

Vietnamization received another severe test in the spring of 1972 when the North Vietnamese launched a massive conventional offensive across the Demilitarized Zone. Beginning on March 30, the Easter Offensive (known as the Nguyễn Huệ Offensive to the North Vietnamese) quickly overran the three northernmost provinces of South Vietnam, including the provincial capital of Quảng Trị City. PAVN forces then drove south toward Huế.

Early in April, PAVN opened two additional operations. The first, a three-division thrust supported by tanks and heavy artillery, advanced out of Cambodia on April 5. The North Vietnamese seized the town of Loc Ninh and advanced toward the provincial capital of An Lộc in Bình Long Province. The second new offensive, launched from the tri-border region into the Central Highlands, seized a complex of ARVN outposts near Dak To and then advanced toward Kon Tum, threatening to split South Vietnam in two.

The U.S. countered with a buildup of American airpower to support ARVN defensive operations and to conduct Operation Linebacker, the first offensive bombing of North Vietnam since Rolling Thunder had been terminated in 1968. The PAVN attacks against Huế, An Lộc, and Kon Tum were contained and the ARVN launched a counteroffensive in May to retake the lost northern provinces. On September 10, the South Vietnamese flag once again flew over the ruins of the Citadel of Quảng Trị City, but the ARVN offensive then ran out of steam, conceding the rest of the occupied territory to the North Vietnamese. South Vietnam had countered the heaviest attack since Tet, but it was very evident that it was totally dependent on U.S. airpower for its survival. Meanwhile, the withdrawal of American troops, who numbered less than 100,000 at the beginning of the year, was continued as scheduled. By June only six infantry battalions remained. On August 12, the last American ground combat division left the country. However, the US continued to operate the base At Long Binh. Combat patrols continued there until November 11 when the US handed over the base to the South Vietnamese. After this, only 24,000 American troops remained in Vietnam and President Nixon announced that they would stay there until all US POW's were freed.

At the beginning of the North Vietnamese invasion, the media, including conservative commentator William F. Buckley, predicted the downfall of the Republic of Vietnam; Buckley even called for the firing of General Creighton Abrams as an incompetent military leader. But the ARVN succeeded in defeating General Giap and his huge invading army. His forces were shattered at the Battle of An Lộc, where he threw several divisions at the entrenched South Vietnamese forces, ultimately losing over half of his army as casualties. General Giap's loss and subsequent retreat was viewed as so great a failure by the North Vietnamese Communist Party that Giap was relieved of his command. Although ARVN troops withstood and repelled the massive PAVN attack at An Lộc, American air power seems to have been a key to the ARVN success, just as it had been a key factor in supporting US ground forces when they operated in South Vietnam prior to 1972. Thus, the 1973 withdrawal of US military support and passage of Congressional resolutions cutting off U.S. funding for combat activities in Indochina (H.R. 9055 and H.J.Res. 636) opened the way for the 1975 defeat of the Republic of Vietnam.

During the run-up to the 1972 presidential election, the war was once again a major issue. An antiwar Democrat, George McGovern, ran against President Nixon. The president ended Operation Linebacker on October 22 after the negotiating deadlock was broken and a tentative agreement had been hammered out by U.S. and North Vietnamese representatives at the peace negotiations in Paris. The head of the U.S. negotiating team, Henry Kissinger, declared that "peace is at hand" shortly before election day, dealing a death blow to McGovern's already doomed campaign. Kissinger had not, however, counted on the intransigence of South Vietnamese President Thieu, who refused to accept the agreement and demanded some 90 changes in its text. These the North Vietnamese refused to accept, and Nixon was not inclined to put too much pressure on Thieu just before the election, even though his victory was all but assured. The mood between the U.S. and North further turned sour when Hanoi went public with the details of the agreement. The Nixon Administration claimed that North Vietnamese negotiators had used the pronouncement as an opportunity to embarrass the President and to weaken the United States. White House Press Secretary Ron Ziegler told the press on November 30 that there would be no more public announcements concerning U.S. troop withdrawals from Vietnam since force levels were down to 27,000.

Because of Thieu's unhappiness with the agreement, primarily the stipulation that North Vietnamese troops could remain "in place" on South Vietnamese soil, the negotiations in Paris stalled as Hanoi refused to accept Thieu's changes and retaliated with amendments of its own. To reassure Thieu of American resolve, Nixon ordered a massive bombing campaign against North Vietnam utilizing B-52s and tactical aircraft in Operation Linebacker II, which began on December 18 with large raids against both Hanoi and the port of Haiphong. Nixon justified his actions by blaming the impasse in negotiations on the North Vietnamese, causing one commentator to describe his actions as "War by tantrum." Although this heavy bombing campaign caused protests, both domestically and internationally, and despite significant aircraft losses over North Vietnam, Nixon continued the operation until December 29. He also exerted pressure on Thieu to accept the terms of the agreement reached in October.

On January 15, 1973, citing progress in peace negotiations, Nixon announced the suspension of all offensive actions against North Vietnam, to be followed by a unilateral withdrawal of all U.S. troops. The Paris Peace Accords on "Ending the War and Restoring Peace in Vietnam" were signed on January 27, officially ending direct U.S. involvement in the Vietnam War.

The agreement called for the withdrawal of all U.S. personnel and an exchange of prisoners of war. Within South Vietnam, a cease-fire was declared (to be overseen by a multi-national, 1,160-man International Control Commission force) and both ARVN and PAVN/NLF forces would remain in control of the areas they then occupied, effectively partitioning South Vietnam. Both sides pledged to work toward a compromise political solution, possibly resulting in a coalition government. To maximize the area under their control, both sides in South Vietnam almost immediately engaged in land-grabbing military operations, which turned into flashpoints. The signing of the Accords was the main motivation for the awarding of the 1973 Nobel Peace Prize to Henry Kissinger and to leading North Vietnamese negotiator Le Duc Tho. A separate cease-fire had been installed in Laos in February. Five days before the signing of the agreement in Paris, President Lyndon Johnson, whose presidency had been tainted with the Vietnam issue, died.

The first U.S. prisoners of war were released by North Vietnam on February 11, and all U.S. military personnel were ordered to leave South Vietnam by March 29. As an inducement for Thieu's government to sign the agreement, Nixon had promised that the U.S. would provide financial and limited military support (in the form of air strikes) so that the South would not be overrun. But Nixon was fighting for his political life in the growing Watergate scandal and facing an increasingly hostile Congress that withheld funding. The President was able to exert little influence on a hostile public long sick of the Vietnam War.

Thus, Nixon (or his successor Gerald Ford) was unable to fulfill his promises to Thieu. At the same time, aid to North Vietnam from the Soviet Union increased. With the U.S. no longer heavily involved, both the U.S. and the Soviet Union no longer saw the war as significant to their relations. The balance of power shifted decisively in North Vietnam's favor, and the North subsequently launched a major military offensive, the Ho Chi Minh Campaign, against the South that culminated in the surrender of the Republic of Vietnam to PAVN forces on April 30, 1975.