The effects of the South Vietnamese government's poor performance from Ngo Dinh Diem's death until the middle of 1965 have been understood widely, but its causes have not. According to one standard explanation, the Saigon government failed because its leaders and its American advisers selected the wrong methods for combating the enemy. In truth, however, the problem was not in the concepts but in the execution. An explanation more commonly advanced, closer to the mark but still only partially correct, is that the South Vietnamese government faltered at this time because the country's ruling elite was bereft of strong leaders. Many individuals who occupied positions of power in the post-Diem period, it is true, did lack the necessary leadership attributes, and none was as talented as Diem, but the caliber of the elites as a whole was not a critical problem. The critical problems, rather, were the exclusion of certain elites from the government and the manipulation of governmental leaders by the militant Buddhist movement. From November 1963 onward, the top leadership in Saigon repeatedly removed men of considerable talent, either because of their past loyalty to Diem or because of pressure from the militant Buddhists. And in spite of these purges, the government still had some men, even at the very top at times, who possessed leadership capabilities that would have made them successful leaders had it not been for militant Buddhist conniving. The Buddhist leaders tried to bridle every government that held power after Diem, and in most instances they succeeded, largely because government officials feared resisting the Buddhist activists after watching Diem lose American favor, and his life, for resisting them. As its American advocates had desired, the 1963 coup led to political liberalization, but rather than improving the government as those Americans had predicted, liberalization had the opposite effect, enabling enemies of the government to undermine its prestige and authority, as well as to foment discord and violence between religious groups. Not until June 1965, by which time the United States and most South Vietnamese leaders had come to realize the necessity of suppressing the militant Buddhists and other troublemakers, would political stability return. By then, however, South Vietnam had sustained crippling damage and Hanoi was pushing for total victory.

Lyndon Johnson's lack of forcefulness in Vietnam in late 1964 and early 1965 squandered America's deterrent power and led to a decision in Hanoi to invade South Vietnam with large North Vietnamese Army units. According to the prevailing historical interpretation, the leadership in Hanoi relentlessly pursued a strategy of attacking in the South until it won, with little regard for what its enemies did. In reality, however, North Vietnam's strategy was heavily dependent on American actions. Although Johnson's generals favored striking North Vietnam quickly and powerfully, he chose to follow the prescriptions of his civilian advisers, who advocated an academic approach that used small doses of force to convey America's resolve without provoking the enemy. Because of his chosen strategic philosophy and because of international and U.S. electoral politics, Johnson made only a token attack on North Vietnam following the Tonkin Gulf incidents of 1964 and undertook no military action thereafter. Rather than inducing the North Vietnamese to reciprocate with self-limitations, as the theorists predicted, however, this approach served only to heighten Hanoi's appetite and courage. Johnson's lack of action, as well as his presidential campaign rhetoric, convinced Hanoi that the Americans would not put up a fight for Vietnam in the near future. This change came at a time when the weakened condition of the Saigon government indicated that South Vietnamese resistance to a North Vietnamese invasion would be weak. Consequently, in November 1964, Hanoi began sending large North Vietnamese Army units to South Vietnam, with the intention of winning the war swiftly. The Americans were slow to identify the shift in North Vietnam's strategy and thus lost any remaining chance of deterring Hanoi or otherwise enabling South Vietnam to survive without U.S. combat troops.

Some well-known historians have argued that President Johnson wanted to inject U.S. ground troops into the war whether they were needed or not. Johnson made his decision to intervene, they contend, at the end of 1964 or in early 1965. In actuality, Johnson reached his decision no earlier than the latter part of June 1965, by which time intervention had become the only means of saving South Vietnam. The first U.S. ground troops sent to Vietnam arrived in March 1965, but Johnson deployed them only to protect U.S. air bases, not to engage the main elements of the Communist forces. At the time of the initial ground force deployments, Johnson and his lieutenants did not foresee a major war between American and Communist forces, because they did not know that Hanoi had begun sending entire North Vietnamese Army regiments into South Vietnam. They did not learn of this development until the beginning of April. By the middle of June, abetted by a continuing infusion of North Vietnamese soldiers, the Communist forces had won many large victories and the South Vietnamese Army was losing its ability to challenge large Communist initiatives. The North Vietnamese had entered the third and final stage of Maoist revolutionary warfare, in which the revolutionaries use massed conventional forces to destroy the government's conventional forces. Hanoi's ultimate success, as its leaders repeatedly stated, depended above all on the ability of its conventional forces to destroy the South Vietnamese Army, particularly its mobile strategic reserve units, not South Vietnam's small counter-guerrilla forces. The fighting of 1965 demonstrated that, contrary to the contentions of a multitude of pundits and theoreticians, the Americans and the South Vietnamese had been correct to develop a large conventional South Vietnamese army during the 1950s and early 1960s rather than concentrate exclusively on small-unit warfare.

Lyndon Johnson had always wanted to avoid putting U.S. troops into the ground war if there was any way that South Vietnam could continue the war without them. Like most of his advisers, he doubted that U.S. ground force intervention would result in an easy victory, believing instead that it would result in a long, painful, and politically troublesome struggle against an enemy who might never give up. But in June 1965, Johnson and his military advisers concluded, correctly, that only the use of U.S. ground forces in major combat could stop the Communist conventional forces from finishing off the South Vietnamese Army and government. Even as Johnson became convinced of the need for intervention, he held out hopes of withdrawing U.S. troops from Vietnam relatively soon, regardless of how the fighting was going, in the belief that a brief intervention might achieve as much as a sustained intervention in terms of preserving U.S. credibility and prestige in the world.

Johnson decided that South Vietnam was worth rescuing in 1965 primarily because he dreaded the international consequences of that country's demise. His greatest fear was the so-called domino effect, whereby the fall of Vietnam would cause other countries in Asia to fall to Communism. Historians have frequently argued that Johnson fought for Vietnam primarily to protect himself against accusations from the American Right that he was soft on Communism, which would have harmed his reputation and denied him the political support he needed to carry out his domestic agenda. In actuality, the domestic political ramifications of losing Vietnam had relatively little influence on Johnson's decision on whether to protect South Vietnam. Johnson recognized that the American people were largely apathetic about Vietnam and would be no more likely to turn against him politically and personally if he left than if he stayed and fought. Domestic political considerations did, on the other hand, exert great influence on how Johnson protected South Vietnam, as they discouraged him from bridling Ambassador Henry Cabot Lodge, from taking a tough stance on Vietnam before the 1964 election, and from calling up the U.S. reserves and otherwise putting the United States on a war footing. That there has been great cynicism and confusion about Johnson's motives was partly the responsibility of the President himself, for during this period he repeatedly misrepresented his intentions to the American people and he did not provide decisive leadership that would have clarified his views and inspired the people's confidence.

The domino theory was valid. The fear of falling dominoes in Asia was based not on simple-mindedness or paranoia, but rather on a sound understanding of the toppler countries and the domino countries. As Lyndon Johnson pondered whether to send U.S. troops into battle, the evidence overwhelmingly supported the conclusion that South Vietnam's defeat would lead to either a Communist takeover or the switching of allegiance to China in most of the region's countries. Information available since that time has reinforced this conclusion. Vietnam itself was not intrinsically vital to U.S. interests, but it was vital nevertheless because its fate strongly influenced events in other Asian countries that were intrinsically vital, most notably Indonesia and Japan. In 1965, China and North Vietnam were aggressively and resolutely trying to topple the dominoes, and the dominoes were very vulnerable to toppling. Throughout Asia, among those who paid attention to international affairs, the domino theory enjoyed a wide following. If the United States pulled out of Vietnam, Asia's leaders generally believed, the Americans would lose their credibility in Asia and most of Asia would have to bow before China or face destruction, with enormous global repercussions. Every country in Southeast Asia and the surrounding area, aside from the few that were already on China's side, advocated U.S. intervention in Vietnam, and most of them offered to assist the South Vietnamese war effort. The oft-maligned analogy to the Munich agreement of 1938 actually offered a sound prediction of how the dominoes would likely fall: Communist gains in one area would encourage the Communists to seek further conquests in other places, and after each Communist victory the aggressors would enjoy greater assets and the defenders fewer.

Further evidence of the domino theory's validity can be found by examining the impact of America's Vietnam policy on other developments in the world between 1965 and the fall of South Vietnam in 1975, developments that would remove the danger of a tumbling of Asian dominoes. Among these were the widening of the Sino-Soviet split, the Chinese Cultural Revolution, and the civil war in Cambodia. America's willingness to hold firm in Vietnam did much to foster anti-Communism among the generals of Indonesia, which was the domino of greatest strategic importance in Southeast Asia. Had the Americans abandoned Vietnam in 1965, these generals most likely would not have seized power from the pro-Communist Sukarno and annihilated the Indonesian Communist Party later that year, as they ultimately did. Communism's ultimate failure to knock over the dominoes in Asia was not an inevitable outcome, independent of events in Vietnam, but was instead the result of obstacles that the United States threw in Communism's path by intervening in Vietnam.

It has been said that the Johnson administration, in its first years, could have negotiated a U.S. withdrawal from Vietnam that would have preserved a non-Communist South Vietnam for years to come. Evidence from the Communist side, however, reveals North Vietnam's complete unwillingness to negotiate such a deal. The Communists would not have agreed to a settlement in 1964 or 1965 that could have prevented them from gaining control of South Vietnam quickly. With their list of military victories growing longer and longer, with a clear and promising plan for conquering South Vietnam on the battlefield, the North Vietnamese had no reason to accept a diplomatic settlement that might rob them of the spoils.

The Americans did miss some strategic opportunities of a different sort, opportunities that would have allowed them to fight from a much more favorable strategic position. In the chaotic period following Diem's overthrow, the Joint Chiefs of Staff and other U.S. military leaders repeatedly advocated an invasion of North Vietnam. Johnson and his civilian advisers rejected this advice, however, on the grounds that an American invasion of the North could lead to a war between the United States and China. Historians have generally concurred in the assessment that Chinese intervention was likely. But the evidence shows that until at least March 1965, the deployment of U.S. ground forces into North Vietnam would not have prompted the Chinese to intercede. Having suffered huge losses in the Korean War, the Chinese had no more appetite for a war between themselves and the Americans than did their American counterparts. Johnson's failure to attack North Vietnam also worked to the enemy's advantage by facilitating a massive Chinese troop deployment into North Vietnam, which in turn freed up many North Vietnamese Army divisions for deployment to South Vietnam and made a subsequent U.S. invasion of North Vietnam much riskier.

Another opportunity not taken -- one that never carried a serious risk of war with China -- was the cutting of the Ho Chi Minh Trail with American forces. Johnson rejected many recommendations from the Joint Chiefs to put U.S. ground forces into Laos to carry out this task, and on this point, too, historians have backed the President over his generals. The Johnson administration and some historians have argued that the Ho Chi Minh Trail was not essential to the Communist war effort, but new evidence on the trail and on specific battles makes clear the inaccuracy of this contention. The Viet Cong insurgency was always heavily dependent on North Vietnamese infiltration of men and equipment into South Vietnam through Laos, and it could not have brought the Saigon government close to collapse in 1965, or defeated it in 1975, without heavy infiltration of both. Other orthodox historians have argued that an American ground troop presence in Laos would not have stopped most of the infiltration, but much new evidence contradicts this contention as well. The United States, moreover, missed some valuable opportunities to sever Hanoi's maritime supply lines, although it did cut some of the most important sea routes in early 1965.

In sum, South Vietnam was a vital interest of the United States during the period from 1954 to 1965. The aggressive expansionism of North Vietnam and China threatened South Vietnam's existence, and by 1965 only strong American action could keep South Vietnam out of Communist hands. America's policy of defending South Vietnam was therefore sound. U.S. intervention in Vietnam was not an act of strategic buffoonery, nor was it a sinister, warmongering plot that should forever stand as a terrible blemish on America's soul. Neither was it an act of hubris in which the United States pursued objectives far beyond its means. Where the United States erred seriously was in formulating its strategies for protecting South Vietnam. The most terrible mistake was the inciting of the November 1963 coup, for Ngo Dinh Diem's overthrow forfeited the tremendous gains of the preceding nine years and plunged the country into an extended period of instability and weakness. The Johnson administration was handed the thorny tasks of handling the post-coup mess and defending South Vietnam against an increasingly ambitious enemy -- and in neither case did the administration achieve good results. President Johnson had available several aggressive policy options that could have enabled South Vietnam to continue the war either without the help of any American ground forces at all or with the employment of U.S. ground forces in advantageous positions outside South Vietnam. But Johnson ruled out these options and therefore, during the summer of 1965, he would have to fight a defensive war within South Vietnam's borders in order to avoid the dreadful international consequences of abandoning the country.

Triumph Forsaken by Mark Moyar Published by Cambridge University Press; August 2006;$32.00US; 0-521-86911-0