Vietnam War

The Vietnam War was an international Cold War conflict for control of South Vietnam involving North Vietnam and its allies against South Vietnam, the United States, and their allies between 1962 and 1975. While there had been earlier, noncombat involvement of the United States before 1962, the Vietnam War, in terms of U.S. combat, began in 1962 with direct support to the South Vietnamese Army of the Republic of Viet Nam (ARVN), with the last U.S. bombing of North Vietnam in late 1972. At various times, the U.S. and ARVN forces were joined by South Korean, Filipino, New Zealand, Thai and Australian troops.

The principal opposition was the North Vietnamese People's Army of Viet Nam (PAVN) and the Viet Cong (VC) military wing of the National Front for the Liberation of South Vietnam (NLF). The Vietnam War fits into the context of the Wars of Vietnam, with Western involvement beginning in the 19th century CE, and wars between Vietnam and China beginning in the 1st century, with a final regional peace treaty for the Third Indochina War in 1999.

In the West, the 1962-1975 "Vietnam War" is primarily considered as a part of the Cold War. Before that, there were wars of colonialism and nationalist resistance to it. Colonialism was not limited to the Third French Republic, but to a long history of Chinese attempts to control the region. Vietnamese nationalism is not something new, but unfortunately this was often not realized in other countries.

This article focuses on the combat involvement of the United States, 1962-1972. Details of U.S. politics and opinion that affected it are in Vietnam, war, and the United States. U.S. advisers had been present in the South since 1955, but they began to accompany South Vietnamese combat troops in 1962. The Gulf of Tonkin incident in 1964 signaled the beginning of overt combat involvement, although the overt part was initially limited to air attacks and local security for air bases in the South. In the short term, U.S. air attacks on the North exclusively came from aircraft carriers in international waters.

Major introductions of U.S. ground combat troops came in 1965, generally increasing until 1968, when the policy of Vietnamization went into effect. As Vietnamization went into effect, and the Paris Peace Talks completed in 1972, the U.S. role changed again South Vietnam fought its own ground war, with U.S. ground combat troops withdrawing between 1968 and 1972, with the last air attacks in 1972. After that, the U.S. provided limited replacements of supplies, and maintained a large, diplomatic Defense Attache Office that monitored the RVN until the fall of South Vietnam in 1975.

After the U.S. withdrawal, South Vietnam collapsed after being invaded by the DRV in 1975. Memorable pictures of desperate people clinging to helicopters at the U.S. Embassy reflect the evacuation of diplomatic, military, and intelligence personnel, and some Vietnamese allies. Other than for the immediate security of the evacuation, no U.S. combat troops or aircraft had been in South Vietnam since 60 days after the signing of the peace treaty in Paris.



Vietnam's climate has a major effect on warfare, especially involving vehicles and aircraft. Major operations usually took place in the dry season. While the most southern parts tend to have a generally tropical climate, there are two major climactic periods:
 * Monsoon season of heat, rain, and mud, with limited mobility (May to September)
 * Warm and dry conditions (October to March)

U.S. replaces France
After the Geneva accords of 1954 split the former French Indochina into the Republic of Vietnam (South) and Democratic Republic of Vietnam (North), France no longer had colonial authority. After certain procedural matters were resolved in early 1955, the United States took up a major role in training and funding what was now the Army of the Republic of Vietnam in the South. U.S. intelligence collection personnel had been in the area since the latter part of the Second World War. In 1954, Edward Lansdale, a U.S. Air Force officer seconded to the Central Intelligence Agency, came to Saigon under the cover of Assistant Air Attache leading the Saigon Military Mission, which was a CIA operation whose immediate activities included sending Vietnamese personnel north, to set up stay-behind intelligence collection and covert action teams for future use.

The strategic balance
While Vietnamese Communists had long had aims to control the whole of Vietnam, the specific decision to conquer the South was made, by the Northern leadership, in May 1959. The Communist side had clearly defined political objectives, and a grand strategy to achieve them; there was a clear relationship between long-term goals and short-term actions, within their strategic theory of dau trinh. Some of their actions may seem to be from Maoist and other models, but they have some unique concepts that are not always obvious.

Apart from its internal problems, South Vietnam faced difficult military challenges. On the one hand, there was a threat of a conventional, cross-border strike from the North, reminiscent of the Korean War. In the 1950s, the U.S. advisors focused on building a "mirror image" of the U.S. Army, designed to meet and defeat a conventional invasion. Ironically, while the lack of counterguerilla forces threatened the South for many years, the last two blows were Korea-style invasions. With U.S. air support, the South were able to largely repel a conventional invasion by North Vietnam. The 1975 invasion which defeated the South was not opposed by U.S. forces.

Early U.S. noncombat advisory & support roles
Harry S. Truman, as soon as the Second World War ended, was under great pressure to return the country to normal civilian conditions, and he demobilised rapidly to release funds for domestic spending. There were no such pressures to demobilize, however, on Josef Stalin and Mao Tse Tung. Truman has been blamed for "losing" Eastern Europe and China, but it is less clear what could have been done to stop it. The decision to cut military commitment came home to roost in the Korean War, when Truman had few forces to dispatch.

From 1955, the U.S. took over the role of training and signficantly funding the Southern Army of the Republic of Viet Nam (ARVN). In 1959, the first U.S. advisers to go into combat in the area were in Laos, not Vietnam. With a negotiated settlement to the Laotian civil war in 1962, U.S. attention shifted to South Vietnam. Communications intercepts in 1959, for example, confirmed the start of the Ho Chi Minh trail and other preparation for large-scale fighting. This information may not have been fully shared with the South Vietnamese, due to security concerns over the intelligence methods used to get the information.

Interactions of South Vietnamese & U.S. politics
After the French colonial authority ended, Vietnam was ruled by a nominally civilian government, led by first Bao Dai and then, from 1954, by Ngo Dinh Diem; neither were elected. Communist statements frequently spoke of it as a U.S. "puppet" government, although the Northern government had not been elected and had little more claim to democratic legitimacy. Both governments were clients of the different major sides in the Cold War.

Diem was strongly anti-communist, but authoritarian, and there were increasing protests against his rule. He was a Catholic in a Buddhist-majority country, but gave preference to Catholics. While personally ascetic, he tolerated a serious level of corruption in the government.

Effect on military efficiency
Not only under Diem, appointing officers to the command of military units, and also to posts in the separate hierarchy of district and province chiefs, often were made as political loyalty as the first criterion, possibly bribes or favors at the next, and military proficiency sometimes as a last consideration. Officers were shifted from post to post, in the interest of breaking up potential coup plots.

In practice, the most powerful military positions were the commanders of the four Corps tactical zones (CTZ), also known as military regions. Even though a CTZ was geographic, and province and district chiefs were usually military officers, the province/district reporting went through the Ministry of the Interior rather than the military Joint General Staff.

Especially powerful units might, in the interest of interfering with coups, be shifted from one chain of command for another. At the Battle of Ap Bac, for example, the potent armored personnel carriers (APC) had been shifted from the operational control of the military commander to that of the province chief. Before the unit commander would commit his resources to battle, at the urging of a U.S. adviser to the division commander, the commanding officer of the APC company had to obtain province chief as well as military approval, significantly changing the

Conflicting goals
Vietnamese and U.S. goals were also not always in complete agreement. Until 1969, the U.S.A. was generally anything opposed to any policy, nationalist or not, which might lead to the South Vietnamese becoming neutralist rather than anticommunist. There is evidence that the U.S. supported attempts to replace governments that were considering forming a neutralist coalition that might include the National Front for the Liberation of South Vietnam, a communist-dominated opposition. The Cold War containment policy was in force through the Eisenhower, Kennedy, and Johnson Administrations, while the Nixon administration supported a more multipolar model of detente.

While there were still power struggles and internal corruption, there was much more stability between 1967 and 1975. Still, the South Vietnamese government did not enjoy either widespread popular support, or even an enforced social model of a Communist state. It is much easier to disrupt a state without common popular or decisionmaker goals.

Instability
The association of the U.S. with the RVN government, however, was sufficiently strong that instability there both reflected adversely on the U.S. role, and seen as interfering with the fight against Communism. While Diem ruled between 1954 and 1963; there followed a period of frequent changes of government, some lasting only weeks, between 1964 and 1967, until moderate stability came in 1967.

Protests generally called the Buddhist crisis of 1963, which also involved other Vietnamese sects, such as the Cao Dai and Hoa Hao, were a major disruption by June. These protests were seen by the U.S. as strengthening the Communist insurgency, and, after rejecting earlier initiatives for a military coup, agreed that Diem had to go.

In November 1963, Diem was overthrown and killed in a military coup. The United States was aware of the coup preparations and, through CIA officer Lucien Conein, had given limited financial support to the generals involved. There is no evidence that the U.S. expected Diem, and his brother and closest political adviser, Ngo Dinh Nhu to be killed; U.S. Ambassador Henry Cabot Lodge Jr. had offered him physical protection.

The leaders of the November coup were replaced by a nominal civilian government really under military control, which was overthrown by yet another military coup (involving some of the same generals) in January 1964.

Between 1964 and 1967 there was a constant struggle for power in South Vietnem, and not just from within the military. Several Buddhist and other factions often derived from religious sects, which became involved in the jockeying for political power, such as the Cao Dai and Hoa Hao. Even the Vietnamese Buddhists were not monolithic, and had their own internal struggles. At varying times, sects, organized crime syndicates such as the Binh Xuyen, and individual provincial leaders had paramilitary groups that affected the political process; while the Montagnard ethnic groups wanted autonomy for their region. William Colby (then chief of the Central Intelligence Agency Far Eastern Division) observed that civilian politicians "divided and sub-divided into a tangle of contesting ambititions and claims and claims to power and participation in the government." Some of these factions sought political power or wealth, while others sought to avoid domination by other groups (Catholic vs Buddhist in the Diem Coup).

After a period of overt military government, there was a gradual transition to at least the appearance of democratic government, but South Vietnam neither developed a true popular government, nor rooted out the corruption that caused a lack of support.

Covert operations
Well before the Gulf of Tonkin and overt operations, there were a number of covert operations, some ostensibly with U.S. advisers to South Vietnamese crews, and some, especially in Laos, of which no public announcement was made. Certain of these operations became public in postwar historical analyses, official announcements at the time, or press reporting that eventually was confirmed.

Regional activity before South Vietnamese independence
Still, there was U.S. activity in Southeast Asia, which grew out of covert operations directed more at China. In August 1950, the CIA bought the assets of Civil Air Transport (CAT), an airline founded after the Second World War by Gen. Claire L. Chennault and Whiting Willauer. While CAT continued commercial operations, it acted as a CIA "proprietary", or covert support organization under commercial cover. CAT aircraft, for example, dropped personnel and supplies over mainland China during the Korean War. CAT later became part of Air America.

When Dwight D. Eisenhower succeeded Truman as President in 1952, after a campaign that had attacked Truman's "weaknesses" against communism and in Korea, he formulated a strong policy of containing Communism. There was much sensitivity over "softness" exemplified by the excesses of Senator Joe McCarthy. While the Eisenhower Administration avoided becoming too enmeshed in the French problem of the Indochinese revolution, airlift was provided by CAT pilots. U.S. Air Force C-119 Flying Boxcar transports, repainted with French insignia. CAT trained the crews at Clark Air Force base in the Phillipines, and then flew the aircraft to Gia Lam Airport in Hanoi. They made airdrops to French forces in Laos between May and July. Eventually, CAT flew logistics missions to Dien Bien Phu, in March to May 1954; one aircraft was shot down and others damaged.

Laos
After France left the region, the Royal Lao Government (RLG) quietly asked the United States to replace the former French funding of the Lao military, and to add military technical aid from the increasingly active Communist insurgency, the Pathet Lao. This assistance started in January 1955, directed by a new part of the Embassy, with the nondescript name Program Evaluation Office (PEO). At first, the PEO simply dispensed funds, but took on a much larger role in 1959.

When the first direct military assistance began in July 1959, the PEO was operated by the U.S. Central Intelligence Agency using military personnel acting as civilians. CIA sent a unit from United States Army Special Forces, who arrived on the CIA proprietary airline Air America, wearing civilian clothes and having no obvious US connection. These soldiers led Meo and Hmong tribesmen against Communist forces. The covert program was called Operation Hotfoot. At the US Embassy, BG John Heintges was designated the head of the PEO.

In April 1961, Chief of Staff of the Air Force Curtis LeMay’s began to approve certain covert operations, such as JUNGLE JIM. He denied them to the press. They were, however, a response to President Kennedy's challenge for the military to develop a force capable of fighting the “Communist revolutionary warfare”, regarded as proxy wars for the U.S. and Soviet Union. One of the first to respond to the call for combat control volunteers

CIA, MACV-SOG and OPPLAN34A
John F. Kennedy approved, on May 11, 1961, a Central Intelligence Agency plan for covert operations against North Vietnam. These included ground, air, and naval operations. Eventually, the operations were transferred to officially military control, in a unit, MACV-SOG, principally reporting to MACV but with an approval chain that often ran to the White House.

CIA naval operations, under Tucker Gougelmann, in 1961, starting with motorized junks. The first motor torpedo boats were transfered to CIA in October 1962. At the end of 1962, raids began.

They received their improved Norwegian Nasty-class boats in 1963. These more sophisicated craft were crewed by Norwegian and German mercenaries as well as South Vietnames; U.S. Navy SEALs conducted the training in Danang. MACV-SOG was formed in January 1964, and took over the "modest" CIA maritime operation, based in Danang, now given the cover name Naval Advisory Detachment, actually branch OP37 of MACV-SOG. The attacks, under the command of MACV-SOG, were actually carried out by the Coastal Security Service of the RVN Strategic Technical Directorate.

So, at least a year before the Gulf of Tonkin, there had been some raids against North Vietnam. Independent of MACV-SOG, the U.S. Navy began to conduct signals intelligence patrols for the National Security Agency, close to North Vietnam but in international waters. These were called the DESOTO patrols, and used overt U.S. Navy destroyers, with a van packed with electronics and technicians mounted on their decks.

On the night of July 30, 1964, four MACV-SOG boats shelled North Vietnamese shore installations, after a series of earlier maritime operations. The North Vietnamese went on high naval alert.

On July 31, 1964, there was a DESOTO patrol. The timing after the MACV-SOG operation may have been coincidental, although there have been suggestions that the increased North Vietnamese activity was a rich environment for SIGINT collection. There is no strong indication that the DESOTO patrols were trying to provoke North Vietnamese response; they carefully stayed in international waters and were fully identifiable as U.S. ships.

U.S. buildup and overt combat involvement
This section focuses on the period when U.S. forces became involved in large-scale, direct combat. Wherever possible, the national-level decisions that went into a change of military action will be presented, but, in a number of situations, an action may have been the result of a perceived need to "do something" rather than having a direct effect on the enemy. Such decisionmaking style is not unique to this period. George Kennan, considered a consummate diplomat and diplomatic theorist, observed that American leaders, starting with the 1899-1900 "Open Door" policy to China, have a neurotic self-consciousness and introversion, the tendency to make statements and take actions with regard not to their effect on the international scene byt rather to their effect on those echelons of American opinion, congressional opinion first and foremost, to which the respect statesmen are anxious to appeal. The question became not: How effective is what I am doing in terms of the impact it makes on our world environment? but rather: how do I look, in the mirror of American domestic opinon, as I do it?

Even when leaders' goals are sincere, the need to be seen as doing the popular thing can become counterproductive. There were many times, in the seemingly inexorable advance of decades of American involvement in Southeast Asia, where reflection might have led to caution. Instead, the need to be seen as active, as well as the clashes of strong egos, separate the needs of policy from the dictates of politics. The personalities of different Presidents and key advisers all had an effect. Many, but by no means all, of the key political decisions were under Johnson, but Presidents from Truman through Ford all had roles.

Although Americans died in supporting South Vietnamese involvement beginning in 1962, the greatest U.S. involvement was from mid-1964 through 1972. U.S ground troops began reducing in 1968 and much more sharply in 1969. So, much of the detailed U.S. political action with other countries will be in Joint warfare in South Vietnam 1964-1968, Vietnamization, and air operations against North Vietnam.

Combat support advisory phase
John F. Kennedy and his key staff, came from a different elite than that which had spawned the Cold Warriors of the Eisenhower Administration. While the form was different, a militant anti-Communism was underneath many of the Kennedy Administration policies. Its rougher operatives had a different style than Joe McCarthy, but it is sometimes forgotten that Robert Kennedy (RFK) had been on McCarthy's staff.

Where Republicans during the Truman and Eisenhower administrations blamed Democrats who had "lost China", the Kennedy Administration was not out to lose anything. The first covert operations in the region began in the Eisenhower Administration, but Kennedy increased both operations in Laos and Vietnam.

Intensification
Guerilla attacks increased in the early 1960s, at the same time as the new John F. Kennedy administration made Presidential decisions to increase its influence. Diem, as other powers were deciding their policies, was facing disorganized attacks and internal political dissent. There were conflicts between the government, dominated by minority Northern Catholics, and both the majority Buddhists and minorities such as the Montagnards, Cao Dai, and Hoa Hao. These conflicts were exploited, initially at the level of propaganda and recruiting, by stay-behind Viet Minh receiving orders from the North.

U.S. personnel went into the field with ARVN personnel starting in 1962. The term "adviser" was popular but not always accurate. While many U.S. personnel indeed did advise their counterparts, and U.S. forces did not take a direct combat role, a substantial part of field activity was devoted to tactical airlift of ARVN troops, and a wide range of technical support. The first American soldier to die in combat was not with ARVN infantry, but part of a signals intelligence team, doing direction finding on Viet Cong radio transmitters in the field, whose team was ambushed.

Th Battle of Ap Bac, fought on January 2, 1963, did involve both U.S. advisers to ARVN commanders, as well as U.S. aviation support. John Paul Vann was the senior tactical adviser, and his outrage about ARVN performance both stimulated aggressive investigative journalism, as well as infuriating the U.S. command.

Deterioration and reassessment
By November 1963, after Diem was killed, there was mixed feelings among the JCS if covert operations alone could have a significant effect. Chief of Staff of the Air Force GEN Curtis LeMay pushed his JCS clleagues for "more resolute, overt military actions." He was joined by Commandant of the Marine Corps GEN David Shoup, and gained stronger support from the Army and Navy chiefs, GEN Earle Wheeler and ADM David McDonald. ADM Harry Felt, commander of United States Pacific Command, also believed covert actions alone would not be decisive. LeMay said "we in the military felt we were not in the decision-making process at all [Chairman of the JCS Maxwell] Taylor might have been but we didn't agree with Taylor in most cases."

To senior civilian officials, with the Joint Chiefs receiving it via Secretary of Defense McNamara, Johnson stated his policy decision in classified National Security Action Memorandum (NSAM) 273, of November 26, 1963. The key point was the U.S. goal was to strengthen South Vietnam to win its own contest; the U.S. expected to begin to withdraw troops. "It remains the central object of the United States in South Vietnam to assist the people and Government of that country to win their contest against the externally directed and supported Communist conspiracy. The test of all U.S. decisions and actions in this area should be the effectiveness of their contribution to this purpose.

He made pacification of the Mekong Delta the highest priority, but also ordered planning for increased yet deniable activity against North Vietnam. "With respect to Laos, a plan should be developed and submitted for approval by higher authority for military operations up to a line up to 50 kilometers inside Laos, together with political plans for minimizing the international hazards of such an enterprise." These operations would change from CIA to MACV control. A "favorable influence", but no operations in, Cambodia was desired.

A high priority was producing "as strong and persuasive a case as possible to demonstrate to the world the degree to which the Viet Cong is controlled, sustained and supplied from Hanoi, through Laos and other channels."

The JCS responded to NSAM 273 with a January 22, 1964 memorandum to McNamara. Significant differences with the Presidential decision, which emphasized assisting South Vietnam, was a JCS goal of "victory" as the goal of U.S. military operations.

Gulf of Tonkin incident
On August 2, it was a DESOTO Patrol destroyer that was believed to have been approached, and possibly fired upon, by the North Vietnamese. After much declassification and study, much of the incident remains shrouded in what Clausewitz has called the "fog of war", but questions have been raised about whether the North Vietnamese believed they were under attack, about who fired the first shots, and, indeed, if there was a true attack. There has not been a clear indication from the North Vietnamese if they thought the DESOTO and 34A operations were part of the same programs, and, if so, if destroyer-sized vessels represented an escalation. Later on the 2nd, the Chairman of the Joint Chiefs of Staff, Maxwell Taylor, ordered that DESOTO patrols should not be made at the same time as 34A operations.

There is more question if the second patrol, reinforced to two ships with air cover, was actually attacked, or if there were merely North Vietnamese warships in their area. Declassified NSA intercepts of North Vietnamese communications, on the 4th, show considerable confusion on the DRV side. Operating under Presidential authority, Johnson launched Operation PIERCE ARROW, air strikes were sent against North Vietnamese naval facilities and the oil refinery at Vinh. attacks on the evening (Washington time) of the 4th, giving a speech approximately 90 minutes before the Navy aircraft reached their targets.

President Johnson asked for, and received, Congressional authority to use military force in Vietnam after the Gulf of Tonkin incident, which was described as a North Vietnamese attack on U.S. warships. Congress did not 'declare war', which is its responsibility in the Constitution of the U.S.A.; nevertheless, it launched what effectively was the longest war in U.S. history -- and even longer if the covert actions before the August 1964 Gulf of Tonkin situation are included.

The Gulf of Tonkin resolution, although later revoked, was considered, by Lyndon Johnson, as his basic authority to conduct military operations in Southeast Asia. It was another example of how declarations of war have become extremely rare since the Second World War.

Beginning of air operations
Immediately after the Gulf of Tonkin incident, there was a period of retaliation for specific attacks, Operation FLAMING DART, and then a steady but incremental pressure under Operation ROLLING THUNDER operations against North Vietnam. There was also extensive air support overtly inside South Vietnam, and, at different times, in Laos and Cambodia; some of these are discussed above in the section on covert activity.

From a current doctrinal standpoint, these campaigns should be evaluated according to thAn examination of air operations relies on a planning model at the level of operational art. This model distinguishes effectiveness, or the results of the campaign, from the tactical aspects of weapons effects. Several factors need to be considered to determine effectiveness. The campaigns in Laos and Cambodia were far more effective than Operation ROLLING THUNDER, as they were not executed as a subtle means of "signaling", but had clear objectives measurable in military terms. The objetives here, as well as in Operation LINEBACKER I, were military. Operation LINEBACKER II also was effective, but it had well-defined objectives at the level of grand strategy: compellence to return to negotiations.
 * 1) What conditions are required to achieve the objectives? (Ends)
 * 2) What sequence of actions is most likely to create those conditions? (Ways) (desired effects)
 * 3) What resources are required to accomplish that sequence of actions? (Means)
 * 4) What is the likely cost or risk in performing that sequence of actions?

Major ground combat phase
Secretary of Defense Robert McNamara, who had been appointed by Kennedy, became Johnson's principal adviser, and continued to push an economic and signaling grand strategy. Johnson and McNamara, although it would be hard to find two men of more different personality, formed a quick bond. McNamara appeared more impressed by economics and Schelling's compellence theory than by Johnson's liberalism or Senate-style deal-making, but they agreed in broad policy.

They directed a plan for South Vietnam that they believed would end the war quickly. Note that the initiative was coming from Washington; the unstable South Vietnamese government was not part of defining their national destiny. The plan selected was from GEN William Westmoreland, the field commander in Vietnam.

This model regarded the enemy forces in the field as the opposing center of gravity, as opposed to the local security and development of pacification. The enemy, however, had a different idea of centers of gravity; see Vietnamese Communist grand strategy.

Over time, the U.S. developed tactics increasingly appropriate to the environment and foe, given the Westmoreland's assumption that the center of gravity was the enemy main force. Some of the early operations included:

There were many such operations, variously by U.S. only, U.S. and ARVN, and ARVN forces. The term "search and destroy" was often used to describe ground operations against Viet Cong and People's Army of Viet Nam troops.

The UH-1 "Huey", as well as other types of helicopters, are iconic of the Vietnam War. The full capabilities of units with integrated helicopter support were shown by the 1st Cavalry Division (Airmobile) at the Battle of the Ia Drang and the Battle of Bong Son.

These operations continued, some joint with ARVN troops and some by U.S. and third country forces alone. Australian units, integrated into large U.S. forces, were highly regarded. Less mobile but potent divisions came from South Korea and Thailand.

Immense fire support, from ground and air platforms, supported these operations. Close air support both from fighter-bombers and early armed helicopters was common, but new techniques came into wide use. ARC LIGHT was the general code name for operations using B-52 heavy bombers against targets in South Vietnam. The term grew to encompass B-52 operations against targets in Cambodia and Laos, principally against the Ho Chi Minh trail. B-52 use in the major Operation LINEBACKER I and Operation LINEBACKER II operations against North Vietnam are generally not considered ARC LIGHT missions; see the respective operations.

There were also technical measures to clear jungle, both mechanical and chemical. See Vietnam War military technology.

Unquestionably, Westmoreland's approach inflicted immense casualties on the enemy forces. Even so, the North Vietnamese seemed willing to accept them. During the second half of 1967, the North Vietnamese intensified operations in the border regions of South Vietnam, in at least regimental strength. Unlike the usual hit-and-run tactics used by communist forces, these were sustained and bloody affairs. Beginning at Con Thien and Song Bein October 1967, then at Dak To

There had long been fighting in the Khe Sanh area, but the North Vietnamese greatly intensified their attacks in early January 1968, before the Tet Offensive. They continued operations there until April.

Tet offensive
By 1968, and perhaps in 1967, Johnson's chief adviser on the war, McNamara, had increasingly less faith in the Johnson-Westmoreland model. McNamara quotes GEN William DuPuy, Westmoreland's chief planner, as recognizing that as long as the enemy could fight from the sanctuaries of Cambodia, Laos, and North Vietnam, it was impossible to bring adequate destruction on the enemy, and the model was inherently flawed.

Opposition against him peaked in 1968; see Tet Offensive. On March 31, 1968, Johnson said on national television, "'I shall not seek, and I will not accept, the nomination of my party for another term as your president'"

In March, Johnson had also announced a bombing halt, in the interests of starting talks. The first discussions were limited to starting broader talks, as a quid-pro-quo for a bombing halt.:

Vietnamization phase
During the Presidential campaign, a random wire service story headlined that Nixon had a "secret plan for ending the war, but, in reality, Nixon was only considering alternatives at this point. He remembered how Eisenhower had deliberately leaked, to the Communist side in the Korean War, that he might be considering using nuclear weapons to break the deadlock. Nixon adapted this into what he termed the "Madman Strategy".

He told H.R. Haldeman, one of his closest aides, "I call it the madman theory, Bob.I want the North Vietnamese to believe that I've reached the point that I might do anything to stop the war. We'll just slip the word to them that for God's sake, you know Nixon is obsessed about communism. We can't restrain him when he's angry, and he has his hand on the nuclear button, and Ho Chi Minh himself will be in Paris in two days begging for peace."

After the election of Richard M. Nixon, a review of U.S. policy in Vietnam was the first item on the national security agenda. Henry Kissinger, the Assistant to the President for National Security Affairs, asked all relevant agencies to respond with their assessment, which they did on March 14, 1969.

U.S. policy changed to one of turning ground combat over to South Vietnam, a process called Vietnamization, a term coined in Janaury 1969. Nixon, in contrast, saw resolution not just in Indochina, in a wider scope. He sought Soviet support, saying that if the Soviet Union helped bring the war to an honorable conclusion, the U.S. would "do something dramatic" to improve U.S.-Soviet relations. In worldwide terms, Vietnamization replaced the earlier containment policy with detente. Also in 1969, both overt and covert Paris Peace Talks began.

While Nixon hesitated to authorize a military request to bomb Cambodian sanctuaries, which civilian analysts considered less important than Laos, he authorized, in March, bombing of Cambodia as a signal to the North Vietnamese. While direct attack against North Vietnam, as was later done in Operation LINEBACKER I, might be more effective, he authorized the Operation MENU bombing of Cambodia, starting on March 17. These bombings were kept secret from the U.S. leadership and electorate; the North Vietnamese clearly knew hey were being bombed. It first leaked to the press in May, and Nixon ordered warrantless surveillance of key staff.

Nixon also directed Cyrus Vance to to to Moscow in March, to encourage the Soviets to put pressure on the North Vietnamese to open negotiations with the U.S. The Soviets, however, either did not want to get in the middle, or had insufficient leverage on the North Vietnamese.

Final air support phase
In the transition to full "Vietnamization," U.S. and third country ground troops turned ground combat responsibility to the Army of the Republic of Vietnam. Air and naval combat, combat support, and combat service support from the U.S. continued. While the ARVN improved in local security and small operations, Operation Lam Son 719, in February 1971, the first large operation with only ARVN ground forces, they took casualties that the South Vietnamese leadership considered unacceptable, and withdrew. This operation still had U.S. helicopters lifting the crews, and U.S. intelligence and artillery support.

They did much better against the 1972 Eastertide invasion, but this still involved extensive U.S. air support. To stop the logistical support of the Eastertide invasion, Nixon launched Operation LINEBACKER I, with the operational goal of disabling the infrastructure of infiltration. One of the problems of the Republic of Vietnam's Air Force is that it never operated under central control, even for a specific maximum-effort air offensive. South Vietnamese aircraft always were controlled by regional corps commanders, so never developed skills in deep battlefield air interdiction.

When the North refused to return to negotiations in late 1972, Nixon, in mid-December, ordered bombing at an unprecedented level of intensity, Operation LINEBACKER II. This was at the strategic and grand strategic levels, attacking not so much the infiltration infrastructure, but North Vietnam's ability to import supplies, its internal transportation and logistics, command and control, and integrated air defense system. Within a month of the start of the operation, a peace agreement was signed.

Peace accords were finally signed on 27 January 1973, in Paris. U.S combat troops immediately began withdrawal, and prisoners of war were repatriated. U.S. supplies and limited advise could continue. In theory, North Vietnam would not reinforce its troops in the south. In practice, the North did not remove its large forces from the south, and eventually committed additional large forces in a conventional invasion.

Fall of South Vietnam
While Ford, Nixon's final vice-president, succeeded Nixon, most major policies had been set by the time he took office. He was under a firm Congressional and public mandate to withdraw

The North, badly damaged by the bombings of 1972, recovered quickly and remained committed to the destruction of its rival. There was little U.S. popular support for new combat involvement, and no Congressional authorizations to expend funds to do so. North Vietnam launched a new conventional invasion in 1975 and seized Saigon on April 30.

No American combat units were present until the final days, when Operation FREQUENT WIND was launched to evacuate Americans and 5600 senior Vietnamese government and military officials, and employees of the U.S. The 9th Marine Amphibious Brigade, under the tactical commmand of Alfred M. Gray, Jr., would enter Saigon to evacuate the last Americans from the American Embassy to ships of the Seventh Fleet. Ambassador Graham Martin was among the last civilians to leave. In parallel, Operation EAGLE PULL evacuated U.S. and friendly personnel from Phnom Penh, Cambodia, on April 12, 1975, under the protection of the 31st Marine Amphibious Unit, part of III MAF.

Vietnam was unified under Communist rule, as nearly a million refugees escaped by boat. Saigon was renamed Ho Chi Minh City.

Unquestionably, some American supporters were executed, and a much larger number imprisoned in "reeducation camps" for over a decade. Even larger numbers of South Vietnamese became refugees, many as desperate "boat people." Southeast Asia did not become a monolithic Communist bloc. It took over a decade for the U.S. military to recover from some of its internal turmoil and breakdown in discipline.