McNamara on why the United States became involved in Vietnam:
[The domino theory] was the primary factor motivating the actions of both the Kennedy and the Johnson administrations, without any qualification. It was put forward by President Eisenhower in 1954, very succinctly: If the West loses control of Vietnam, the security of the West will be in danger. "The dominoes will fall," in Eisenhower's words. In a meeting between President Kennedy and President Eisenhower, on January 19, 1961 -- the day before President Kennedy's inauguration -- the only foreign policy issue fully discussed dealt with Southeast Asia. And there's even today some question as to exactly what Eisenhower said, but it's very clear that a minimum he said ... that if necessary, to prevent the loss of Laos, and by implication Vietnam, Eisenhower would be prepared for the U.S. to act unilaterally -- to intervene militarily.

And I think that this was fully accepted by President Kennedy and by those of us associated with him. And it was fully accepted by President Johnson when he succeeded as President. The loss of Vietnam would trigger the loss of Southeast Asia, and conceivably even the loss of India, and would strengthen the Chinese and the Soviet position across the world, weakening the security of Western Europe and weakening the security of North America. This was the way we viewed it; I'm not arguing [we viewed it] correctly -- don't misunderstand me -- but that is the way we viewed it. ...

On JFK and Vietnam:
There were three groups of individuals among his advisers. One group believed that the situation [in South Vietnam] was moving so well that we could make a statement that we'd begin withdrawals and complete them by the end of 1965. Another group believed that the situation wasn't moving that well, but that our mission was solely training and logistics; we'd been there long enough to complete the training, if the South Vietnamese were capable of absorbing it, and if we hadn't proven successful, it's because we were incapable of accomplishing that mission and therefore we were justified in beginning withdrawal. The third group believed we hadn't reached the point where we were justified in withdrawing, and we shouldn't withdraw.

Kennedy listened to the debate, and finally sided with those who believed that either we had succeeded, or were succeeding, and therefore could begin our withdrawal; or alternatively we hadn't succeeded, but that ... we'd been there long enough to test our ability to succeed, and if we weren't succeeding we should begin the withdrawal because it was impossible to accomplish that mission. In any event, he made the decision [to begin withdrawing advisers] that day, and he did announce it. It was highly contested. ...

Kennedy hadn't said before he died whether, faced with the loss of Vietnam, he would [completely] withdraw; but I believe today that had he faced that choice, he would have withdrawn rather than substitute U.S. combat troops for Vietnamese forces to save South Vietnam. I think he would have concluded that U.S. combat troops could not save Vietnam if Vietnam troops couldn't save it. That was the statement he in effect made publicly before his death, but at that time he hadn't had to choose between losing Vietnam, on the one hand, or putting in U.S. combat troops on the other. Had he faced the decision, I think he would have accepted the loss of Vietnam and refused to put in U.S. combat troops.

On the 1963 coup in Saigon:
I believe the U.S. should not have given support to a coup. I think, in hindsight, most would agree with that conclusion. It was not a universal conclusion at the time, by any means.
I think one of the things it showed was that we didn't know either our opponents (in this case the North Vietnamese) or even our allies (in this case the South Vietnamese). I don't think we knew the society; I don't think we knew the leaders; I don't think we knew who was likely to follow [deposed South Vietnamese President] Diem. This was one reason that those who opposed the coup among Kennedy's advisers, one reason they opposed it. They couldn't get any indication of who was likely to follow, or whether the regime would be stable. And of course, what ultimately happened was, the regimes that followed Diem were not stable. It was like a revolving door: prime ministers were going in and out every few months or few weeks, over a period of time. But we as leaders, we as a society, did not properly understand, fully understand, as I suggest, either our allies or our opponents. ...

I'm only speculating now, but as I have learned more about the Vietnamese ... I've sensed the strong nationalism, the strong motivation that nationalism was to both the South and the North, and the strong nationalistic feelings of their leaders, Ho Chi Minh and Diem. Had Diem lived, I'm inclined to think he would neither have requested nor accepted the introduction of large numbers of U.S. combat forces. He would not have wished to put his nation in a sense under the control of a foreign power, even a friendly foreign power. I think the war would have taken a totally different course. Now that is only speculation, but I think it's an important point, because if I'm correct, it shows we didn't understand even our allies, much less our opponents. And this is one of the major lessons of the conflict.

On LBJ and Vietnam:
President Johnson, as Vice President under President Kennedy, had not been deeply involved in Vietnam. He'd visited Vietnam once or twice; he had been in many of the meetings, but he wasn't a major participant in them. But he in effect had inherited a war. He was determined to carry on Kennedy's policies, for a variety of reasons, and in a variety of areas: civil rights, but also in connection with Vietnam. Moreover, he had inherited Kennedy's advisers: the Secretary of State, Secretary of Defense, National Security Adviser, Chairman of Joint Chiefs, and so on. ...

We were deeply disturbed, deeply disturbed [by the unstable South Vietnamese government]. And the president, as a politician, was determined to do everything he possibly could to stabilize that government politically. He in effect sent me over there at one time, on one visit with Max Taylor, the Chairman of Joint Chiefs. He said, "I want to see you across that country on TV every day, supporting the President of Vietnam. We have got to stabilize that government." But there are limitations to what external military force can do. External military force cannot reconstruct a failed state, and Vietnam, during much of that period, was a failed state politically. We didn't recognise it as such. ... But he was determined to do everything within his power -- economic power, political power, military power -- to stabilize that nation politically. It proved impossible.

[LBJ] in a sense had to choose: was he prepared to give up South Vietnam and run the risk that Eisenhower pointed to, [that] the dominoes would fall? Or, if the South Vietnamese couldn't prevent that loss, was he prepared to put in U.S. combat troops, which violated Kennedy's belief that it was a Vietnamese war that only the South Vietnamese could win? And when he came to that point ... he said in effect: "I'm going to prevent the loss of South Vietnam; I'm going to prevent the dominoes from falling; I'm going to maintain the security of the West, and I'm going to put in U.S. troops to do it." Now, the decision wasn't as clear-cut at the time as I've made it sound today, but that was essentially the choice.

On the Gulf of Tonkin incident:
We were certain at the time that the first attack took place. I believe the date was August 2nd, 1964. We made every effort to be certain that we were right, one way or the other -- it had occurred or it hadn't occurred. And it was reported that there were North Vietnamese shell fragments on the deck of the U.S. destroyer Maddox. I actually sent a person out to pick up the shell fragments and bring them to my office, to be sure that the attack did occur. I am confident that it did; I was confident then, I am confident today. That was the August 2nd attack.

On August 4th, it was reported another attack occurred. It was not clear then that that attack had occurred. We made every possible effort to determine whether it had or not. I was in direct communication with the Commander-in-Chief of all of our forces in the Pacific (CINCPAC) by telephone several times during that day, to find out whether it had or hadn't occurred. He had reports from the commanders of the destroyers on the scene: they had what were known as sonar readings -- these are sound readings. There were eyewitness reports. And ultimately it was concluded that almost certainly the attack had occurred. But even at the time there was some recognition of a margin of error, so we thought it highly probable but not entirely certain. And because it was highly probable -- and because even if it hadn't occurred, there was strong feeling we should have responded to the first attack, which we were positive had occurred -- President Johnson decided to respond to the second [attack]. I think it is now clear [the second attack] did not occur. I asked [North Vietnamese] General Giap myself, when I visited Hanoi in November of 1995, whether it had occurred, and he said no. I accept that.

On the Gulf of Tonkin resolution:
Was Congress misled regarding the Tonkin Gulf resolution? Did they misunderstand the resolution? My answer, and it's important, is: yes and no. The resolution is very clear; the English language is clear in its expression in the resolution. The resolution gave full authority to the president to take the nation to war in Southeast Asia. Senator Cooper from Kentucky asked Senator Fulbright, who was the floor manager during the debate, "Does this resolution mean the President will have the authority to take the nation to war in Southeast Asia?" And Senator Fulbright said, "Yes." So there was no misunderstanding on that. But the Senate had been led to believe the president would not use that authority without seeking further counsel from the Senate; [and] he didn't [seek further counsel]. And in that sense, I think they were misled. ...

Both the hawks and the doves wished to avoid the debate [over committing U.S. forces]. At one point, President Johnson asked the leader of the hawks and the leader of the doves in the Senate: "Should we go back and ask the Senate to debate whether we should or shouldn't introduce U.S. forces, using the authority already granted to us by the Tonkin Gulf Resolution?" And both the hawks and the doves said, "No, don't bring it back - it'll tear us apart." And they were right in one sense. They were wrong on their conclusion that the resolution should not have been debated retroactively; [but] they were right it would have torn them apart. Why would it have torn them apart? Because the nation was divided at that time. Throughout the seven years I was in the Defense Department on Vietnam, the nation was divided. The majority of the people, the press and the Congress, throughout the seven years, up until early 1968, were in favor of preventing the fall of Vietnam, because they believed in the domino theory. And they were prepared to send U.S. troops and carry on U.S. combat operations in Vietnam to prevent that loss. But there was a growing minority, and had the issue actually been debated, it would have torn the Congress apart. And that was one of the reasons why the hawks and doves agreed it shouldn't be debated.

Beyond that, the President was fearful that if he raised this issue for public debate, there were many in the country and many in the Congress who believed that we should go all-out militarily to overcome North Vietnam -- including invading North Vietnam and bombing it to the point of genocide. And that was a very powerful force in the society, and the President was fearful that if he engaged in public debate, that that force would prevail. And he was determined -- and as a matter of fact, I was determined -- to avoid the risks that would follow from applying unlimited military force. In addition to a terrible loss of life that would have resulted from that, there was ... a risk of overt confrontation between the U.S. and China and the Soviet Union, overt military confrontation, including the possible use of nuclear weapons. On one or two occasions, the chiefs recommended U.S. military intervention in North Vietnam, and stated that they recognized this might lead to Chinese and/or Soviet military response, in which case, they said, "We might have to consider the use of nuclear weapons." The President was determined to avoid it; I was determined to avoid it. He was fearful that public debate would lead to greater pressure for that, and that's one of the reasons -- not the only reason, but one of the reasons -- he avoided public debate.

In any event, it was a very serious error on the part of the Johnson Administration. We did not fully debate the actions that led to the introduction of 500,000 troops, either with Congress or with the public. And that's one of the major lessons: no president should ever take this nation to war without full public debate in the Congress and/or in the public.

On the decision to introduce ground troops in Vietnam:
The events between January and July [1965] were such that the North Vietnamese were putting additional pressure on South Vietnam. South Vietnam was unable to respond effectively, and it became more and more clear that President Johnson was going to have to choose between losing South Vietnam or trying to save it by introducing U.S. military force and taking over a major part of the combat mission. He chose, rather than lose it, to introduce U.S. combat forces and take over the combat mission. And that was because he feared the dominoes would fall if he didn't do that. And I think the judgment was wrong -- I don't want to say his judgment [alone]: the judgment of all of us who were involved was wrong. But that was the fact at the time; that was what motivated him, it was what motivated us.
McGeorge Bundy and I sent [a memo] to the President, and we said in effect: "Mr President, we're following a course that cannot succeed. We cannot continue solely in providing training and logistical support. We've got to go beyond that, or we have to get out. And we're not certain which of these two alternatives should be pursued. Each should be debated. We're inclined to think we've got to get further in." Unfortunately, the two alternatives were not fully debated, and we slid into further intervention, which ultimately led to 500,000 troops over a period of two or three years.

On U.S. strategy in Vietnam:
The strategy was one of providing additional support to the South Vietnamese, to the point where it was believed they could prevail over the Viet Cong, which was being supported by North Vietnam at the time in the South; while at the same time, through the bombing of the North, applying sufficient pressure on the North to lead them to feel that they would pay a very heavy price if they continued to support the Viet Cong in the South. And the combination, it was believed ... would lead the North to change their policy. ...
Some of us questioned at the beginning whether [massive bombing] would ever achieve the objective. ... Some believed that the bombing ... would stop, in a sense, the ability of the North to resupply the South. Others believed bombing would not stop that. The record of my testimony before the Congress is clear on that; many of us believed it would be impossible, by bombing, to stop the flow of the small quantity of supplies needed in the South to support the Viet Cong. And I think the record shows the bombing didn't prevent that flow of supplies. Secondly, there were those who believed that the bombing would break the will of the North. Others believed it wouldn't. And it didn't.

On the war in general:
This was much more a civil war than a war of aggression. I'm not arguing that there wasn't an element of aggression in it; I'm not arguing that the Chinese and the Soviets might not have tried to use South Vietnam as a launching pad to knock over the dominoes of Malaysia and Thailand and Indonesia and whatever. But what I am arguing is that the conflict within South Vietnam itself had all of the characteristics of a civil war, and we didn't look upon it as largely a civil war, and we weren't measuring our progress, as one would have in what was largely a civil war. ...
It is said that the military operated with one hand tied behind their backs. To the extent that that refers to a restriction on land invasion by U.S. forces on North Vietnam, that's true. But today, General Westmoreland, who was the commander in Vietnam at the time, says that while at the time he felt he was constrained, he now understands that that was an effort by the president to prevent the U.S. coming into open military conflict with China and the Soviet Union. And Westmoreland says, "Thank God we avoided that. That was a correct policy at the time." Could more military pressure have been applied, in the sense of more bombing of the North? In one sense, no. We dropped two or three times as much bombs in North and South Vietnam as were dropped by all Allied Forces throughout World War II against all enemies. It was a tremendous air effort. But there are certain things bombing can't accomplish. They can't break the will of people under certain circumstances. They didn't break the will of the North Vietnamese. And it cannot stop the movement of the small quantities of supplies that were necessary to support the Viet Cong and the North Vietnamese forces in the South. They didn't, and it couldn't; and no additional amount of money [or] bombing could have. ...
As early as December 1965, I reported to the President that I believed there was no more than a one-in-three chance -- at best a one-in-two chance -- that we could achieve our political objectives, i.e. avoiding the loss of South Vietnam, by military means. And I strongly urged, therefore, [that] we increased our efforts on the political track, that we tried to move to negotiations with the North, to avoid the fall of the dominoes; and that, to stimulate a move toward negotiation, we stop the bombing. This was a very controversial move at the time. And we eventually did: we stopped for a month, in December 1965. It was one of about seven different attempts to move to negotiations, to stop the war to negotiate a solution that would yield a satisfactory outcome for the West, which was simply to avoid the loss of all Southeast Asia.
Those efforts were unsuccessful. I don't know why. I have proposed to Hanoi that ... we engage in examining what I think were missed opportunities for each of us, for them and us, to have avoided the war or to have terminated it earlier, with less loss of life, without any adverse effects on the geopolitical situations of either one of us. I very much hope those discussions will take place. We have much to learn from them that can be applied to the world of today and tomorrow. How to avoid these conflicts is something the human race has to learn. This century will go down as the bloodiest century in all of human history. We'll have lost 160 million people, killed by conflict. Is that what we want in the 21st century? I don't think so. If we want to avoid it, we have to learn from our mistakes in this century. Vietnam was one of those.