208. National Intelligence Estimate1

NIE 4–68

THE CLANDESTINE INTRODUCTION OF WEAPONS OF MASS

DESTRUCTION INTO THE US

The Problem

To assess the capabilities of foreign nations to introduce biological, chemical, or nuclear weapons clandestinely into the US, and to estimate the likelihood of such introduction over the next few years.

Conclusions

A.
Virtually any industrial nation could produce biological warfare (BW) and chemical warfare (CW) agents and introduce them clandestinely into the US in relatively small quantities. We do not believe, however, that any potential enemy would plan the clandestine use of BW or CW on a scale sufficient to achieve strategic military objectives. We do not rule out the use of BW or CW for sabotage and other special purposes for which they could be very effective. The relatively small quantities required for these purposes could be covertly produced in the US without great difficulty or risk of detection. Therefore we consider that their clandestine introduction would be unnecessary, and unlikely in view of the risks involved.
B.
The Soviets could introduce nuclear weapons clandestinely into the US, and might consider doing so if they planned a deliberate surprise attack on the US. Considering the large numbers of strategic weapons now in their arsenal, however, the Soviets would see the contribution of a clandestine emplacement effort as marginal and would consider any advantages it offered as outweighed by the risks of jeopardizing surprise and of precipitating a US preemptive attack.
C.
Because the Chinese have no other means of attacking the US with nuclear weapons, they might consider a clandestine emplacement effort with the object of deterring the US from attack on Communist China. Their capabilities to carry out such an effort, however, are much less than those of the USSR. Moreover, they could not be sure that the US would be deterred and they would have to consider that detection might result in, rather than stave off, a devastating US strike. For these reasons, we think it unlikely that Communist China will attempt to introduce nuclear weapons clandestinely into the US.
D.
We have considered the possibility that a third country (e.g., Cuba) might assist the USSR or China in the clandestine introduction of nuclear weapons into the US. We consider this unlikely. We doubt that either the Soviets or the Chinese would seek to enlist the aid of another nation in such a sensitive undertaking. If they should, that nation’s leaders would almost certainly react unfavorably to a proposal that could jeopardize their national survival merely to support Soviet or Chinese policy.

Discussion

I. Introduction

1.
In considering the clandestine introduction of weapons of mass destruction into the US, enemy leaders would have to weigh any possible advantages against the grave consequences which would follow from discovery. Despite all precautions there would always be risk of detection arising not only from specific US security measures, but also from the chance of US penetration of the clandestine apparatus, the defection of an agent, or sheer accident. The enemy leaders would almost certainly judge that use of this tactic would be regarded by the US as a warlike act, if not as a cause for war, and that it would precipitate an international political crisis of the first magnitude.
2.
We believe, therefore, that the range of circumstances in which weapons of mass destruction might be clandestinely introduced into the US is quite narrow—that an enemy nation would consider this course only in the context of planning an attack on the US or of deterring the US from an attack on itself. Smaller stakes would not be worth the risk. Such weapons could not be brought in secretly in sufficient [Page 704]quantities to have a decisive effect on the outcome of a war. Any plans for their use, we believe, would envision the use of limited quantities to achieve results unattainable by other means.
3.
Virtually any industrial nation could produce biological warfare (BW) and chemical warfare (CW) agents and introduce them clandestinely into the US in relatively small quantities. Although small quantities of BW agents could be effective against large targets, the delayed action of such agents makes them unsuitable for use in situations requiring an immediate or precisely timed effect. Relatively large quantities of CW agents are required to obtain effective concentrations over extensive target areas, and it would be difficult to introduce them clandestinely in such quantities. Moreover, the effects of BW and CW agents cannot always be predicted accurately; adverse weather can limit or even prevent the effective use of BW and CW agents against some targets.
4.
We do not rule out the use of BW and CW for sabotage and other special purposes for which they could be very effective. But because the relatively small quantities required for these purposes could be covertly produced in the US without great difficulty or risk of detection, we consider that their clandestine introduction would be unnecessary, and therefore unlikely in view of the risks involved. The following discussion, therefore, is limited to a consideration of the clandestine introduction of nuclear weapons.
5.
Only four foreign nations—the USSR, the UK, France, and Communist China—have developed and tested nuclear weapons. Beyond these, only India is likely to undertake a nuclear weapons program in the next several years; Israel and Sweden might do so. We can foresee no changes in the world situation so radical as to motivate the UK, France, or any of the potential nuclear powers to attempt to clandestinely introduce nuclear weapons into the US. For this reason, the balance of this discussion will be concerned only with the remaining nuclear powers, the Soviet Union and Communist China.

II. Soviet and Chinese Capabilities

6.
Both the USSR and Communist China can produce nuclear weapons which could be adapted for clandestine introduction into the US. [11 lines of source text not declassified]
7.
Nuclear weapons with weights of up to 1,500–2,000 pounds could be brought across US borders by common means of transport without great difficulty. [1–1/2 lines of source text not declassified] a Chinese weapon could yield [less than 1 line of source text not declassified]. The difficulties and risks of introducing higher yield or heavier weapons into the US, even in a disassembled state, are probably sufficiently [Page 705]great to seriously discourage such attempts. But higher yield weapons could be brought into US waters in merchant ships and detonated without removal from the ship. Such devices could also be carried in by fishing boats or similar small craft to which transfer had been made at sea.
8.
Both the USSR and Communist China could make the physical arrangements necessary to bring nuclear weapons secretly into the US, but Soviet capabilities in this respect are much greater than Chinese. We believe that if either country undertook such a program, they would rely on their own agent organizations rather than on political sympathizers in the US. Soviet intelligence services have assigned a high priority to the development of espionage and sabotage capabilities in the US and presumably have formed an organization for the latter purpose. Should the Soviets undertake the clandestine introduction of nuclear weapons, they almost certainly would employ the highly trained and reliable agents of these services. They could also employ diplomatic personnel and could bring in weapons or weapon components under diplomatic cover. The large diplomatic establishments in Canada and Mexico could serve as bases for the operation.
9.
There are no Chinese Communist diplomatic establishments in the US, Canada, or Mexico. The absence of such bases precludes the use of diplomatic pouches for the clandestine introduction of nuclear weapons or their components and the use of secure diplomatic communications for planning and control of such an operation; it also makes more difficult the introduction and control of agents. Nevertheless, the Chinese could introduce agents under the guise of bona fide immigrants.
10.
In considering Soviet and Chinese capabilities, we have also considered the possibility that a third country (e.g., Cuba) might assist the USSR or China in the clandestine introduction of nuclear weapons into the US. We consider this unlikely on two counts. We doubt that either the Soviets or the Chinese would seek to enlist the aid of another nation in such a sensitive undertaking. And if they should, that nation’s leaders would almost certainly react unfavorably to a proposal that could jeopardize their national survival merely to support Soviet or Chinese policy.

III. Strategic Considerations

11.
If the Soviets or Communist Chinese have considered the clandestine introduction of nuclear weapons into the US, they have almost certainly been influenced by the same general considerations: the element of risk, the opportunities for clandestine introduction, and the results that could be achieved. The two countries, however, occupy [Page 706]vastly different strategic positions vis-à-vis the US. Thus, while we believe that neither would consider the use of this tactic except in the context of a possible general war, differing strategic considerations might lead the Soviets and the Chinese to see the clandestine introduction of nuclear weapons in a somewhat different light.
12.
The USSR . The Soviet leaders, like those of the US, must take account of the possibility of general war in their military planning. In such planning, the Soviets would consider the clandestine introduction of nuclear weapons into the US, if at all, only as a supplement to the main attack by their large strategic attack forces. Because they have already achieved an assured retaliatory capability, they would probably consider a clandestine emplacement effort as potentially useful only in support of a deliberate or preemptive Soviet attack and directed toward delaying or reducing a US retaliatory attack. Possible targets might include important government headquarters, key military command and control facilities, missile detection and tracking radars, and possibly some manned alert forces. The Soviets would recognize, however, that even if such an effort were successful, it could not prevent US retaliation or reduce it to an acceptable level.
13.
In considering clandestine attack as a supplement to other weapons, the Soviets would have to weigh their ability to initiate such attack rapidly, with little preparation, and in close coordination with the main weight of attack. Thus, clandestinely introduced weapons would have to be in position at the time the attacks were launched. In the case of a preemptive attack, the circumstances would not allow sufficient time for the introduction and delivery of such weapons after a decision to preempt. To prepare for this contingency beforehand, the Soviets would have to accept the risk of maintaining weapons in the US for an indefinite period of time. These difficulties would not obtain if the USSR decided deliberately to initiate general war in a period of low tension; weapons could be introduced into the US a relatively short time before use. But the Soviets would have to consider the risk of jeopardizing the element of surprise on which this course of action relies, and that discovery might precipitate a US preemptive attack which would be disastrous for the USSR. For these reasons, we think it unlikely that the USSR will attempt to introduce nuclear weapons clandestinely into the US.
14.
Communist China. The Chinese have no capability at present to attack the US with nuclear weapons. They probably have an ICBM system in the early stages of development, which could become operational several years from now. But they may fear that when it does the US antiballistic missile deployment will have rendered it largely ineffective. In these circumstances, they might see some advantages in clandestinely introducing and emplacing nuclear weapons in the US. [Page 707]Inasmuch as they could not deliver such an attack on a scale sufficient to achieve a decisive military objective, their object would presumably be to deter the US from a course of action that gravely threatened their national security. Consequently, the most likely targets would be population centers.
15.
Clearly, the Chinese would also see grave disadvantages in such a move. So long as the US was unaware of their existence, the concealed weapons would have no effect upon its actions. Indeed, the risk of their discovery would be an ever-present, continuing danger to the Chinese themselves. Once the Chinese announced that nuclear weapons were emplaced in the US, the announcement would touch off an intensive search and extraordinary security measures. Moreover, the Chinese could not be sure that the US would in fact be deterred. On the one hand, the US might consider such an unverified announcement as a mere bluff. On the other it might take the clandestine introduction of such weapons as a casus belli and, having taken such action as it could to safeguard its population, launch a devastating nuclear attack on China. [3 lines of source text not declassified] It is conceivable that some Chinese regime might be willing to accept such risks of national destruction, but we think it unlikely.
  1. Source: Johnson Library, National Security File, Intelligence File, Miscellaneous CIA Memoranda [4 of 4], Box 14. Top Secret; Restricted Data. A title page and prefatory note are not printed. According to the prefatory note, the CIA and the intelligence organizations of the Departments of State and Defense, the Atomic Energy Commission, and the National Security Agency participated in the preparation of this estimate. Representatives of the CIA, Department of State, DIA, NSA, and AEC concurred; the FBI representative abstained, the subject being outside his jurisdiction.