Central Intelligence Agency, Board of National Estimates, "Use of Nuclear Weapons in the Vietnam War," 18 March 1966, Secret

C01133628 APPROVED FOR RELEASE DATE: JAN 2005 (b) (3) TOP SECRET TS# 185929-e CENTRAL INTELLIGENCE AGENCY OFFICE OF NATIONAL ESTIMATES Cy. 13 10 March 1966 MEMORANDUM FOR THE DIRECTOR SUBJECT: Use of Nuclear Weapons in the Vietnam War CONCLUSIONS A. Use of nuclear weapons by the US in the Vietnam war would be one of the most important events of modern history. World reactions would be affected to some extent by the circumstances in which the US resorted to their use, and the targets attacked. But almost independent of these factors would be a widespread and fundamental revulsion that the US had broken the 20-year taboo on the use of nuclear weapons. B. Among the consequences would be intense agitation in Japan, probably leading to a restriction on US use of Japanese facilities and possibly to denunciation of the US-Japan defense treaty; probably some accelerated momentum toward nuclear proliferation; accompanied, however, by international pressure for disarmament in the nuclear field, with scant patience for the technicalities of verification; a probable resolution of condemnation in the UN; and a marked diminution of such public support as US policy in Vietnam now has. TOP SECRET GROUP 1 Excluded from automatic downgrading and declassification

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C. It is possible that once the US had used nuclear weapons the Chinese Communists might move to disengage, but we think it more likely that they would not do so, but would hope that accumulating US losses and mounting world pressures would force the US to back down. The DRV would have been reduced to a secondary role. The USSR would act vigorously against the US on the political and propaganda front; we do not believe that it would enter the war or support the Chinese with nuclear weapons.

DISCUSSION

I. SCENARIO

1. It will be argued in this paper that foreign reactions to US use of nuclear weapons in the Vietnam war would be determined far more by the fact that the weapons were nuclear than by the circumstances in which they were used or the provocations which might have led the US to use them. Nevertheless, the circumstances would make some difference, at least in certain quarters. The following short list of conceivable scenarios begins with one in which US use of nuclear weapons would appear least justifiable in the eyes of the world generally and least in accord with Communist expectations, and proceeds to the one which is at the other extreme in these respects.

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(a) The military situation in South Vietnam remains essentially as at present; the US employs nuclear weapons out of sheer frustration at its inability to obtain any decision by conventional means.

(b) The US invades North Vietnam, either overland or by amphibious assault, or both; the Chinese Communists intervene in large combat force, either overtly or with "volunteers," and the US forces in North Vietnam find themselves threatened with destruction.

(c) The US does not invade North Vietnam. But the PAVN, plus Chinese Communist ground forces, launch the largest scale overt invasion of South Vietnam of which they are capable, across and around the demilitarized zone. They may also come into northern Laos in strong force. US and South Vietnamese forces may or may not be seriously endangered; in any event a new phase of the war is opened by Chinese and DRV initiative.

(d) The area of conflict is expanded by Chinese Communist initiative, involving invasions of Laos, Thailand, and perhaps Burma.

(e) The Chinese Communists themselves first use a nuclear weapon.

2. Neither the first nor the last of these scenarios appears worth serious consideration; they are both so highly unlikely as to be virtually out of the question, and they are included only to illustrate the possibility of situations different from those which we shall discuss. Within each of the three middle scenarios there are, no doubt, a large number of possible attendant circumstances which would have some bearing on the situation and might modify to

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some small degree the judgments which the world made of the US nuclear response, and alter the reactions to it. Because the effect of such variations would almost certainly be minor it does not seem useful to attempt to explore any of them in detail. The discussion which follows applies principally to situation (c) -- a large-scale Communist invasion of South Vietnam -- but we have included some references to the differences in reaction which might be expected in situations (b) or (d).

II. REACTIONS IN THE NON-COMMUNIST WORLD

3. In the non-Communist world there are a good many people who neither know nor care much about nuclear weapons and would not react one way or the other if the US used them in Vietnam, particularly so long as the danger seemed remote from themselves. There are governments which, whatever their public pronouncements on the subject, would in the light of their particular national interests be glad to see the Chinese Communist regime destroyed by this means. There are also individuals and governments who would consider the United States weak if it allowed substantial numbers of its armed forces to be destroyed without attempting to save them by the use of nuclear weapons. And there are some who would consider the United States foolish to accept defeat or even compromise in the Vietnam struggle without having recourse to its most formidable element of military power.

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4. Granting these and perhaps some other exceptions, there is in the field of international affairs probably no more universal opinion than that which holds the use of nuclear weapons to be abhorrent. Any use of nuclear weapons by the US in the Vietnam war would be viewed as among the most fearful and fateful events of modern history. World reactions would be affected to some extent by the conditions under which the US resorted to their use and the kinds of weapons and targets involved. But almost independent of these factors would be a fundamental revulsion that the US had broken the 20-year taboo on the use of nuclear weapons.

5. The use of atomic bombs against Japan in 1945 is still condemned by many, not only abroad but within the US. Most informed opinion, however, recognizes that it was intended to hasten the end of a long and bloody world war. Most important, it is seen as a bad moment of history that occurred nearly a generation ago and must never be repeated.

6. Over the years, world opinion has been generally surprised and relieved to discover that the US-Soviet nuclear race, rather than precipitating a war between the two powers, has tended to make

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such a war "unthinkable." Nuclear bombs and warheads thus tend to be looked upon as weapons which will never be used except in a world bent on self-destruction. It has come to be felt that the chances of a nuclear holocaust have significantly receded in recent years because the two super-powers are led by responsible governments which are prepared to go to great lengths to see that nuclear weapons will never again be employed.

7. Their use in Vietnam, regardless of the circumstances, would send a wave of fear and anger through most of the informed world. The general feeling would be that, once the taboo had been broken, there would remain no effective barrier to expanded use of such weapons. People would fear that the Communists would respond in kind if they had, or could acquire, a nuclear capability. Behind all this would lie a fear that the use of nuclear weapons might lead to a general nuclear war endangering the world at large.

8. Most friends of the US would condemn it for having dragged the world into a new and terrible phase of history in which nuclear weapons had become the working weapons of the times. Resolutions of condemnation would be introduced in the UN with the likelihood of winning a majority vote. NATO would be badly shaken. Such public support as US policy in Vietnam now receives from a number of governments, especially in Europe, would be ended.

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9. A British government which failed to make a public condemnation of the introduction of nuclear weapons into the Vietnam fighting would probably fall. In Japan, memories of Hiroshima and Nagasaki would make the people especially resentful of a second use of US nuclear weapons against Asians. At a minimum, Prime Minister Sato would feel compelled to end his support of US policy, and, in particular, to restrict the US use of Japanese facilities. More likely, the Liberal-Democratic Party would replace Sato with someone less identifiably pro-US in his views. It is possible that, under leftist prodding, the popular reaction would force a move to close US bases or even to denounce the US-Japan defense treaty. Most opinion in India and the Indian government would strongly condemn the US action, though some Indian leaders would be relieved to see the Chinese Communists set back, and some would be secretly pleased if Chinese nuclear facilities were destroyed. The general Indian condemnation would be somewhat reduced if the nuclear weapons were used to stop a Chinese invasion of Southeast Asia.

10. A very limited use of tactical weapons in only the immediate battle area would cause a less violent reaction in sophisticated circles than would the nuclear bombing of Chinese

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airfields, rail centers, and nuclear production sites. But to much of the world the distinction would not be significant; the important thing would be that these weapons had been used at all. The circumstances under which the weapons were used would also have some effect on reactions. The most severe reaction would occur if the US had invaded North Vietnam (case 'b'); on the other hand, the negative reactions would be reduced if nuclear weapons were employed as a last resort to stop the Communist Chinese from overwhelming the whole of Southeast Asia. Indeed, in this case some positive support would be manifested.

11. Beyond these direct reactions, there would be other effects having a growing impact in the future. There would probably be a wave of international pressure for immediate disarmament in the nuclear field. Most of this would be aimed at the US as the only nation to have used such weapons, and there would be little patience with continued US insistence on the need for inspection. It is possible, however, that some of this pressure could be diverted to the Soviets in the form of demands for "real" and "verified" disarmament.

12. Yet, paradoxically, there would probably also be an accelerated momentum toward nuclear proliferation. A US use which

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"legitimatized" nuclear weapons and demonstrated their critical importance and practicability in today's wars would lead some governments to feel they must have such weapons in their arsenals. At the same time, the US argument against proliferation would lose moral credit and encounter cynical reactions.

III. REACTIONS OF THE KEY COMMUNIST COUNTRIES

13. Communist China. The Chinese Communist leaders are quite conscious of the potent nuclear arsenal of the US. In adopting a policy involving the probability of war with the US, they would have considered the possibility that nuclear weapons might be used. They might have concluded that international and domestic pressures would prevent the US from using nuclear weapons under any conditions short of a direct threat to its national survival. They could not be certain of this, however, and their plans would have included courses to follow if nuclear weapons were used.

14. It is possible that once the US used nuclear weapons, the Chinese might move to disengage, particularly if they had not expected the US to do so. We think it more likely, however, that once committed, the Chinese would attempt to continue in spite of nuclear weapons. In the belief that they could eventually prevail,

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they would probably press on, accepting the military consequences while trying to minimize them by dispersal, close-embrace battlefield tactics, and an intensification of guerrilla warfare behind the US lines. They would hope thus to prolong the struggle to the point where accumulating US losses and mounting world pressures would force the US to back down.

15. The USSR. Moscow would be alarmed at the prospect of continued escalation which might force it into a nuclear confrontation with the US. It would take steps on all fronts to reduce the likelihood of such a development. It would act vigorously on the propaganda and political front, striving to generate sufficient international pressure in and out of the UN to force the US to pull back from its escalation. The Soviets would probably feel compelled to warn the US that the USSR would support China with military aid. At the same time, however, they would make it clear to Peking not to count on Soviet nuclear weapons. They would almost certainly not provide any nuclear weapons to the Chinese.

16. The DRV. With the war having expanded to the point where the Chinese were directly involved and nuclear weapons had been introduced, the DRV would have been reduced to a secondary role. The PAVN/VC would retain a significant capability in the

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South, but in the big picture they would have become an adjunct of the Chinese forces. In the event that the use of nuclear weapons so alarmed the DRV as to lead it to wish to quit the war, the Chinese involvement and presence would probably have foreclosed this option. They could end the war only if Peking concurred.

IV. LONGER TERM IMPLICATIONS

17. If the tactical use of nuclear weapons succeeded in turning back the Chinese and helped lead to a quick and advantageous settlement in Vietnam, there would be many gains for the US to set against the losses mentioned above. "Nothing succeeds like success," and many would forgive the US once the danger receded. Asian allies of the US would feel much more secure against Chinese encroachments. Peking, badly set back, would lose prestige, and this might lead to a reappraisal of the leadership by the masses and the younger party leaders. The Soviets would gain new fear and respect for the US hard liners; their conviction of the danger of "wars of national liberation" would be confirmed. At the same time, those in the USSR who advocate greater stress on military development and are unenthusiastic about detente would have their hands strengthened.

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18. If the US used nuclear weapons with some persistence and still failed to turn back the Chinese or bring a quick end to the war, the results would be serious indeed. The comparative impotence of the US and of its most vaunted weapons in coping with a "revolutionary struggle" would have been demonstrated to Peking's satisfaction and advantage. At the same time, the US would pay the whole political cost of having used these weapons in the first place.

19. There remains, of course, the question of the consequences of not using nuclear weapons, and of accepting a military disaster, perhaps extending to loss of the war, which these weapons might have averted. Such a development would have profound implications for the standing of the US in the world and for the balance of power in Asia. Examination of these implications, however, would involve consideration of the whole subject of US objectives and policies in Southeast Asia, and does not come within the scope of this paper.

FOR THE BOARD OF NATIONAL ESTIMATES:

ABBOT SMITH Acting Chairman

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