SNIE 100-7-58
22 JULY 1958
(Illegible)

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SPECIAL

NATIONAL INTELLIGENCE ESTIMATE

NUMBER 100-7-58

SINO-SOVIET AND FREE WORLD REACTIONS
TO US USE OF NUCLEAR WEAPONS
IN LIMITED WARS IN THE FAR EAST

Submitted by the
DIRECTOR OF CENTRAL INTELLIGENCE

The following intelligence organizations participated in the preparation of this estimate: The Central Intelligence Agency and the intelligence organizations of the Departments of State, the Army, the Navy, the Air Force, and The Joint Staff.

Concurred in by the
INTELLIGENCE ADVISORY COMMITTEE
on 22 July 1948. Concurring were The Director of Intelligence and Research, Department of State; the Assistant Chief of Staff, Intelligence, Department of the Army; the Director of Naval Intelligence; the Assistant Chief of Staff, Intelligence, USAF; the Deputy Director for Intelligence, the Joint Staff; and the Atomic Energy Commission Representative to the IAC. The Assistant Director, Federal Bureau of Investigation, abstained, the subject being outside of his jurisdiction.

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SINO-SOVIET AND FREE WORLD REACTIONS TO US USE OF
NUCLEAR WEAPONS IN LIMITED WARS IN THE FAR EAST

THE PROBLEM

This estimate was requested by the NSC as a result of a study prepared by the Departments of State and Defense and the Joint Chiefs of Staff, with appropriate participation of the Central Intelligence Agency, on US and Allied Capabilities for Limited Military Operations to 1 July 1961, 29 May 1958. Among the limitations under which this study was prepared were that it did not examine US and Allied capabilities against overtly employed Soviet armed forces; nor against an enemy employing nuclear weapons, since the latter case was construed as overt employment of Soviet forces. On the other hand, it was assumed that the US used nuclear weapons selectively from the outset in four hypothetical cases involving Communist aggression in the Far East.

This estimate examines whether or not the enemy would employ nuclear weapons if the US employed them, and assesses the impact on world attitudes if either the US or both sides employed them. It confines itself to assessing the above reactions in the four hypothetical cases given in the State-Defense study where the US employed nuclear weapons at the outset in response to Communist aggression through mid-1961: (1) North Korean invasion of South Korea, (2) Chinese Communist attack on Quemoy and Matsu, (3) Chinese Communist attack on Taiwan, and (4) North Vietnam attack on South Vietnam and Laos. It is based on the hypothetical situations which are developed in Appendices A-D of the State-Defense study and which are summarized at the outset of Sections III-VI of this estimate.

CONCLUSIONS

1. We believe that if the US used nuclear weapons in meeting Bloc local aggression in the Far East, there would be a grave risk that the Communists would retaliate in kind. Indeed any Far East Communist state, taking into account the possibility of such US action, would be unlikely to launch a local aggression without having received assurances of Soviet support.

2 We estimate that, though the USSR will be determined to avoid courses of action gravely risking general war throughout the period concerned, it probably calculates that its crowing military capabilities likewise increasingly deter the US from taking such risks. Therefore, fore, the Soviets would probably estimate that local Communist use of nuclear weapons in direct and localized response to their use by the US would not necessarily lead to expansion of hostilities into general war, and they would under certain circumstances be prepared to use such weapons.

3. If the Communists retaliated with nuclear weapons, they would attempt to do so in such a manner as to limit the risks of general war. The USSR itself would probably prefer to avoid open involvement, and would probably provide the necessary weapons to Communist China or North Korea, though retaining Soviet control. Moreover, the Communists would probably confine their use of nuclear weapons within limits comparable to those observed by the US.

4. The likelihood of Communist retaliation with nuclear weapons would be greatest if the US mounted nuclear attacks deep into Communist China, creating a situation to which Moscow and Pei-ping would almost certainly feel compelled to respond by attacks on US bases and nuclear capable forces in the Par East. If, in the case of Communist aggression against South Korea or Taiwan the US nuclear response were limited to Korea or the Straits area, the Communists would probably respond in kind in the same area. In the case of local aggression against Quemoy and Matsu or South Vietnam, the Communist response would be less certain. If US nuclear attacks were confined to the immediate Quemoy and Matsu areas or Vietnam and Laos, the Communists might attempt to win without using nuclear weapons or seek to break off the action. However, even if the US nuclear response were limited to the immediate area of Korea, Taiwan, Quemoy and Matsu, or Vietnam and Laos, we cannot exclude the possibility that the Communists would respond in kind, possibly including nuclear attacks against US bases in the area selected to minimize the additional risk of general war.

5. Many Free World governments and countries would be impressed and encouraged by the prompt US resistance to Communist aggression, but the US use of nuclear weapons would arouse widespread fear of general war and would tend to obscure Communist responsibility for initiating hostilities. The US would be widely condemned by popular opinion, especially in Asia, for the use of nuclear weapons. We believe that the adverse reactions would overshadow the favorable effects in most countries.

6. The adverse reaction would be mitigated if the US response quickly halted the fighting without causing large civilian casualties, and respect for US power would be enhanced. Even so, the stigma resulting from the US initiation of the use of nuclear weapons would not be removed. On the other hand, if the Communists responded with nuclear weapons and hostilities were prolonged and expanded, fears of general war would rise even higher, and great pressure would be exerted on the US to reach a settlement.1

[Footnote 1: The Deputy Director for Intelligence, the Joint Staff, agrees with the principal conclusions that:

a. US nuclear response to Communist aggression would be likely to result in Bloc response with nuclear attacks in the first two cases examined and less likely in the second two cases.

b. Considerable adverse political and psychological reaction, particularly in Asia, would initially result from US nuclear attacks.

The DDI, Joint Staff, disagrees, however, with certain lesser estimative judgments and estimative yardsticks applied in these conclusions and in the supporting discussion. He believes:

a. The paper fails to recognize adequately the meaning of selective US use of nuclear weapons; specifically, it tends to equate "selectivity" to geographical limitations on target areas. "Selectivity" also applies to weapons yield, precise target choice, and accuracy of delivery. Given these factors, references to "heavy civilian casualties" appear incompatible with the basic assumption.

b. The paper reaches certain qualitative judgments as to the relative weights of adverse popular reaction and favorable popular reaction to US nuclear attacks; these relative measurements are largely conjectural. Such judgments also appear to fail to give due weight to many factors which would influence popular reactions in addition to the fact that the United States employed nuclear weapons. Some of these additional factors would be the initial success achieved by US military forces, the public statements of US governmental leaders concerning US objectives and intentions, and the extent to which popular opinion clearly recognized the military action as resulting from Communist aggression. There would certainly be both applause and boos: to say that in most countries the boos would drown out the applause - as in the words ". . would overshadow. . ."— is to attempt a precision of estimating not considered feasible for the hypothetical situations being analyzed.]

DISCUSSION

I. THE GENERAL SINO-SOVIET MILITARY REACTION

A. Factors Bearing on the Initial Communist Decision to Attack

7. In our view the crucial determinant In any Sino-Soviet decision to initiate local aggression, or subsequently to respond In kind to US use of nuclear weapons in countering such aggression, would be the Sino-Soviet estimate of the resultant risks of general war. We continue to estimate that respect for US nuclear power will remain such that neither the Soviets nor the Chinese Communists are likely to pursue courses of action which in their judgment seriously risk general war. Largely for this reason, we do not believe that any of the four hypothetical cases of Communist aggression considered in this estimate is likely to occur through mid-1961.

8. We must assume, however, for the purposes of this estimate, that such aggression has taken place. Several consequences flow from this assumption. Most important, the Communists would have launched this aggression only after careful calculation of the likelihood of US intervention and of the resultant risks of general war. Both US statements and the general posture of the US forces in the Far East would almost certainly lead them to calculate that US intervention with nuclear weapons would be the only immediately effective US response.

9. The most likely calculations, therefore, under which the Communists would decide to launch local aggression in the Far East would be that the chances that the US would be deterred from even a local nuclear response were sufficient to justify taking the risk and that even If the US did respond, their own capabilities were sufficient both to cope with this reaction and to deter the US from broadening the conflict to general war. this circumstance might arise in the case of a substantial increase in Communist capabilities vis-à-vis those of the US, especially in the Far East — as tor example by the possible stationing of nuclear weapons and advanced delivery vehicles in Communist China. Particularly in this situation, the Bloc leaders might estimate that the US would be unwilling to accept the risks and the adverse Free World reactions involved in responding with nuclear weapons to Bloc attacks, and being unable to respond effectively in any other manner, would choose not to do so at all.

10. We believe it most likely that any Communist aggression in the Far East would be undertaken only in full consultation with Moscow, since the Chinese, North Koreans, or North Vietnamese would almost certainly insist upon certain guarantees of Soviet support in event of US retaliation beyond their capabilities to counter. However, we cannot exclude the possibility of unilateral action on the part of the Chinese Communists, based on their calculation that despite Soviet reluctance the USSR would be compelled to come to their support if the US replied with nuclear weapons. We regard such adventurism as unlikely, although possibly less so in the case of Quemoy and Matsu.

11. In any event, regardless of their estimate of the likelihood of US nuclear intervention, the Communists almost certainly would have made plans and preparations to meet this contingency. If the decision to launch a local war had been taken well in advance, Moscow might have already provided Peiping with some nuclear weapons and perhaps advanced means of delivery, both to deter a US nuclear response and to counter it if it came. We believe that in any event the Chinese will press the USSR for such weapons, and that the USSR may introduce these weapons into Communist China by 1961, although they will almost certainly remain under Soviet control. Alternatively, the Soviets might promise the Chinese to provide them quickly with such capabilities if required. Moscow would also probably attempt to deter the US at the time of the aggression by threats of intervention in case the US uses nuclear weapons.

B. Factors Bearing on the Subsequent Communist Reaction

12. Once Communist local aggression in the Far East had been launched, and the US had responded locally with nuclear weapons, Moscow and Peiping would face a critical decision. Broadly speaking, their reaction might range from abrupt termination of the conflict or seeking negotiations, through continuing the fight with conventional forces, to replying in kind with nuclear weapons.

13. As already staled, we believe the crucial determinant would be their estimate of the resultant risks of general war. Moscow and Peiping would be acutely conscious that the risks of general war had materially increased. The very fact of US use of nuclear weapons would reflect US determination to accept some risks. We believe, however, that if they had initially launched the aggression anticipating a US nuclear response and if they were confident of their capability to deal with it locally, They would promptly react with nuclear weapons themselves.

14. If, on the other hand, Moscow and Peiping had miscalculated our response, they might be more disposed to seek a quick settlement on the basis of the status quo ante rather than further increasing the risk of general war by a nuclear response of their own. Even In this case of initial miscalculation, however, the Soviets might regard their over-all nuclear deterrent power as making US resort to general war sufficiently unlikely that they could afford to take the risk of making a nuclear response. Moreover, they would have powerful additional reasons for a nuclear response, among them: (a) considerations of prestige, including a Soviet feeling that having threatened dire consequences if the US intervened with nuclear weapons, they must save face by following through; (b) the vulnerability of the US bases in the Far East; (c) on the Soviet side, the importance of supporting their chief ally; and (d) the damage to the Soviet deterrent posture if the USSR failed to respond.

15. The manner in which the US employed nuclear weapons could have a critical bearing on whether or not the Communists made a nuclear response. If such use were highly selective, and above all if confined to the immediate area of hostilities, the Communists might not respond with nuclear weapons But especially if the US launched nuclear strikes deep into Communist China, Peiping would almost certainly appeal desperately for Soviet assistance, and we believe that the Soviets would feel compelled to come to the support of their chief ally. They would probably calculate that they could not afford the loss to the Bloc and the blow to their own prestige and position of a crippling of Communist Chinese power.

16. The Communist reaction would also be conditioned by their appreciation of the general US posture at the time They would look to other US military movements, the degree of alert in the US. and US statements for evidence of whether the US was preparing to fight a prolonged local war if necessary, to expand the conflict, or to accept a return to the status quo. In this connection US statements of the limited nature of our objectives, if consistent with our military actions, might have considerable impact. Such statements might tend to reassure the Communists that a negotiated termination of the conflict on an acceptable basis was feasible. On the other hand, these statements might reassure them that their use of nuclear weapons locally would not lead the US to broaden the conflict.

17. If it appeared to the Communists that the US was not prepared to expand the conflict or to conduct a prolonged war, they would probably be more inclined to continue the fighting using nuclear weapons selectively. If on the other hand the US, while limiting Its initial nuclear response, nevertheless appeared determined to press on to victory, and prepared to expand the conflict in the Far East if necessary, the Communist reaction would tend to be more cautious. They might still launch some nuclear attacks to reduce US strike capabilities in an attempt to achieve a stalemate, but they would probably also move to secure an early end to the conflict.

C. The Modes of Sino-Soviet Nuclear Response

18. In case the Communists decided to react with nuclear weapons if the US had used such weapons in the Far East, Peiping and especially Moscow would nevertheless do so in such a manner as to limit the risks that hostilities would expand into general war. For this reason we believe that the Soviets would be loath to intervene directly through using identifiable Soviet forces to attack US bases and forces. They would probably prefer covertly to provide the necessary weapons and support to the Chinese Communists or possibly the North Koreans. We believe they would also calculate that the limited US base structure in the Far East would be highly vulnerable even to attack by Chinese Communist forces alone. But the Soviets would provide extensive aid and support, extending possibly to "volunteers." They would almost certainly provide Soviet forces to participate in the air defense of Communist China. Moreover, in event of widespread US attacks on Communist China, we cannot exclude the possibility of open Soviet intervention in the Far East.

19. Peiping and Moscow's desire to limit the risks of general war also would probably lead them to confine their nuclear attacks within limits comparable to those observed by the US. If US use of these weapons was confined to the immediate combat area, we believe that the Communists would similarly limit their response. However, the possibility cannot be excluded that even if US use of these weapons were confined to the immediate combat area, the Communists might also launch nuclear attacks against US bases in the Western Pacific selected so as to minimize the danger of general war. If the US attacked targets deep in Communist China, the enemy would probably react by attacking selected US bases in the Western Pacific.

II. GENERAL FREE WORLD REACTIONS

20. Free World reactions to a US response with nuclear weapons to Communist aggression in the Far East would vary widely. Provided that the aggression were clearly identifiable, most of our allies, and probably some neutral opinion, would be inclined, at least initially to view with approval our prompt and forthright aid to the victim of attack. However, this feeling would be overshadowed by fear that nuclear war in the Far East would spread into general war. Such apprehension would rise greatly if the US nuclear counterattack were of such a nature—including for example strikes deep into Communist China — that it appeared to be in excess of the force required, and particularly if the Communists employed nuclear weapons in retaliation. Even if the war were localized there would be fear that one side or the other might subsequently broaden it. These developments would lead to strong pressures on the part of other governments to seek a prompt end to hostilities.

21. Along with Free World fear of expanding hostilities would be a widespread adverse emotional reaction to US use of nuclear weapons Should these weapons inflict large casualties, particularly among civilians, it would intensify this feeling. If, however. US use of nuclear weapons led to a quick victory without large civilian casualties this altitude of repugnance would tend to diminish and to be offset by confidence in US deterrent power.

22. The adverse reaction to US use of nuclear weapons would be particularly strong throughout most of Asia. Here such use would lend to be looked upon as callous white indifference to the lives or Asians. Indeed the inflicting of large-scale casualties on Asian civilians might have enduringly adverse consequences for the anti-Communist position in Asia. The reaction in Japan would be especially adverse, in view of deep Japanese emotional antagonism to the use of nuclear weapons, and Japan would probably not allow US use of bases on its territory. The adverse reaction might be mitigated to a limited extent if the Communists in turn employed nuclear weapons, but the US would still incur the odium of having used them first.

III. THE CASE OF NORTH KOREAN INVASION OF SOUTH KOREA

23. Assumption. It is assumed for the purpose of this estimate that at a time when the situation in South Korea is confused following President Rhee's incapacitation, and rival groups are seeking power, the North Koreans charge South Korean border violations, step up subversive activities in South Korea, and then invade. Chinese Communist assistance to North Korea is covert, including troops disguised as North Koreans. It is also assumed that most US forces have been withdrawn prior to the attack. However, the US intervenes, initially largely with air power, and with subsequent commitment of ground forces as necessary. The US uses nuclear weapons against enemy military targets In Korea and China, the destruction of which is considered requisite to successful prosecution of the action. The US seeks UN backing, or, failing this, the support of the other fifteen members of the UN Command, but does not await such support before intervening.

A. The Sino-Soviet Military Reaction

24. The initial Communist attack on the ROK would probably only have been undertaken in anticipation that victory could be gained despite US counteraction, or that the US would be deterred from effective counteraction by the chaotic situation within the ROK, allied hesitancies, and fear of Sino-Soviet counter-moves. Nevertheless, the Sino-Soviet leaders, recognizing that the US might use nuclear weapons in Korea, would probably be prepared to counter this development by similar local use of nuclear weapons.

25. If the Initial US reaction were quick, effective, and limited to Korea, the Bloc might attempt to achieve a cease-fire, cut its losses, and redress its loss of face, in the belief that the fruits of victory were not worth the risks of expanded war. In this case it would attempt to exploit politically the US use of nuclear weapons, but we regard it as more likely that the Chinese Communists and North Koreans would reply with nuclear weapons obtained from the USSK.

26. If US use of nuclear weapons were restricted to North Korean targets, the Communists would probably use nuclear weapons only against targets in South Korea. However, we cannot exclude the possibility that if the attacks were launched from outside. Korea, the Communists might also launch nuclear attacks against US bases selected so as to minimize the additional risk of general war even though the US strikes had been confined to Korean territory. If a stalemate developed on the ground, a new armistice would be sought.

27. The likelihood of Communist nuclear reaction would be greatest in the event that US nuclear attacks were directed against targets in China itself. The Chinese Communists would probably attack with nuclear weapons selected US bases and naval forces in the West Pacific. If ballistic missiles capable of reaching these targets had been deployed in China prior to the aggression, they would also be used.

B. Free World Reactions

28. Assuming Bloc aggression appears clear-cut, the general attitude of the Free World, probably even including India and other neutrals, would initially be sympathetic toward the ROK and the United Stales. A large measure of diplomatic support would be forthcoming and some of our allies would be inclined to offer some token military assistance, though the US could not count on any significant Free World military support.

29. Free World sympathy would be overshadowed generally by (ear that the conflict would expand since the US had used nuclear weapons, particularly If the US attacked targets outside of Korea. Our principal NATO allies would probably seek to restrain the United States from continuing nuclear attacks. The neutralist countries would almost certainly have backed away from any initial approval. Conversely, if the Communists did not launch nuclear attacks, or if the conflict were effectively localized, concern over the spread of hostilities would diminish, and initial Free World approval of the US action would probably be strengthened. Even so, if heavy civilian casualties were inflicted, It would probably cause a feeling of revulsion, particularly in Asia, against the US.

30. From the outset, the Japanese reaction would constitute one of the greatest problems for the US. While the government and much of the public would be sympathetic to the US-ROK cause, fear of Japan's involvement would create great pressures to deny the United States the use of Japanese bases. US use of nuclear weapons, whatever the targets, would inflame Japanese reactions, public and official, almost certainly to the point of demanding that the US not use its bases in Japan for nuclear attacks. Japan might even insist on complete US withdrawal, particularly if the US expanded air attacks beyond Korea.

IV. THE CASE OF CHINESE COMMUNIST ATTACK ON QUEMOY AND MATSU

31. Assumptions. Two weeks of stepped-up artillery attack on the offshore islands, a buildup of jet fighters and bombers in the Southeast China area, and concentration of amphibious assault forces herald a coming invasion. GRC supply and reinforcement of the islands becomes difficult, due to heavy bombardment. In this charged atmosphere, Soviet spokesmen recall the 1950 Sino-Soviet Treaty of Mutual Assistance, and the US in turn stresses its Mutual Defense Treaty with the GRC. The US informs our allies that it will assist in repelling an invasion, using nuclear weapons, if necessary against mainland China. A general alert is declared throughout the Pacific Command. Japan announces it will never permit bases on its territory to be used for atomic warfare. When the invasion begins, the US immediately provides assistance to the GRC including selective nuclear attacks on military targets within a 500 n.m. radius from the islands (Including targets in the Shanghai, Nanking and Canton areas), and on enemy strike force bases wherever located in China, as well as on the invasion force itself.

A. The Sino-Soviet Military Reaction

32. Confronted with such an extensive nuclear response, Peiping and its Soviet aily would probably feel compelled to react with nuclear attacks at least on Taiwan and on the Seventh Fleet. Whether they would extend their attacks to other US Far East bases would depend largely upon whether these bases were used in our nuclear offensive and upon their assessment of our intentions. If US nuclear weapons were used extensively against interior Chinese targets, the Communists would probably feel compelled to respond against other US bases and forces in the Far East.

33. On the other hand, the firmness and promptness of our response would probably convince Peiping of our determination to retain control of Quemoy and Matsu. If at the same time our attacks were initially limited to forces and facilities in the immediate area and directly supporting the aggression, this factor might also convince Peiping that our objectives were limited to defense of the islands. Under these conditions, the Chinese Communists, if they had failed to seize the islands, would probably abandon the attempt despite the loss of face they would suffer from this defeat. This outcome would be most likely in the remote event that Peiping had launched the aggression without full Soviet concurrence and support. In this situation the USSR, despite Chinese Communist pressures, would probably seek to close out the actions as quickly as feasible, and attempt to compensate for Communist military defeat by political exploitation of the US use of nuclear weapons.

B. Free World Reactions

34. The predominant immediate Free World reaction to the US use of nuclear weapons against Communist China would be highly adverse, with many allies as well as the neutrals considering that the US was risking general war over what most of the world regards as unimportant parcels of real estate. Most of our allies, including those in NATO, would probably shun any responsibility for, or connection with, the US action, in an attempt to avoid involvement in hostilities developing from Quemoy and Matsu. In Asia, only a few countries, notably Nationalist China and South Korea, would be encouraged by the vigor of the US response to Chinese Communist aggression, whereas strong antagonism would be aroused generally throughout the continent by US use of nuclear weapons.

35. The adverse reaction would tend to be modified to the degree that the US action brought the hostilities to an early successful end without heavy civilian casualties. Under these conditions, even some Asian countries would probably come to have greater confidence In the ability of the United States to defend them against Communist aggression. But the reaction in most countries would remain adverse.

36. Conversely, if the conflict were prolonged or were to spread, and especially if large-scale casualties were inflicted on Chinese civilians, the adverse consequences for the US might be irreparable, particularly in Asia. We might be forced to withdraw from our bases in Japan, and Japanese pressure for our withdrawal from Okinawa would increase. Our influence in most other Asian countries would be seriously undermined. In Western Europe fears of general nuclear war and popular pressures on governments to end the fighting would increase.

V. THE CASE OF CHINESE COMMUNIST INVASION OF TAIWAN

37. Assumptions. As a result of effective Chinese Communist interdiction of the offshore islands, the GRC successfully evacuates Quemoy and Matsu, unopposed and with the assistance of the US Seventh Fleet. There follows a buildup of invasion forces and air-power in East China. The GRC calls on the UN to condemn such war preparations, and asks for military assistance; the US reiterates readiness to aid the GRC if It is attacked. Japan announces it will never consent to its bases being used for atomic warfare, while the Philippines and South Korea-announce their support of the GRC. There is a 7-10 day warning period before the actual attempted invasion, during which US forces could deploy in the area. Upon the actual invasion attempt, the US renders assistance by air and naval forces, employing nuclear weapons against the enemy invasion forces, enemy bases for the attack (including air bases wherever located), and any successful enemy lodgment on Taiwan. If this does not fully succeed, SAC is to be employed against other Chinese Communist forces and the warmaking capabilities of Communist China. All present US bases in the area are used, except those in Japan.

A. The Sino-Soviet Military Reactions

38. Since Chinese Communist invasion of Taiwan would require the commitment of a significant portion of the Chinese Communist armed forces, and would in Peiping's eyes carry great risk of US nuclear intervention, we regard it as almost certain that Peiping would not undertake such an operation without prior assurances of Soviet support. Furthermore, we believe that the Sino-Soviet leaders would have regarded the likelihood of US nuclear intervention to be sufficiently great that they would have deployed Soviet nuclear weapons (under Chinese Communist cover) in East China. In the assumed case, the Bloc would probably calculate either that the US would be deterred by fear of Bloc nuclear retaliation from responding with sufficient force to thwart the invasion, or that Bloc nuclear capabilities were sufficient to cope with US nuclear intervention.

39. If the initial US response with nuclear weapons were limited to the attacking forces and the immediate area of Taiwan, and particularly if it quickly defeated the Initial Chinese Communist attempt at invasion, the Communists might seek to close out the war quickly, preferring military defeat to expanded war. They might calculate that their loss of military prestige would in part be compensated by propaganda dividends from US use of nuclear weapons against Asians and that the ultimate effects in weakening the US position in Asia might be considerable.

40. However, the extent to which Chinese Communist prestige had been committed by an operation of this size and the difficulty of reaching a settlement which the Chinese Communists could accept without loss of face might lead the Bloc to retaliate with nuclear weapons even if this meant serious risk of expansion of hostilities in the Far East. Accordingly, if they decided to continue the campaign in the face of US nuclear attacks in the Taiwan Straits area, they would retaliate with similar nuclear attacks upon bases in Taiwan and upon the Seventh Fleet.

41. If the US extended the area of its nuclear attacks deep into mainland China, we believe that the chances of Communist nuclear counterblows would be substantially greater. The USSR would be faced with the difficult decision either of permitting its major ally to suffer a humiliating defeat, or of taking the risks involved in the necessary steps to prevent such a defeat. We estimate that the Communists would launch reciprocal nuclear strikes against selected US bases and naval forces. If ballistic missiles capable of reaching these targets had been deployed in China prior to the aggression, they would also be used.

B. Free World Reactions

42. Even though most Free World countries would recognize that Communist aggression had clearly occurred, this factor would be outweighed by concern throughout the Free World lest World War III result from the postulated US use of nuclear weapons. Most of our allies, including those in NATO, would probably think that protection of Taiwan was not of sufficient importance to warrant actions which they would consider to promote serious risk of general war, or even of major war in the Far East. Some of them would express some support of the US, but they would exert strong pressure for a ceasefire. Popular pressures on Allied governments for ending the fighting would increase, as would sentiment for restricting US ability to launch nuclear strikes from bases elsewhere in the world. The US would almost certainly be denied the use of its bases in Japan for the campaign.

43. The adverse reaction would tend to he modified to the degree that the US action brought the hostilities to an early successful end without heavy civilian casualties. Under these conditions, even some Asian countries would probably come to have greater confidence in the ability or the United States to defend them against Communist aggression. But the reaction in most countries would remain adverse

VI. THE CASE OF NORTH VIETNAMESE INVASION OF SOUTH VIETNAM AND LAOS

44. Assumptions. The Vietnamese Communists infiltrate the equivalent of two regular divisions and as many irregulars into all the Indochinese states, and concentrate a dozen divisions of regular forces in North Vietnam. Sporadic clashes occur and there is a spate of assassinations in Vietnam. President Diem proclaims a state of national emergency and siege, invokes the SEATO treaty, and calls for aid from all members. There is no clear cut beginning of the invasion. US military action would include the selective use of nuclear weapons as appropriate, against the invading forces, targets in North Vietnam, and in adjacent areas of Communist China The US, before moving, advises Communist China and the USSR of its intention to assist Vietnam militarily unless the invaders withdraw.

A. The Sino-Soviet Military Reaction

45. In Initiating the attack on South Vietnam, the Bloc would almost certainly have counted on achieving its objectives before an effective US Intervention could develop, and possibly on deterring any US intervention at all. Once the US nuclear response occurred, the Bloc would be confronted with a difficult choice among; (a) seeking a negotiated settlement; (b) continuing the war without Bloc use of nuclear weapons, calculating that the US would not in this case employ nuclear weapons against Communist China itself; or (c) reacting by use of nuclear weapons against US forces, with the resultant risks involved.

46. If US use of nuclear weapons were restricted to targets in Indochina, there is an even chance that the Communists would attempt to continue the campaign without using nuclear weapons themselves. In this case, the Bloc would continue to provide military assistance and equipment to the North Vietnamese, including a buildup of Communist air power. If the Communists were able to continue effective military operations in South Vietnam and Laos despite US use of nuclear weapons the impact in Asia would be substantial. If US-Vietnamese forces were threatening to cross the 17th Parallel they would probably seek to close out the conflict on the basis of restoration of the status quo. Should North Vietnam nevertheless be invaded, Chinese Communist forces would probably enter in force to hold at least the Hanoi-Haiphong and northerly areas. In this case, the Communists would also probably threaten to use — and indeed might use — nuclear weapons in Indochina itself to stave off defeat.

47. Moreover, if at any stage the US made nuclear attacks on adjacent areas in China, the Communists would probably respond with nuclear attacks on targets in Indochina, and possibly on selected US bases in other countries.

B. Free World Reactions

48. Initial support among Free World governments and peoples for US determination to resist Communist aggression would be offset in large measure if the US used nuclear weapons. Opposition to US use of nuclear weapons would be particularly strong if the US attacked targets In Communist China, even if Communist Chinese use of "volunteers" in Vietnam were large-scale and widely known. As in the previous cases, opposition to US use of nuclear weapons would be sharpest in Asia. 49. If the US response Involved only limited and selective use of nuclear weapons in Indochina alone, the reaction of most US Allies would be less adverse. Such action would have the support of South Korea and Nationalist China, and would have the support of some SEATO governments if they thought this action necessary to repel the aggression. However, the reaction of most Free World countries, and particularly of the Asian neutrals, would still be generally adverse, even if the conflict remained localized and the aggression were turned back.