Richard Nixon came to the presidency with a reputation as an unabashed cold warrior. He had begun his career as a young congressman who came to national prominence with his vigorous insistence of the guilt of Alger Hiss. In the House and later in the Senate, Nixon was viewed as a slightly less abrasive version of strident anti-communist Senator Joseph McCarthy. Added to the Republican presidential ticket with Dwight D. Eisenhower as a concession to conservative Republicans, Nixon served two terms as vice president and then narrowly lost his own race for the presidency to John F. Kennedy in 1960. Rising from political oblivion after his defeat for the California governorship in 1962, Nixon’s narrow presidential victory in 1968 was indicative of his legendary determination. Unlike his predecessor, Nixon came to the presidency with a strong interest in foreign affairs, believing that a president had a much greater degree of freedom of action in foreign policy than in domestic issues. Nixon also saw the war in Vietnam as only one of many Cold War issues, and not as an isolated issue. He hoped that, by pursuing better relations with the Soviet Union and China, he could get them to put pressure on their North Vietnamese allies. Nixon called this strategy "linkage." Nixon had avoided explicit statements on Vietnam during the campaign, promising simply "peace with honor." Critical of anti-war Democrats, who Nixon charged wanted to abandon South Vietnam, he pledged to end the war without surrendering South Vietnam to the communists.

Nixon relied on Dr. Henry Kissinger for foreign policy advice. Kissinger was a Jewish refugee from Nazi Germany who had come to America as a teenager in 1938. A Harvard professor, Kissinger wrote a book, Nuclear Weapons and Foreign Policy, in 1958 that had established him as a major specialist on foreign affairs and defense issues. During the 1960s, Kissinger had given his advice to both Republicans and Democrats, maintaining contacts with both political parties. Originally an advisor to one of Nixon’s rivals for the Republican presidential nomination, Governor Nelson Rockefeller of New York, Kissinger had used his Democratic contacts to inform Nixon of Johnson’s Vietnam-related actions during the campaign. After the election, Kissinger was named as Nixon’s National Security Advisor. In this position, Kissinger quickly became viewed as the administration’s primary foreign policy spokesperson as Nixon ignored the state department, preferring to retain control of foreign policy in the White House.

Nixon believed that his reputation as a hard-line anti-communist would assist him in dealing with the North Vietnamese. He described this to an aide as the "Madman Theory:

Nixon believed that the North Koreans had responded to President Eisenhower’s threats to use nuclear weapons in Korea by finally agreeing to a peace settlement in 1953 and hoped for a similar ending in Vietnam.

Once again, American leadership had failed to comprehend the mind of their opposition. Secure in their positions of power, the North Vietnamese leadership had proven impervious (totally resistant) to American threats. As an American military expert on North Vietnam, Brian Jenkins, later said, "The pursuit of their goals had taken up their entire lives. And the notion that one could change the mind of a number of people sixty and seventy years old … in Hanoi was a bit far-fetched." As Prime Minister Pham Van Dong had told a journalist in the late 1960s, "There is nothing else in our history except struggle. Struggle against foreign invaders, always more powerful than ourselves; struggle against nature—and we’ve had nowhere else to go, we’ve had to fight things out where we were." Soon after Nixon became president, the communists opened a major offensive in an eerie repeat of the Tet Offensive of the previous year:

1,140 Americans died in these attacks. Nixon’s response was to launch B-52 attacks against communist sanctuaries in Cambodia. The bombings, known as Operation Menu, were kept secret out of the fear of the public response to the widening of the war. Prince Norodom Sihanouk, the ruler of Cambodia, had allowed the North Vietnamese to violate his country’s neutrality; however, by late 1967 he was becoming increasingly worried at the increased North Vietnamese presence. In January 1968, he told a U.S. representative that he would not oppose U.S. troops entering his country in "hot pursuit" of communist troops. Johnson did not want to send troops into Cambodia, although some U.S. special forces did conduct limited sabotage missions. The joint chiefs of staff urged Nixon to lift the restriction and the communist assault provided the justification for bombing Cambodia. Nixon told his advisors that the "only way" to get the communists to negotiate was "to do something on the military front…." Operation Menu provided a way to turn up the heat without resuming the bombing of the North, which would have incited domestic opposition and given the communists an excuse to further delay the stalled peace talks in Paris. The secret bombing went on for fourteen months and dropped four times the tonnage that the U.S. had dropped on Japan in World War II. In May 1969, the New York Times published a story on the bombings. Nixon was outraged and ordered the FBI to institute wiretaps on four journalists and thirteen government officials. This search for leaks (government information given to the media without government approval) would ultimately lead to the Watergate Scandal.

The Cambodian bombings had no discernible (noticeable) effect of the North Vietnamese. Neither did Nixon’s efforts to pressure the USSR to restrain its ally. Despite the fact that the Soviets were giving $1 billion to Hanoi, they had very little leverage because of the conflict between the USSR and China. The Soviets could not afford to be accused by the Chinese of abandoning a fellow socialist country. Asked to define the degree of influence that the Soviets had over the North Vietnamese, a Soviet official said, "There is absolutely none." On May 14, 1969, Nixon unveiled an eight point peace proposal in a televised address to the American people. The key feature was a phased twelve-month withdrawal of both U.S. and North Vietnamese troops from the South. The North Vietnamese were uninterested in this proposal (a similar proposal had already been offered by President Johnson in 1966). After Tet, they realized that the Vietcong were not strong enough to hold out against the South Vietnamese Army without the support of North Vietnamese regulars. The communists continued to insist on the resignation of South Vietnam’s President Thieu and the formation of a coalition government that included the Vietcong.

In June, Ho Chi Minh accepted Nixon’s offer to open secret talks in Paris between Kissinger and Hanoi’s top negotiator Le Duc Tho. These secret talks began in August. In the meantime, Nixon announced that, for the first time, the U.S. would be cutting its forces in Vietnam:

By withdrawing American troops through Vietnamization, Nixon hoped to blunt criticism of the war at home long enough to exert enough military pressure on North Vietnam to convince its leaders to negotiate a peace that would allow for the survival of the South Vietnamese regime. Under this plan, the South Vietnamese military was to be expanded from 850,000 to over one million. In addition, the U.S. pledged to greatly expand the export of military equipment to the South. This process had actually begun in 1968 in the aftermath of the Tet Offensive as the Johnson administration placed greater pressure on the South Vietnamese to shoulder a larger burden of the fighting. Tougher conscription laws, for the first time requiring the service of 15-19 year olds, led to an 80,000 man increase in South Vietnamese forces. The Nixon administration’s material aid provided modern weaponry for the first time to the South Vietnamese. By 1971, the South Vietnamese Airforce had grown to the fourth largest in the world. Nixon hoped that the increased strength of the South Vietnamese could permit a phased U.S. withdrawal without a collapse of the Saigon government.

In September 1969, Ho Chi Minh died at age sixty-nine of a heart attack. At his funeral, Le Duan, First Secretary of the Communist Party, read from Ho’s political will and pledged to continue the military struggle until all foreign aggressors were removed from Vietnamese soil. Although the U.S. initially hoped for a softening from Hanoi in the wake of Ho’s death, the leadership of the North remained unified and there was no change in the North’s attitudes toward the war. Frustrated by Hanoi’s imperviousness to U.S. diplomatic efforts and the bombing of Cambodia, Kissinger advocated that the bombing of the North be resumed. "I can’t believe," Kissinger told his staff, "that a fourth-rate power like North Vietnam doesn’t have a breaking point." Three of his aides dissented, arguing that efforts to increase the pressure on Hanoi had always failed in the past. They advocated accepting a settlement in place, permitting North Vietnamese units to remain where they were in the South and the formation of a coalition government. Kissinger rejected these suggestions and took his plans for a "savage, punishing" blow against the North to the president. Upon the advice of Secretary of Defense Melvin Laird, Nixon rejected Kissinger’s proposal, commenting, "I’m not sure we’re ready for this." Although unsuccessful in making progress in the peace talks (both official and secret), Nixon’s withdrawal of American troops was extremely popular with the war-weary American people. In early September, a public opinion poll indicated that 71% of the American people approved of the president’s Vietnam policies. On September 16, Nixon announced an additional withdrawal of 35,000 troops (later in the year a third cut of 50,000 was announced to be effective by April 15, 1970).

Despite this degree of public approval, Nixon was frustrated by the continuing criticism of his policies both in Congress and by the anti-war movement. A series of resolutions were offered in Congress to require the removal of all U.S. troops by the end of 1970. In addition, the anti-war movement planned a series of moratoriums (suspension of normal activities) to protest the war The moratoriums were efforts to expand the anti-war protests from college campuses. The first moratorium took place on October 15:

On Moratorium Day, President Nixon directed an assistant to tell the press he had been conducting "business as usual." Nixon believed that the anti-war movement was encouraging Hanoi to continue to resist any compromise in the peace talks, and thereby harming his efforts to reach a settlement. On November 3, Nixon had spoken on what he believed was the danger of domestic dissent: "Let us be united for peace. Let us be united against defeat. Because let us understand: North Vietnam cannot defeat or humiliate the United States. Only Americans can do that." One of his top assistants, John Ehrlichman, explained: "His position was that he’d been elected as the individual under the constitutional system responsible for the conduct of foreign policy and the waging of war, if you please, and that foreign policy just couldn’t be made in the streets." Of the protests, Nixon said, "Under no circumstances will I be affected." He addressed the topic in a televised speech to the country on November 24:

While Nixon appealed to the "silent majority" (and the polls continued to show that a majority of the people supported his policies), the anti-war demonstrations continued. A second moratorium held on November 13-15 was even larger than the demonstration of the previous month. On November 13, 40,000 people marched in a candlelight vigil to the White House. Two days later over 250,000 marched in the freezing cold from the Capitol to the Washington Monument. What remained clear was the fact that America remained deeply divided over the war. A Harris poll in December showed that 46% of the public sympathized with the goals of the anti-war moratoriums, while 45% disagreed with their goals.

The war in Vietnam in 1969 was dramatically different from just two years before. Prior to 1969, the morale of the troops had remained relatively high. Desertions from the armed forces were at a lower rate than they had been in World War II and Korea. But between 1969 and 1971 the desertion rate quadrupled. Draftees were now serving in Vietnam who had been at home to see the television coverage of Tet, Khe Sanh, and the massive anti-war demonstrations of 1967-1968. While a majority of Americans no longer believed that victory in Vietnam was attainable, men were still being sent to Vietnam. Even the announced troop withdrawals contributed to declining morale. To many soldiers, their country was leaving Vietnam, but they were staying. A common slogan was, "Don’t be the last GI to die in ‘Nam."

One battle, fought in May 1969, seemed to symbolize the frustration and senselessness of the continuing war. The military command in Saigon issued orders for a massive search and destroy mission near the Laotian border. For ten days U.S. and South Vietnamese troops made their way up Apbia mountain range under incredible communist gunfire. Capture of one hill, dubbed "Hamburger Hill" by the soldiers, took eight days and eleven charges, costing 46 American lives and leaving 360 wounded. Like so many other points taken at great cost during the war, the hill was soon abandoned to the communists. Left behind was a solitary sign, "Hamburger Hill: Was it worth it?" The general who ordered the attack defended his decision by pointing to the fact that the troops had discovered evidence of a North Vietnamese regimental command post and that 630 communist troops had been killed. Secretary of Defense Laird was so appalled by the American casualties and the seeming unimportance of the objective that he ordered the U.S. field commander, General Creighton Abrams, not to conduct anymore large-scale operations like Hamburger Hill. A month later, Laird said: "We have to change the emphasis so that American forces in Vietnam can move forward to train and modernize the South Vietnamese forces, rather than fighting so much the war themselves." Although major clashes of forces were avoided, casualties still continued to mount in smaller operations. For the small percentage of U.S. troops still engaged in ground operations, the war became one of endless patrols, hours of boredom and aggravation, punctuated by moments of terror supplied by mines and ambushes. On the average, 800 Americans were killed and 6,000 wounded per month in 1969. Life magazine chose to dramatize the cost of the war by publishing the photographs of 242 men killed during a single week of the war. Page after page of men appeared in a high school yearbook-like format hammering home the cost of the war to the American public.

As more and more Americans concluded that the war could not be won, these feelings could not help but be reflected in the attitudes of the soldiers in Vietnam. As one marine described it, "I think the major aim of anybody over there at the time was just to take care of himself. The main objective was just to live through it, to get out of there." Soldiers began to avoid combat. Orders to patrol were ignored, sometimes with the acquiescence (agreement) of field officers, at other times in defiance of them. U.S. Army convictions for "mutiny and other acts involving willful refusal" rose from 82 in 1968, to 117 in 1969, and 131 in 1970. For others, drugs supplied a release. A small quantity of heroin, which sold on the street in the U.S. for $50, could be easily obtained in Vietnam for $2. Between 1969 and 1971 heroin use rose from 5% of enlisted personnel to 22%. Marijuana use was estimated at 58%. In 1971, fewer than 5,000 American soldiers were hospitalized due to war wounds. Four times that number (20,529) required treatment for drug abuse. A growing resentment developed between the small number of men still involved in combat and those in the relative safety of military headquarters:

Overzealous officers soon became targets for their own men. Known as "fragging," the number of officers killed by their own men between 1969 and 1971 was officially estimated at 83 with 730 documented attempts. It was commonly reported that a $10,000 bounty had been placed on the head of Lieutenant-Colonel Weldon Honeycutt who had ordered and led the Hamburger Hill assault (despite several fragging attempts, Honeycutt survived the war). A U.S. Army captain described a fragging incident in 1970:

A 1971 military report summarized the declining state of U.S. forces: "By every conceivable indicator, our army that now remains in Vietnam is in a state approaching collapse with individual units avoiding or having refused combat, murdering their officers and non-commissioned officers, drug-ridden and dispirited where not near-mutinous."

In the midst of the peace moratoriums during the fall of 1969, the American public was shocked to learn that American troops had been involved in atrocities previously only associated with America’s enemies in the Second World War. On November 13, a story by journalist Seymour Hersh, entitled "Massacre at My Lai 4," appeared in numerous newspapers throughout the country. The article alleged that U.S. Marines had participated in a massacre of civilians at the village of My Lai in northern South Vietnam in March 1968:

My Lai-4 was one of several hamlets in the village of Son My. The area had a reputation as a Vietcong stronghold and was known to Americans as "Pinkville." Soldier Tim O’Brien, who was involved in searching the area a year after the massacre, described the area: "I knew it was a bad place. We were afraid to go to Pinkville. It was a sullen, hostile, unpeopled place. We’d go among the My Lai villages and there were never any people: deserted and yet there were smoldering fires—people obviously lived there. It was a place where men died. It was a heavily mined area." Pinkville was considered to be a "free-fire zone" in which all civilians were automatically suspected of being Vietcong or communist supporters. The villages had already been subjected to numerous bombing raids as well as artillery and napalm attacks. By March 1968, approximately 70% of the homes in the area had already been destroyed.

On February 25, 1968, a patrol from Charlie Company had stumbled into a minefield in the area. Six soldiers were killed and another twelve severely wounded. The soldiers blamed the people of My Lai because they believed that they must have known the location of the minefield, but did nothing to warn the Americans. In reprisal, at least two members of the company assaulted, raped, and killed Vietnamese women in the area. These reprisals had resulted in a complaint to battalion headquarters and the company commander, Captain Ernest Medina, was told to tell his men to "cool it" in dealing with civilians. After taking more casualties on March 14, the battalion commander, Lieutenant-Colonel Frank A. Barker Jr. told Medina that a guerrilla force of 250 men was operating out of My Lai-4. An operation was planned for Saturday March 16^th because intelligence reports indicated that on Saturdays the women and children left the village at 7 a.m. to go to market. Medina was ordered to attack the village at that hour and destroy it.

The night before the attack Medina had briefed his platoon leaders. He told them that they would be outnumbered 2:1 and to expect opposition to their landing. Lieutenant Calley’s First Platoon would lead the way into the village. Their orders were to "… aggressively close with the enemy … and destroy his fighting capabilities … Burn the houses…. Kill the livestock… Destroy the rice… Leave nothing behind for the enemy to use in the future."

Calley’s men landed at 7:22 following an artillery barrage. Expecting opposition, Calley’s men found only an eerie quiet. After securing the landing zone for the next platoon, Calley’s thirty men moved into the village. On the way, Private Paul Meadlo recalled that someone spotted a Vietnamese civilian. Sergeant David Mitchell ordered the men to shoot the "gook." The men began shooting. Sergeant Charles West recalled, "When the attack started, it couldn’t have been stopped by anyone. We were mad and we had been told that only the enemy would be there when we landed…. We were going in for a fight and for our dead buddies…. We started shooting everything and everybody we saw." There was so much shooting that many of the men initially thought that they were under attack. When the platoon entered the village, they found that it was not deserted as they had been told to expect. Grenades were thrown into the thatched roof huts and people were machine gunned as they ran from them. In the village, Calley ordered his men to gather the Vietnamese, mostly women, older men, and children, together. Later Calley wrote that Medina had criticized him for moving too slow and ordered him to "waste all those goddamn people." Meadlo was then ordered by Calley "to take care of" a group of the civilians. When Calley returned later, Meadlo was still guarding his prisoners and Calley was irate, yelling at Meadlo, "Why haven’t you wasted them yet?" The prisoners were then gunned down. Another group of prisoners had been collected beside a drainage ditch. Calley ordered the civilians pushed into a ditch, striking one woman with his rifle as he forced her into the ditch. Then Calley began firing into the ditch and ordered his men to join in. Some soldiers refused but most fired into the ditch. Killings took place all over the village. Old men were bayoneted and one was thrown down a well in which a hand grenade was then tossed. Women and young girls were raped.

Warrant Officer Hugh Thompson Jr. observed the activity in the ditch from his helicopter. He marked the area with smoke so that the wounded could be found and treated. While marking the area, Thompson saw Medina shoot a young girl. He radioed his observations to military headquarters, landed, and evacuated sixteen wounded children. Haeberle, an Army photographer, took pictures of GIs burning huts and food supplies as well as the dead bodies piled in the drainage ditch. Estimates of the dead ranged from the army’s official total of 200 to individual surveys that placed the total civilian deaths in the area that day as high as 700. A private later testified that he "didn’t remember seeing one military age male in the entire place, dead or alive."

Colonel Barker had witnessed the firing from a helicopter overhead and ordered Medina to stop shooting. Thompson filed an official report of his observations and the radio communication between the commanders had been recorded. After the attack, Medina told his men that there would probably be an investigation and not to talk to anyone outside the company about the events in My Lai that day. Two weeks after the attack on My Lai, Colonel Barker’s combat action report described the attack as "well-planned, well-executed, and successful." Colonel Orrin Henderson, the brigade commander, conducted the first official investigation. His report, compiled without interviewing any of Charlie Company, acknowledged that civilians had been killed, but blamed artillery and helicopter fire.

The story only eventually emerged in the following year due to Ridenhour’s persistence. Finally two members of the House of Representatives, Morris Udall and Mendel Rivers, demanded a Pentagon investigation. Lieutenant-General William Peers conducted the investigation. Peers eventually concluded:

Thirteen soldiers were eventually charged with war crimes in regard to My Lai. An additional twelve were charged with the cover-up. Of these, only Lieutenant Calley was found guilty. Medina denied ordering Calley to kill everyone in the village and was acquitted. Calley was sentenced to life imprisonment in March 1970. A Newsweek poll showed that 79% of the American public disapproved of the verdict. The majority of those asked believed that Calley was "being made the scapegoat for the actions of others above him." Most surprisingly, 50% of the respondents believed that My Lai was a common incident in Vietnam and not an isolated case. Less than a week after the verdict, President Nixon ordered that Calley be removed from his cell in the base stockade at Fort Benning, Georgia and allowed to return to his quarters under house arrest while his case was being appealed. Although the courts denied all of Calley’s appeals, Nixon pardoned him in 1974 and he was released.

My Lai was not a totally isolated incident, yet it was probably on a greater scale than other atrocities committed against civilians. The frustration of not being able to discriminate between innocent civilians and Vietcong was undoubtedly responsible for much of the killing of innocents. Many American soldiers had a lesser degree of respect for human life when it came to the Vietnamese. Vietnamese civilians were usually referred to as "gooks," "dinks," and "slopes" by the Americans. While relations with civilians near secure base camps might be friendly, in the rural countryside all civilians were feared as possible Vietcong or Vietcong sympathizers. Marine medic Jack McCloskey believed that the training American soldiers received contributed to this attitude: "It was taught to us, go into this Ville, and you have to blow everything away in this Ville. Your basic mistrust of the Vietnamese people is already ingrained in you: anything with slat eyes was a ‘gook’—they were not human beings." As in My Lai, many atrocities occurred after units had taken casualties, often from booby traps or mines that were so close to civilian areas that soldiers either believed that they were planted by the civilians or with their knowledge. Tim O’Brien described this revenge factor in his telling of an encounter with the Vietcong in the villages of My Lai a year after the massacre. After taking casualties in an engagement with the Vietcong, O’Brien tells of entering the villages:

After leaving the village, the men were exposed to Vietcong sniper fire and then were mortared at night. Then they took their retaliation:

Civilians die in any war, yet examined in the light of the original objective "to win the hearts and minds" of the people of South Vietnam, the practical realities of guerrilla war often served only to antagonize the populace and lose support.

The tempered reaction of the American people to atrocities committed by U.S. troops was affected in part by the treatment of American prisoners of war. 766 Americans were held as prisoners in North Vietnam during the war. Over 600 of the Americans were pilots. The prisoners were kept under horrible conditions in jails such as the infamous "Hanoi Hilton," an old French prison in the center of Hanoi, and subjected to long stretches of solitary confinement and torture. Although North Vietnam had pledged to abide by the terms of the 1949 Geneva Convention for the humane treatment of prisoners, they considered the bombing a "crime against humanity," releasing them from their obligations toward downed pilots. The purpose of the torture was often to force the prisoners to make propaganda statements against the bombing as evidenced by this account of a prisoner statement in 1967:

Stratton’s deep bows were designed to show Americans that his following statement condemning the bombing was being done under duress. Another American, forced to read a similar statement, frequently blinked his eyes, spelling out "torture" in Morse Code. Fifteen percent of the acknowledged American captives died in captivity. This was lower than the percentage that died in the Korean War (38%) and at the hands of the Japanese during World War II (40%), but a far higher percentage than died in German hands (2%). News reports about the mistreatment of communist prisoners at the hands of the South Vietnamese and, to a lesser degree, by the Americans did little to stem the outrage of Americans at the treatment of U.S. captives. Conditions improved after 1969 as the North Vietnamese realized that the harsh treatment of POWs harmed their propaganda efforts. In late 1970 the North Vietnamese finally released an accounting of the men held in captivity.

An ingenious program was designed to keep the prisoner of war issue alive in the minds of the American people. POW identification bracelets were issued with the names of American prisoners on them. These proved to be very popular and at one point sales reached 5,000 per day. President Nixon was accused by some POW families of exploiting the issue to justify the continuance of the war and fifty of them picketed the White House calling for a withdrawal of troops from Vietnam, but in general the POW issue was seen as working against the anti-war movement.

Studies after the war showed that the surviving prisoners, despite the depravation of food and frequent torture in captivity, showed remarkably little psychological or physical problems later in life. One possible explanation for this is that, unlike Korea and World War II, the vast majority of the prisoners in Vietnam were officers who had received some prisoner of war training and were better able to withstand the pressures of captivity. Two former POWs became U.S. Senators (Jeremiah Denton of Alabama and John McCain of Arizona) and another, James Stockdale, ran for vice president with Ross Perot in 1992. In 1996, President Clinton named a former POW, Douglas "Pete" Peterson, as the first U.S. ambassador to Vietnam since the end of the war.

Since taking office, President Nixon had believed that a key to relieving enough of the pressure on South Vietnam for an American withdrawal was to disrupt the steady stream of supplies down the Ho Chi Minh Trail in Laos and Cambodia. Operation Menu, the secret bombing of Cambodia begun early in 1969, had failed to stop the infiltration. The Cambodian leader, Prince Sihanouk, had attempted to play the Americans and the communists off against one another, welcoming American attacks on the communists who were increasing their control of the eastern part of his country, but officially attempting to preserve Cambodian neutrality to avoid retaliation by North Vietnam. After the American bombing of Cambodia had begun in 1969, the North Vietnamese had increased their support of the Khmer Rouge, the Cambodian communist movement, to the point that it had become a serious threat to Sihanouk’s government.

On March 18, 1970, Sihanouk was overthrown by his pro-American Prime Minister Lon Nol. Sihanouk, who was in Moscow appealing to the Soviets to use their influence to restrain the communist incursions into Cambodia, traveled to Beijing where he did a complete flip-flop and announced that he was joining with his former communist enemies to regain power, alleging that the CIA had engineered his overthrow. Cambodia disintegrated into chaos as the Khmer Rouge and North Vietnamese forces pushed further west into Cambodia and South Vietnamese troops (with American support) crossed the border, attacking communist sanctuaries.

Nixon had contemplated a "bold step" against the communists in Cambodia even before Sihanouk’s ouster. The chaos in Cambodia proved to be the pretext for an American invasion and a widening of the war in Southeast Asia. On April 14, Lon Nol appealed for help against the communists. Nixon feared that Cambodia would "go down the drain" without U.S. help. He ordered General Abrams to prepare an invasion plan into the notorious "Fish Hook" region that the U.S. believed contained a major North Vietnamese military command post. On April 30, Nixon announced the invasion to the American people:

As he spoke, an invasion force of 20,000 (15,000 of them American) supported by massive amounts of air power entered Cambodia. Lon Nol, who had not been consulted, denounced the invasion and said that he only wanted military equipment to clear the communists out himself. The invasion lasted two months. The huge communist headquarters was never found. As Secretary of Defense Laird had insisted prior to the invasion, it had never existed as a single entity that could be captured. Large amounts of communist weapons were seized and the military claimed 4,776 Communist dead. U.S. losses were 338 killed, 1,525 wounded. While the Americans withdrew, the South Vietnamese Army continued to push into Cambodia. The fighting created over 200,000 refugees. The communists were able to quickly replace the weapons they had lost with Soviet and Chinese imports.

Nixon had predicted that the invasion of Cambodia would cause "a hell of an uproar" at home. Over 200 college campuses exploded in protest. The morning after the invasion, Nixon had referred to student protesters as "bums." Then, at Kent State University in Ohio, disaster struck. On May 2, students burned the ROTC building, prompting Governor James Rhodes to call out the Ohio National Guard. Rhodes appeared on campus and called the student demonstrators, "worse than the brownshirts and the communist element." Two days after the burning of the building about a thousand students began another demonstration with about two thousand other students watching. The head of the Guard told reporters, "These students are going to have to find out what law and order is all about." Then four students died:

Within a week 405 colleges closed down in protest. On May 9, 100,000 protesters marched in Washington, D.C.. Ten days after the deaths at Kent State, two more students died at Jackson State in Mississippi after a demonstration had turned violent and police fired at a girl’s dormitory. The deaths at Kent State and Jackson State issued in a time of increasing polarization and violence in America over the anti-war movement. The trial of eight anti-war activists accused of inciting a riot in Chicago during the 1968 Democratic Convention turned into a circus with blatantly disrespectful defendants and an openly biased judge. A militant faction of SDS, the Weathermen, advocated an overthrow of the government. During the summer of 1970, a bomb destroyed a building on the University of Wisconsin campus where military research was conducted, killing one and wounding four others.

President Nixon attempted to offset the anti-war movement by secretly sending presidential aide Charles Colson to organize counter-demonstrations. On May 8, fighting broke out between construction workers and anti-war demonstrators in New York City when the demonstrators attempted to lower a flag at City Hall to half-mast in memory of the students killed at Kent State. Two weeks later the Building and Construction Trades Council held a 150,000 person march in the city to demonstrate their support of the invasion.

Proclaiming the invasion "the most successful operation" of the war, Nixon announced on June 3 that he was now able to resume the withdrawal of U.S. troops. Congress did not view the invasion as a success, but rather as merely a further widening of the war. On June 24 the Senate voted 81-10 to repeal the Gulf of Tonkin Resolutions. A week later, the Senate passed the Cooper-Church Amendment barring future use of U.S. military personnel from further use in Laos or Cambodia. The House of Representatives initially rejected this, but a compromise plan was passed in January 1971 that forbid only the use of ground troops in Laos and Cambodia. An effort by Democratic Senator George McGovern and Republican Mark Hatfield to set a December 31, 1971 deadline for the withdrawal of U.S. troops from Vietnam failed, although the Gallup poll showed that 55% of the American people favored its passage.

Despite the turmoil at home, by the end of 1970, there was strong evidence that the war, at least from the American perspective, was beginning to wind down. American personnel in Vietnam had dropped from 536,000 at the end of 1968 to 335,000 by the end of 1970. Casualties were dropping also. 4,221 had been killed in 1970 compared to 9,414 the previous year.

The invasion of Cambodia had stalled both the official and unofficial Paris Peace Talks. In October of 1970, Nixon had proposed a "cease-fire in place," which for the first time raised the possibility that North Vietnamese troops would be allowed to remain in the South. Still, the North Vietnamese rejected this proposal, continuing to demand a total U.S. withdrawal and the removal of President Thieu from power.

As American troops left Vietnam, the U.S. military was increasingly dependent on airstrikes to slow North Vietnamese infiltration down the Ho Chi Minh Trail, which had reached a level of 100,000 men per year after the invasion of Cambodia. As earlier experiences had indicated, air power was ineffective in this task. Barred by Congressional action from using U.S. troops to attack the trail in Laos and Cambodia, the U.S. approved a major South Vietnamese invasion of Laos in February of 1971. This became viewed as a major test of Vietnamization. Code named Lam Son after a fifteenth century Vietnamese victory over the Chinese, the invasion began on February 8 as 17,000 South Vietnamese troops moved west from the reactivated base of Khe Sanh to enter Laos. From the beginning the operation was, in the words of Henry Kissinger, "conceived in doubt and confusion." The U.S. had earlier estimated that such an operation would require 60,000 U.S. troops. Now the South Vietnamese were expected to accomplish it with less than a third of that number. It took the ARVN almost a month to reach their main objective of Tchepone, a major communist supply center, as they suffered 3,000 casualties. Thieu ordered many of his units to halt as a result of the casualties. When a few ARVN units finally arrived, they found that the area had already been destroyed by American air attacks. Dispersed from their base by the air attacks, the North Vietnamese troops encircled the ARVN units and engaged them in a devastating artillery duel. A debacle ensued. By the time the final South Vietnamese troops were rescued in late March, the ARVN had suffered 9,000 casualties, almost 50% of those committed in the attack. The U.S. lost 176 airmen in efforts to rescue the ARVN soldiers during their retreat. Although President Nixon proclaimed that the operation showed that "Vietnamization has succeeded," and Thieu staged a victory parade in Saigon, Kissinger admitted that the operation "had fallen far short of our expectations." One of Kissinger’s aides, General Alexander Haig, concluded that the South Vietnamese Army had been unable to fight effectively without U.S. leadership. Military analyst Brian Jenkins called the invasion "a first rate disaster." The Vietnamese blamed the Americans. Vice President Ky, who had observed the staging of the invasion, had predicted its failure at the onset. "It was a failure because the operation was unnecessary. If you send your troops to make an enclave (fortified area), to draw the communist troops and then destroy them—Yes. But just to go there in that jungle for a promenade (parade)—what for? What for?" Regardless of the blame, Lon Son called the entire premise of Vietnamization into question. Would the South Vietnamese ever be able to defend themselves? Nixon, committed to a pattern of withdrawal and beset by strong public opposition to any delay, had little choice but to continue upon his course, despite the lack of progress in both Vietnamization and the peace negotiations.

Protests against the war continued to increase, frustrating Nixon who believed that they strengthened Hanoi’s will to avoid concessions in the peace negotiations. In April, the Vietnam Veterans Against the War staged a demonstration in Washington, D.C. in which hundreds threw their medals won in Vietnam on the steps of the Capitol. A leader of the veterans, former Navy lieutenant John Kerry, himself a recipient of five major combat medals, told Congress: "Everyday … someone has to give up his life so that the U.S. doesn’t have to admit something that the entire world already knows, so that we can’t say that we have made a mistake. Someone has to die so that President Nixon won’t be, and these are his words, ‘the first President to lose a war.’" In March, public opinion polls showed that support for President Nixon’s policies in Vietnam had dropped to its lowest level since he had entered office (34%). Nixon responded that, "policy in this country is not made by protests."

On June 13, 1971, Nixon received another blow as the New York Times began to publish a secret Defense Department history of the decision-making in the U.S.’s involvement in Vietnam between 1945-1968 that had been commissioned by Secretary of Defense McNamara in 1967. Although the study, dubbed The Pentagon Papers, stopped prior to Nixon’s presidency, it painted an unflattering view of American involvement, revealing for the first time clandestine efforts to violate the 1954 Geneva Agreements, the U.S. role in the overthrow of Diem, and the frequent evidence of the failure of U.S. policies at the same time that the government and military were proclaiming success. The documents had been turned over to Times reporter Neil Sheehan by Daniel Ellsberg, a former Pentagon employee who had volunteered to serve as a civilian pacification advisor in Vietnam. Ellsberg had returned to the Pentagon in 1967 and helped prepare the massive 7,100 page study. Based on his observations in Vietnam and the preparation of the study, Ellsberg became convinced that the war had to be stopped: "When I finished reading the Pentagon Papers I understood at last that the war was one war; there wasn’t a French war followed by a Vietnamese war and an American war—there was one war that we had participated in from the beginning, and it was a war that we never had any right to be in at all, any more than the French did." Ellsberg began to photocopy the documents and gave a set to Senator Fulbright in 1969 in hopes that they would trigger a Senate investigation. When this failed to materialize, he waited until the invasion of Laos to turn them over to Sheehan.

The publication of the Pentagon Papers incensed Nixon for several reasons. He believed that the disclosures would hamper support for his policies and, as Ellsberg had hoped, fuel the anti-war movement. More importantly, Nixon feared that this would encourage, in Kissinger’s words, a "hemorrhage of state secrets." At the time delicate secret negotiations were being held with both the Soviet Union and China and Nixon feared that these secrets would also leak to the press. The government sought an injunction (court order) to prevent the further publication of the Pentagon Papers, but on June 30 the Supreme Court ruled that the government could not prevent their publication. Nixon now became determined to prevent future breaches of security. Presidential assistant John Ehrlichman asked Egil Krough, another White House assistant, to set up a team to plug these leaks. Along with David Young of Kissinger’s National Security staff, Krough formed a group jokingly referred to as "the Plumbers." On July 24, 1971, Nixon met with Krough and told him to find out all he could about Ellsberg and any possible accomplices. The president feared that Ellsberg knew other government secrets and would disclose these also. The FBI was originally given this task, but their investigation yielded little. Krough then told Ehrlichman, "Look, we’re not getting results out of the FBI. I have an ex-FBI and ex-CIA man working for me—I’d like to turn them lose on it." These men were G. Gordon Liddy and E. Howard Hunt who had been employed in the Plumbers unit. Ehrlichman, and later Nixon, agreed. On Labor Day weekend, three Cuban exiles, recruited by Liddy and Hunt, broke in to the office of Ellsberg’s psychiatrist in Los Angeles in a fruitless attempt to find additional information. After this break-in, the Plumbers were disbanded, but the main participants were put to work in other clandestine efforts to damage "enemies" of the president. A year later, in June 1972, Liddy and Hunt, now working for the Committee to Re-elect the President, organized a break-in of the Democratic Party’s headquarters in the Watergate complex in Washington. The effort to plug leaks and discredit the administration’s critics on Vietnam ultimately led to the Watergate Scandal which forced Nixon to resign in August 1974 in the face of near certain impeachment. As his chief of staff, H.R. Haldeman later wrote: "Without the Vietnam war there would have been no Watergate."

Elections were held in South Vietnam in October 1971. President Thieu was challenged by popular Vice President Nguyen Kao Ky, who he had outmaneuvered for the presidency in 1967, and General Duong Van Minh, who had led the coup against Diem in 1963. The U.S. hoped that the elections would provide a demonstration of democracy. Instead they turned into a farce. Ky’s candidacy was thrown out on a technicality by the Supreme Court, which had been appointed by Thieu. Then, accusing Thieu of fraud and vote fixing, Minh withdrew, producing copies of orders issued by Thieu to provincial chiefs instructing them to buy votes and transfer "unfriendly civil servants to other jobs." Under American pressure, the Supreme Court reversed itself, allowing Ky to appear on the ballot, but he too refused to run, claiming that Thieu had rigged the election and accusing the president of being "the principal actor in the farce." Thieu ran unopposed and captured 94% of the vote, the only opposition being registered by voters who mutilated their ballots.

Nixon increasingly came to believe that the only way to end the stalemate in the peace negotiations was to work through North Vietnam’s allies the USSR and China. The North Vietnamese remained insistent that Thieu must go and the U.S. was unwilling to permit North Vietnamese troops to remain in the South, hence little progress had been made in the past year. On July 15, 1971, Nixon announced that he had been invited to visit China in early 1972. Nixon, who had been seen as an extreme opponent of "Red China" throughout his political career, hoped to exploit tensions between the Chinese and the Soviet Union to convince both that agreements with the U.S. were more important than continued support for North Vietnam. The Chinese-Soviet split had been craftily manipulated for years by the North Vietnamese to force both sides to supply them, lest they be labeled as "soft on American imperialism." This competition between the communist powers enabled the North Vietnamese to get the supplies they needed (and at a far greater rate than they could be destroyed by U.S. bombing) without giving either power the ability to control Hanoi’s activities. Nixon’s visit to China frightened the North Vietnamese. They had bitter memories of what they considered China’s "sell-out" of Vietnamese interests at the Geneva Conference in 1954. In 1971, the Chinese counseled Hanoi to modify their demands and allow Thieu to remain in power in the South in order to secure a U.S. withdrawal.

Shortly after Nixon’s visit to China in February 1972, the North Vietnamese launched a major attack across the DMZ. Accompanying attacks were launched in the Central Highlands and across the Cambodian border north of Saigon. The communists attempted to bring the war to closure by dealing the South Vietnamese a crushing defeat, hoping that this would convince the Americans of the failure of Vietnamization and force U.S. concessions in Paris:

Beginning on March 30, the communists committed 120,000 North Vietnamese regulars and thousands of Vietcong guerrillas supported by Soviet artillery, rockets, and tanks to the attack. In the north, South Vietnamese resistance soon collapsed:

This huge communist attack presented the greatest threat to the South since the Tet Offensive; however, unlike 1968, there were few American combat troops to stem the tide. Only 6,000 of the remaining 70,000 U.S. troops were combat troops. A day after the attack began, Nixon ordered a resumption of the bombing of North Vietnam, which had been officially suspended since Johnson’s bombing halt of October 1969. Nixon realized that "all the air power in the world" would not save South Vietnam "if the South Vietnamese aren’t able to hold on the ground," but hoped that the bombing would both strengthen South Vietnamese morale and convince the North Vietnamese that he would use extreme force to prevent the collapse of the Saigon government. After the fall of Quang Tri on May 1, Nixon announced that the U.S. would intensify its air attacks on Hanoi and, for the first time, mine Haiphong harbor. The mining of Haiphong was an attempt to seal of North Vietnam’s main source of supplies from the Soviet Union. The mining of the northern ports raised the possibility of a direct confrontation with the Soviet Union should one of its ships be sunk by an American mine. In announcing the mining, Nixon also repeated the U.S. peace terms that had been outlined in January, offering to withdraw all U.S. troops within four months of the signing of a cease-fire and the return of U.S. prisoners. There was, however, a crucial difference between the terms announced in January and May. In his May 8 speech, Nixon made no mention of the previously key U.S. stipulation that North Vietnam also agree to withdraw its troops from the South.

The decision to mine the northern ports also jeopardized a key summit meeting which had been planned with the Soviets for late May. The two countries had been painstakingly working out a major nuclear arms reduction treaty for over a year and now the summit was in jeopardy. Nixon nervously awaited the Soviet response. When it came, it contained only a mild protest of the mining and a complaint that U.S. bombs in Haiphong harbor had hit a Soviet freighter. By not canceling the summit, the Soviets were signaling that their own desire to reach an arms agreement had a greater priority than support of their North Vietnamese allies. As a Soviet official told reporter Stanley Karnow: "We’ve done a lot for those Vietnamese, but we’re not going to let them spoil our relations with the United States." Nixon’s gamble had worked. With massive U.S. air support, the South Vietnamese forces stiffened and the communist attack was turned back. The communists suffered approximately 50,000 deaths in their Easter Offensive, but once again demonstrated their will to incur enormous casualties in the face of superior firepower. As Nixon wrote in his diary, "The real problem is that the enemy is willing to sacrifice in order to win, while the South Vietnamese simply aren’t willing to pay that much of a price in order to avoid losing."

By the summer of 1972 both sides had new motivation to bring the conflict to an end. 1972 was an election year and Nixon in his 1968 campaign had said, "those who have had a chance for four years and could not produce peace should not be given another chance." In the Democratic primaries, Senator George McGovern, a long-time critic of the war had emerged as the Democrats’ likely presidential nominee. Vietnam would undoubtedly be a major issue in the campaign. Nixon also realized that congressional action was moving steadily to end authorization for the use of U.S. forces in Vietnam. When the Senate passed a resolution in July requiring a total U.S. withdrawal, contingent only on the return of U.S. prisoners, Kissinger feared that the communists only had to delay until, "Congress voted us out of the war." The North Vietnamese also had reason to compromise. Their latest military effort had failed to achieve the breakthrough that they had hoped for and they now feared that their allies, China and the USSR, would abandon them. More importantly, they now had hope that the U.S. would no longer insist on a withdrawal of all North Vietnamese troops from the South. Nixon had omitted any reference to a mutual withdrawal in his May 8 speech and as early as May 1971 the U.S. had hinted at a military cease-fire that would leave negotiations as to a political settlement to the governments of North and South Vietnam. The point in contention now only seemed to be the North’s insistence on the removal of the Thieu government in the South.

On October 8, 1972, North Vietnam’s Le Duc Tho met with Kissinger in a private home in Paris. There the North Vietnamese offered, in their words, "a very realistic and simple proposal." The U.S. and the North Vietnamese would arrange a cease-fire and prisoner exchange in return for an American withdrawal. A "council of national reconciliation," composed of all Vietnamese political elements, would then work out a permanent peace and eventually supervise national elections in the South. Thieu would remain in power and North Vietnamese forces would remain in the South. Both sides had now given up their major demand that had hamstrung the negotiations for four years. As Kissinger said, a North Vietnamese withdrawal from the South had been "unobtainable through ten years of war. We could not make it a condition for a final settlement." It took the negotiators ten days to work out the details, and on October 18, Kissinger took the agreement to President Thieu, who had not been consulted about the terms. Thieu angrily rejected the terms:

Thieu demanded that the terms be reworked to recognize the sovereignty of South Vietnam and that all North Vietnamese troops be withdrawn north of the DMZ. Nixon cabled Thieu and threatened to cut off all U.S. assistance to South Vietnam and negotiate a separate treaty with the North Vietnamese. On October 24, Thieu publicly denounced the agreement. Trying to force the Americans’ hand, Hanoi announced the terms of the agreement and their approval two days later. Despite Saigon’s objections, the same day as Hanoi’s announcement Kissinger held a press conference at the White House and proclaimed "peace is at hand." Although Nixon cautioned that there were "differences that must be resolved," and asked North Vietnam for a delay, it finally appeared to Americans that the county’s long involvement in Vietnam was finally drawing to a close. On November 7, Nixon trounced McGovern 61% to 38%, failing only to carry Massachusetts and the District of Columbia in the largest electoral landslide in American history (520-17).

Despite Nixon’s landslide and Kissinger’s pronouncement of "peace is at hand," closing the negotiations in Paris proved to be impossible. In order to placate Thieu, the U.S. returned with a list of modifications to the agreement. Hanoi responded with their own amendments. Soon the negotiations deadlocked. John Negroponte, who had served as a negotiator in Paris and was now a member of the National Security Council, believed that the North Vietnamese feared a double-cross. "Hanoi was fearful that it had become victim to the biggest con job in history and that the U.S. had promised to go through with a peace treaty just for domestic purposes and that once the election was over there was a danger that the United States might renege on its promise." To reassure Thieu of continued U.S. support, the U.S. now promised a major increase in military supplies and economic aid and immediately began deliveries. Negroponte believes that, by December, some of Hanoi’s leaders began to doubt the wisdom of the settlement. A Kissinger aide, William Lord, agreed, "… in December it was clear that the North Vietnamese were sliding away from an agreement. Every time we would get close, they would slide in new conditions. It was clear that they were playing on public opinion, undercutting us at home and stonewalling us in Paris, and there was no choice but to break off the negotiations." On December 13, the negotiations collapsed as Le Duc Tho returned to Hanoi. Nixon now feared that a settlement would not be reached until the new Congress convened in January. Ever fearful that Congress would mandate an end to American involvement, Nixon now acted to force the negotiations to resume and to demonstrate to Thieu that he would not be abandoned upon the removal of U.S. forces.

On December 18, 1972, the United States began the largest bombing campaign of the war. Focusing on Hanoi and Haiphong, for eleven days B-52s hammered North Vietnam. 100,000 bombs were dropped on the two cities, equivalent to five atomic bombs of the size used on Japan. Despite efforts to avoid civilian targets, the massive bombing effort devastated several residential neighborhoods and a major hospital. In the raids, the U.S. lost 26 aircraft, including fifteen B-52s (at a cost of $8 million each). Forty-two airmen died and another 31 were captured. Condemnation of the Christmas Bombing (lasting from December 18 through December 30, with a one day pause for Christmas) was strong both within the U.S. and abroad. The New York Times accused Nixon of reverting to "Stone Age barbarism" and stated that: "Civilized man will be horrified." The Times of London stated that the bombing "is not the conduct of a man who wants peace very badly." The Pope told an audience at the Vatican that the bombing was causing him "daily grief." Even loyal Republican supporters had doubts. Ohio Senator William Saxbe told reporters: "I have followed President Nixon through all his convolutions [twists] and specious [misleading] arguments, but he appears to have left his senses on this." After the Americans had exhausted their targets and the North Vietnamese had nearly run out of Surface to Air Missiles, the two sides returned to the negotiating table in Paris.

Following two days of negotiations, the two sides reached an agreement on January 9, 1973. The terms were essentially the same that Kissinger had taken to Thieu in October. Nixon had warned him after the bombing had stopped: "You must decide now whether you desire to continue our alliance or whether you want me to seek a settlement with the enemy which serves U.S. interests alone." A major purpose of the bombing had been to reassure Thieu of American support should the communists violate the agreement. Kissinger aide, Lord explained: "The President felt that he had to demonstrate that we couldn’t be trifled with—and frankly, to demonstrate our toughness to Thieu—this was the rationale for the bombing." After the renegotiation led to an agreement, Thieu had little choice. Nixon wrote to him on January 14 that he intended to sign the agreement regardless of any further objections: "I will do so, if necessary, alone. In that case I shall have to explain publicly that your Government obstructs peace. The result will be an inevitable and immediate termination of U.S. economic and military assistance…" Thieu later said, "How could I not accept the peace agreement? How could I continue to fight—with what?" Nixon did assure Thieu of continued military equipment and the use of bombing should North Vietnam break the peace agreement and mount an invasion. Ambassador Ellsworth Bunker delivered handwritten assurances to Thieu: "He received assurances—which I gave him personally—written assurances from the President that in case of a violation of the Paris agreement by the other side we would come to their [South Vietnam’s] assistance."

The agreement, known as the Paris Peace Accords, was formally signed on January 23, 1973. In a televised address, Nixon proclaimed that "peace with honor" had been achieved:

The cease-fire took effect on January 27. Later that day, Secretary of Defense Laird announced the end of the draft and the beginning of the all-volunteer armed forces. American POWs were released and American forces came home, leaving only a token force of advisors in Saigon. Many criticized the peace terms. Thieu called them a "betrayal." Others accused Nixon of arraigning a cynical peace that he knew would soon collapse, burying the Saigon government. Anti-war activists maintained that the terms Nixon agreed to could have been obtained in 1968 or 1969 and that the last four years of the war had been fought for nothing other than Nixon’s refusal to admit defeat. Over 56,000 Americans died in Vietnam and, especially in its last five years, the war had torn American society apart. Kissinger and Le Duc Tho were awarded the Nobel Peace Prize for the negotiations that brought the war to a close. Kissinger accepted the award. Le Duc Tho refused, maintaining that peace would not come to Vietnam until it was united.

At 11:00 a.m. on April 30, 1975, a single North Vietnamese tank smashed through the half-open gates of Saigon’s presidential palace. A lone soldier raced toward the balcony and planted the Vietcong flag. After thirty years, the battle for Vietnam was finally over. South Vietnam had lasted just two years after the final American withdrawal in 1973.

After the signing of the Paris Peace Accords in January 1973, Congress had moved swiftly to regain more control over foreign affairs and prevent a reoccurrence of the events that had allowed the war in Vietnam to grow far beyond the authorization most intended in the Gulf of Tonkin Resolutions. In July 1973, Congress voted to cut off funds for any further U.S. military action in Southeast Asia. Even after the withdrawal from Vietnam, U.S. planes had continued to bomb Khmer Rouge targets in Cambodia as Lon Nol’s government was rapidly losing ground to the communists. The congressional action brought the Cambodian bombing to a halt. Far more significantly, in November, Congress overrode the president’s veto to pass the War Powers Act, which severely limited the president’s power to commit troops overseas without congressional approval. The Act required the president to notify Congress immediately if troops were committed to an overseas conflict and secure congressional approval within sixty days:

The Congress also cut back presidential requests for aid to South Vietnam. In 1974, Congress set a $1 billion limit (later scaled back to $700 million) to aid to the Thieu government, a drastic drop from the $30 billion in aid South Vietnam had received during the early 1970s. Billions of dollars of high technology military equipment had been rushed to South Vietnam prior to the signing of the peace agreement, but in many cases the South Vietnamese received little or no training on its use. Other factors tended to weaken U.S. support for South Vietnam. By the middle of 1974, President Nixon was severely wounded by the Watergate Scandal as the summer’s television schedule was dominated by congressional hearings, which exposed ever-increasing evidence of criminal wrongdoing on the part of key White House aides. In the fall, huge amounts of U.S. military equipment were rushed to Israel during the Yom Kippur War. Its replacement had a higher priority than the replacement of material for the South Vietnamese Army. In addition, the Arab oil embargo caused a dramatic rise in prices worldwide, curtailing the buying power or U.S. aid.

Even after the U.S. withdrawal in the spring of 1973, the military situation in South Vietnam appeared to favor the Thieu government. Although 150,000 North Vietnamese troops had been allowed to remain in the South, they were outnumbered by the ARVN by a margin of over 6:1. In addition, the Saigon government controlled 75% of South Vietnam’s land and 85% of its people. In late 1973, President Thieu attempted to utilize this numerical superiority and clear the communist forces out of the rich Mekong Delta region. Heavy fighting ensued for months. Initially the ARVN was able to take considerable territory from the communists as the communist forces had attempted to regroup and resupply after the armistice; however, by mid summer the communists had regained most of the lost territories and ARVN casualties exceeded 1,000 per month. After turning back Thieu’s attack, the communists concentrated on building the infrastructure (physical foundation) for a final attack on South Vietnam. The Ho Chi Minh Trail was modernized and an all-weather highway was created that stretched all the way to the Mekong Delta. In addition, a three thousand mile oil pipeline was built that allowed oil supplies to reach communist forces within 100 miles of Saigon. With this massive construction, the North Vietnamese were betting that the B-52s would never return, despite Nixon’s promises to Thieu in January 1973.

In addition to the crumbling military situation, the American withdrawal and the world-wide inflation caused by the oil embargo had severely weakened the South Vietnamese economy. Prior to 1973, the refugees crammed into South Vietnam’s major cities had largely been able to support themselves by catering to American servicemen. These jobs had gone with the Americans. There was little industry or commerce in South Vietnam to pick up the slack. Military morale began to erode when the government was unable to ensure that the soldiers were paid. A 1974, U.S. study showed that 90% of the ARVN were not receiving enough pay to support their families. Inflation and declining U.S. support accounted for part of this problem, but so did the high level of corruption present in South Vietnamese society. Commanders often took a cut of the payrolls and demanded that the soldiers pay for their rations and ammunition.

In the fall of 1974, the communists began to plan their final offensive. Nixon’s resignation in August had convinced them that the U.S. would do little to prop up Thieu’s government and by now North Vietnam possessed the world’s fifth largest army. The first move was an attack on Phuoc Long Province less than 100 miles north of Saigon in January 1974. The attack had two purposes: it provided a test to judge the U.S. response to an outright violation of the Paris Peace Agreement and, if successful, would provide the North Vietnamese with a staging area for the final assault on the South. The communists succeeded in both objectives. The B-52s did not return, and the U.S. made only a formal protest of the violation of the peace agreement. Within three weeks, the provincial capital of Phouc Binh had fallen. With a staging area secured, the North Vietnamese began to assemble men and material for a spring offensive. Its overall commander, General Van Tien Dung, secretly entered the South, completing the long journey on bicycle disguised as a peasant. Everything was now in place for the final attack.

The South Vietnamese had assumed that the communist attack would come from the north and concentrated their troops in the provinces close to the partition line. Instead, the communist chose to drive a wedge between the ARVN forces, attacking in the Central Highlands at Ban Me Thout. The attack began on March 10. Within five days, South Vietnam was in collapse as communist forces thrust eastward toward the coast, virtually cutting the South in half. In an effort to consolidate his forces for a defense of Saigon, Thieu ordered the entire Central Highlands abandoned. This triggered a mass panic as soldiers and civilians streamed toward the coast to avoid the invading forces. Over a million people eventually joined this "Convoy of Tears." Meanwhile, the North Vietnamese forces turned north to surround Da Nang and Hué. Hué fell on March 25, Da Nang five days later. On April 1, the New York Times reported: "The North Vietnamese are surging through the country and meeting only sporadic resistance; territory is being taken by virtual default." Originally planned as up to a two-year assault, the North Vietnamese now revised their timetable and set as a goal the capture of Saigon on Ho Chi Minh’s birthday, May 19.

By the second week of April communist forces had swept to within fifty miles of Saigon. Spirited resistance by ARVN forces held off the assault for twelve days at Xuan Loc, only 38 miles from Saigon, before surrendering on April 21. The same day, under American urging, President Thieu resigned. Thieu left, bitterly accusing the U.S. of betrayal: "They abandoned us. They sold us out. They stabbed us in the back. It is true—they betrayed us. A great ally failed a small ally." President Ford declared two days later that there would be no more American aid. "Today America can regain a sense of pride that existed before Vietnam. But it cannot be achieved by refighting a war that is finished as far as America is concerned."

With North Vietnamese forces at the gates of Saigon, the only question remaining for the Americans was the evacuation of its few remaining forces in Vietnam and as many of the 140,000 South Vietnamese who were listed on the embassy’s endangered list. Forty ships, including three aircraft carriers, rendezvoused off the coast as huge Ch-53 helicopters awaited orders to begin America’s final withdrawal. On April 30, Bing Crosby’s "I’m Dreaming of a White Christmas" was broadcast over the U.S. Armed Services radio. It was the code for the evacuation. Helicopters dispatched 130 Marines at the U.S. Embassy compound to provide security for the airlift. South Vietnamese besieged the embassy, pleading for evacuation, but only a few could be accommodated. The airlift began in the afternoon as helicopters landed and took off from the embassy’s roof amidst intermediate communist shelling which killed two marines. As the helicopters returned to the evacuation ships, they saw unauthorized helicopters piloted by South Vietnamese officers clogging the landing areas. Their $250,000 machines were pushed overboard, "discarded like pop-top beer cans," to make room for more landings. In total, 7,000 Americans and Vietnamese were evacuated on April 29, joining 120,000 other South Vietnamese who had fled in the last weeks of the Saigon government. At 7:53 a.m. on April 30, the last eleven U.S. Marines left the embassy with a carefully wrapped American flag. After thirty years, the American fight against communism in Vietnam had finally come to an end. A few hours later, General Duong Van Minh ordered the surrender of all ARVN forces, finally bringing to an end the war that had begun in 1945.