One of the great problems in arms control is that advances in technology, and their application to military programs, tend to invalidate or render meaningless even the soundest arms-control proposals. Twice in the last decade this has occurred, once when the diffusion of nuclear technology and the production of large numbers of nuclear weapons rendered futile any hope of complete nuclear disarmament, and again when the advent of intercontinental missiles made necessary a rethinking of all the proposals for limiting or abolishing strategic strike forces. It may well be that we are about to witness a similar overtaking of current arms-control proposals because of the possibility of deploying highly effective ballistic missile defenses.

Although work on anti-ballistic missiles has been under way for some years, the prospects for their being really effective have in the past seemed relatively small. As Secretary of Defense McNamara and others have indicated, this was due largely to the development of sophisticated penetration aids (chaff, decoys, nose cones whose wakes were not easily identifiable by radar, etc.), so that incoming warheads could not be readily distinguished at the optimum altitudes for engagement by anti- ballistic missiles. Under these circumstances, the cost/effectiveness of such missiles was relatively low, in that an enemy could penetrate missile defenses with comparative ease. Alternatively, he could simply bypass local defenses by striking at undefended targets or by exploding large-yield weapons up-wind from defended ones. To cope with this latter threat, and with the possibility of fallout-or even blast damage-from defending missiles detonated at low altitudes, ballistic missile defenses had to be complemented by shelters capable of protecting against fallout and resistant to blast pressure. All in all, it is understandable that the United States did not deploy anti-ballistic missiles during the early sixties.

However, in the past year or so, a number of developments have called that decision into question. The first of these was the discovery that long- range interceptors could destroy incoming warheads beyond the atmosphere, before they dropped to altitudes at which current types of penetration aids would be effective in confusing the missile defense radars. Moreover, the extended range of these interceptors meant that fewer anti-missile missiles could protect a larger area, thereby reducing both the number of batteries which would have to be deployed and the cost of a defensive system. Even when combined with terminal defenses around targets of particular importance, new types of ballistic missile defenses appear to be more flexible and less costly than those which were under consideration a year or two ago.

A second relevant development was the detonation by the Chinese of a series of nuclear devices, several of which, according to the U.S. Atomic Energy Commission, "included thermonuclear material," and one of which was mated with a short-range missile. Even though a Chinese intercontinental ballistic missile force may, as Mr. McNamara testified, be seven or eight years off, the prospect of such a force gives rise to understandable concern. A system of anti-ballistic missiles which intercepted targets beyond the earth's atmosphere ("exo-atmosphere") could certainly reduce damage from attacks by small nuclear powers such as China, as well as degrade second strikes or uncoördinated attacks by larger powers and guard against accidental launchings.

The third development has been an apparent step-up of Soviet activity in anti-ballistic missiles. Although the U.S.S.R. has for some years been working on anti-missile missiles, and has even televised films of missile interceptions, evidence of the actual installation of missile defenses has been both scant and contradictory; thus, while President Johnson, in his State of the Union Message, referred only to the emplacement near Moscow of "a limited anti-missile defense," other sources have spoken of Soviet A.B.M. sites athwart the natural access routes of incoming U.S. missiles, and have described the Soviet program as a nationwide net. Even limited Soviet ballistic missile defenses could, as General Maxwell D. Taylor stated some years ago, have a significant political and psychological impact, while more extensive ones might to some degree erode American strategic superiority.

Anyone concerned with the security of the United States must, therefore, pay close attention to the potentialities of ballistic missile defenses for limiting damage from a nuclear strike, or, in a larger sense, for helping to deter such a strike. However, it is not enough to consider the case in so narrow a context, since national security embraces concerns other than that of damage limitation and may prescribe means of achieving that security other than large and costly expenditures for defensive systems. Thus, those deciding whether, how and when to deploy ballistic missile defenses must consider their broad effects, taking into account possible Soviet reactions, the impact on friends and allies of such a decision, and the political and sociological implications of such a move for the United States. They must also consider other means of advancing our interests and security, the impact on the arms race, the implications for agreement on further arms-control measures, the possible effect on past agreements such as the nuclear test-ban treaty, and the options open to the United States if it deems these factors important.

II

As previously indicated, technological improvements in ballistic missile defenses make feasible the deployment of a system which could markedly reduce the damage from an attack of a given magnitude. This has led to suggestions for at least the partial or "light" deployment of anti- ballistic missiles as a defense against lesser nuclear powers-and specifically against Communist China. It is argued not only that anti- missile missiles could reduce damage from a Chinese Communist attack, but also that they would render such an attack less likely, thereby enhancing the credibility of the American deterrent and giving the United States greater freedom of action in containing or opposing Chinese Communist expansionism in South and Southeast Asia. It is also maintained that the deployment of ballistic missile defenses may advantageously influence Chinese plans for weapons procurement, and specifically that it may induce the Chinese not to build intercontinental ballistic missiles. A look at both these possibilities is in order.

Broadly speaking, the Chinese Communists have two choices: to attempt to develop a regional deterrent based on light or medium bombers, medium-range or intermediate-range ballistic missiles and submarine-launched missiles; or to aim at a global deterrent, composed of long-range bombers, intercontinental ballistic missiles and more advanced submarine-launched missiles. Whether they will, in the long run, follow one or both of these routes is less important than the fact that the current constraints on their resources almost force them into a minimal program; indeed, Secretary McNamara's postulated Chinese I.C.B.M. threat is almost a decade off.

Considering these constraints, the possible uses of Chinese nuclear power, and the political advantages of deploying a visible deterrent as soon as possible, it may well be that the Chinese will forgo for the time being the deployment of intercontinental ballistic missiles-whether or not the United States installs anti-ballistic missiles. However, this would not preclude the Chinese from developing a capability to launch small-scale attacks against the United States, which they could do either with conventional delivery vehicles such as small ship-borne or submarine-carried seaplanes, or with more exotic vehicles such as submarines equipped to fire nuclear- tipped torpedoes against port installations and coastal cities. In fact, it is possible that the Chinese may find it advantageous to build submarine- launched missiles rather than intercontinental ballistic missiles. In the first place, they now have submarines, they have fired short-range missiles, and they would find it fairly simple to adapt these, or to build rather crude forms of sea-based missiles. In the second place, a missile submarine force would give them both a regional and an intercontinental capability, at least to the extent of small-scale attacks upon coastal cities. Furthermore, such a force would be less vulnerable to preëmptive attack than either bombers or the kinds of first-generation "soft" I.R.B.M.s and I.C.B.M.s that are likely to be within Chinese capabilities.

Moreover, while fear of Chinese retaliation against the United States may inhibit our freedom of action vis-à-vis Communist China, there are other inhibiting factors, ranging from the possibility of Soviet intervention to concern over the political and psychological consequences of drastic measures-factors which certainly operated prior to the time the Chinese developed nuclear weapons. To these must be added the deterrent effect of a regional Chinese capability, which could enable the Chinese to strike at American bases in East Asia or even to threaten the cities of our Asian allies. While such a regional deterrent may not in itself have the impact of an intercontinental one-especially since it may not suffice to "trigger" a Soviet strategic strike against the United States-it will certainly strengthen the present barriers to U.S. military intervention in Asia.

Entirely aside from the question of whether ballistic missile defenses are necessary to deter Chinese nuclear strikes against the United States, it is also questionable whether they will have the desired impact on the Chinese development of particular weapons systems; they may simply induce the Chinese to emphasize weapons programs with which ballistic missile defenses (and particularly exo-atmospheric defenses) cannot readily cope, weapons such as submarine-launched cruise-type missiles. In any case, as China's technology and industrial capacity grows, so also will the sophistication of its weapons. To counter this, we will probably find it necessary to extend, to deepen and perhaps to improve our anti-ballistic missile system and to build up our air defenses and antisubmarine warfare forces. Thus, whatever the initial form of an A.B.M. system designed for use against Communist China, it will ultimately become either largely ineffective or little different from that required to defend against Soviet forces. In the long run, therefore, ballistic missile defenses capable of coping with a Chinese attack are likely to increase markedly our capability to limit damage by Soviet strategic forces-a point which the U.S.S.R. is not likely to miss.

This raises immediately the question whether ballistic missile defenses are really needed against the Chinese Communists, who do not now possess, nor are likely to possess in the next decade, a strategic strike force sufficient to constitute a serious threat to the United States. For the Chinese to attack, or to threaten to attack, American cities in the face of our strategic superiority would be the rashest of acts on the part of a people who have been noted for their caution and conservatism in the use of military power.[i] Indeed, it is rather astonishing that the United States, which seems satisfied that its deterrent is effective against the Soviet Union, should be so concerned about its ineffectiveness against a power whose resources are miniscule, whose opportunities for significant gains through limited war are considerably less than those of the Soviet Union, and which, moreover, has shown no signs of undertaking such adventures.

III

Whatever the American decision with respect to deploying anti-ballistic missiles against Communist China, it is obvious that this may not be controlling; even should the United States refrain from building ballistic missile defenses, the U.S.S.R. might do so. In view of the tests they have conducted, the boasts they have made of the capabilities of their anti- missile missiles, and their thinking concerning the role of defenses as a stabilizing influence, it is entirely possible that the Soviets may extend to other areas the missile defenses now surrounding Moscow-if indeed they have not already done so. In this case, much will depend upon how we react.

One option, of course, would be to do nothing, on the grounds that the strength, the diversity and the sophistication of our strategic strike forces now in being or currently programmed would enable them to overcome Soviet defenses, should the necessity ever arise. Although this may suffice militarily, especially against small-scale missile defenses around a few Soviet cities, it has severe drawbacks in other respects; as an unidentified official of the Johnson Administration is reported to have said, the President "could be crucified politically . . . for sitting on his hands while the Russians provide a defense for their people."[ii] And if the Soviets extended their ballistic missile defenses to the extent that they significantly eroded American strategic delivery capabilities, the pressures to respond with some sort of arms buildup would be almost irresistible.

This could take the form of strengthening strategic strike forces, with the primary aim of insuring, as President Johnson said in his State of the Union Message, "that no nation can ever find it rational to launch a nuclear attack or to use its nuclear power as a credible threat against us or our allies." A second aim might be to retain the ability to limit damage through counter-force attacks against Soviet missile sites, air bases and other strategic targets. In seeking to achieve these aims, the United States would have, broadly speaking, four choices: to penetrate, to overwhelm, to bypass or to evade Soviet ballistic missile defenses. While any of these options could probably maintain our capacity for "assured destruction," they would obviously have quite different implications for damage-limitation, for possible Soviet reactions and, consequently, for the size and the cost of American strategic strike forces.

It is significant that Mr. McNamara, in response to the apparent acceleration of the Soviet A.B.M. program, has chosen to upgrade American strategic strike forces rather than to expand them. Both the Minuteman III, which replaces an earlier version, and the Poseidon submarine-launched missile, which is a successor to Polaris, can carry numerous penetration aids and/or multiple warheads, which, in Mr. McNamara's judgment, would "increase greatly the overall effectiveness of our Assured Destruction force . . . even if the Moscow-type A.B.M. defense were deployed at other cities as well. . . ." Although the introduction of multiple warheads theoretically increases the number of targets at which the United States could strike, these warheads may seem less threatening to the U.S.S.R. than would comparable increases in the size of our missile forces. And in this instance, as in many others, appearance may be as important as reality.

Had Mr. McNamara's proposal been, instead, to saturate segments of the Soviet defenses through timed salvos of missiles, or to exhaust them through the sheer number of missiles launched, this would probably require not only multiple warheads but also larger missile forces. The same would be true if the objective were to bypass their defenses by striking at more lightly defended targets or launching missiles along paths which would avoid the heaviest concentrations of defensive installations. The consequent expansion of American missile forces, which are already three times as big as those of the U.S.S.R., could appear to enhance the U.S. counterforce capability and thus threaten the Soviets' own capacity for deterrence. Their logical response would be to expand their Strategic Rocket Forces, and perhaps to place greater reliance on mobile missiles, thus touching off a further round of increases by the United States, and so on.

Interestingly enough, Mr. McNamara has apparently ruled out the option of evading Soviet ballistic missile defenses, which would have meant relying more heavily on weapons systems, such as bombers and cruise-type missiles, that could not be degraded by Soviet A.B.M.s; in fact, he indicated that "a new highly survivable I.C.B.M. would have a far higher priority than a new manned bomber." Since bombers have little or no intrinsic first-strike counterforce capability, they might pose less of a threat to the Soviet deterrent than would an expansion of missile forces, and might provoke other-or milder-Soviet reactions. For the same reason, however, they might make less of a contribution to damage-limitation than would more or better missiles. In sum, the decision to penetrate any future Soviet A.B.M. system, rather than to overwhelm, evade or bypass it, seems to reflect careful consideration of possible Soviet reactions, as well as of our defense needs.

There is, of course, an alternative to strengthening offensive forces, and that is to build defensive ones-a step recommended by the Joint Chiefs of Staff and endorsed by some influential members of Congress. Here also there are a number of options, ranging from the installation of anti-missile missiles around I.C.B.M. sites to the full-scale deployment of both area and local ballistic missile defenses designed to protect American cities.

As Mr. McNamara testified, the first option is only one possible way of preserving our "assured destruction" capability in the face of unexpected increases in the size and the effectiveness of Soviet missile and missile- defense forces, and must be compared with other ways of preserving that capability; moreover, it would not reduce damage from a Soviet attack on American cities. A "light" A.B.M. deployment around cities, whatever its political advantages and its utility vis-à-vis Communist China, would be largely ineffective against the U.S.S.R. and, like pregnancy, hard to stop short of full term. And extensive ballistic missile defenses, while they could significantly reduce damage from an attack by those Soviet forces now in being or presumably programmed, could not reduce fatalities below several tens of millions-even if we struck first against the U.S.S.R. Should the Soviets choose to augment or upgrade their strategic strike forces, the net result could be, as Secretary of State Rusk pointed out, to reëstablish something approximating the present levels of mutual destruction at a much higher cost to both sides.

In the light of this gloomy prospect, the Administration is seriously trying to persuade the Soviets to limit their ballistic missile defenses-an effort upon which the U.S. Ambassador to Moscow, Mr. Llewellyn Thompson, is reportedly engaged. If he succeeds, then neither the improvements in strategic strike forces which the Department of Defense has programmed nor the partial deployment of anti-missile missiles around I.C.B.M. sites for which it has budgeted may be required-and many of the options previously discussed will seem irrelevant. However, it is doubtful whether even our able and influential Ambassador can persuade the Soviet leaders to accept a freeze on weapons, which would condemn the U.S.S.R. to continuing strategic inferiority. And any short-term moratorium on A.B.M.s will be really significant only if it is the prelude to a broader program of arms limitation, for otherwise the differing strategic concepts and conflicting strategic objectives of the two countries may impel either or both to procure ballistic missile defenses. Thus, one crucial question is the willingness of the United States to propose (and the Soviet Union to accept) new and far-reaching curbs on strategic armaments, now or in the near future.

IV

The content of any new proposals will depend in part on the importance attached to arms control in general and ballistic missile defenses in particular. From the preceding discussion it would seem that the introduction of anti-ballistic missiles-regardless of who introduces them and for what reasons-is likely to have a significant impact on the current negotiations for arms control. For instance, ballistic missile defenses, by injecting a new factor into strategic calculations and by triggering various responses such as those previously described, would necessitate a complete reorientation of our proposal for a freeze on strategic forces. And, since bombers may take on new importance as a hedge against ballistic missile defenses, the deployment of A.B.M.s would make bomber disarmament, whether total or proportionate, less acceptable and less likely.

In addition, the deployment of ballistic missile defenses could stultify progress toward a nonproliferation agreement. For one thing, the Europeans might view Soviet ballistic missile defenses as further degrading the effectiveness of our deterrent, and hence increasing the likelihood of Soviet pressures against NATO Europe. While a subsequent American deployment might somewhat strengthen belief in the credibility of the deterrent, it might also lead to greater European concern over the likelihood and the imminence of war, and thus to renewed efforts to buttress deterrence through the development of their own ballistic missile defenses or through control over nuclear strike forces. And should both sides deploy anti-ballistic missiles, the Europeans may again be concerned lest Europe become a battleground for the nuclear giants. While all conceivable reactions cannot be discussed here, it seems likely that the deployment of ballistic missile defenses by one or both sides will strengthen the desire of some Europeans to develop national or regional nuclear deterrents and increase their reluctance to sign a nonproliferation agreement.

In the longer run, the impact of ballistic missile defenses on the prospects for arms control may be even greater. At the very least, the requirement for hundreds or thousands of nuclear-tipped anti-missile missiles would militate against further cutbacks in the production of fissionable materials. Furthermore, the desire for greater information concerning warhead effects would make it difficult for either the United States or the Soviet Union to give up the underground testing of nuclear weapons, which, according to some reports, is related to the development of missile defense systems. And at some stage in the expenditure of billions of dollars, one side or the other might feel compelled to try out the operational effectiveness of its long-range antimissile missiles against incoming warheads. Even if these tests took place outside the atmosphere, so that there would be no fallout, they would constitute a clear breach of the present nuclear test ban, as would, of course, operational tests of nuclear-armed terminal defense missiles such as the U.S. Sprint or Hibex. Thus, in time, the procurement of ballistic missile defenses might lead to the abrogation or nullification of the nuclear test ban, as well as the inhibition of further progress toward arms control.

One reason for this is the probable effect on the negotiations themselves. As shown by the Soviet reaction to our intervention in Viet Nam, it is hard to reach agreement on arms control during periods of increased tension, such as would probably follow stepped-up expenditures for defensive and offensive strategic weapons. Moreover, increases in strategic armaments would certainly alienate those powers which are already seeking cutbacks in weapons stockpiles and strategic delivery vehicles as the price of their own adherence to any nonproliferation agreement.

At the very least, therefore, the deployment of anti-ballistic missiles would in all probability lead to a hiatus in arms-control negotiations, while both sides tried out their new weapons, decided on countermeasures to the other's deployment, and reestablished an effective and acceptable strategic balance. It could mean the loss of any chance for an early agreement on a comprehensive test ban and on the nonproliferation of nuclear weapons, leading to decisions by countries such as Italy or India to proceed with their own nuclear weapons programs. And it could lead to a new arms race with the U.S.S.R., in which, as Mr. McNamara put it, "all we would accomplish would be to increase greatly both their defense expenditures and ours without any gain in real security to either side."

In considering how the United States might attempt to hedge against these potential consequences, while still assuring its own security and protecting its own interests, a number of possibilities come to mind. The first and foremost, of course, is to seek at least a moratorium on anti- ballistic missiles-as we are doing-perhaps at the price of some change in the present levels of strategic strike forces. Failing this, we might seek agreement with the Soviets on measures to limit the numbers or types of ballistic missile defenses, or both, so that neither side would feel threatened by an open-ended deployment of such defensive weapons. Alternatively, the United States might try to set limits on the numbers or types of offensive weapons which might be added to the arsenals of both sides in response to the deployment of anti-ballistic missiles, in order to dampen the impact on the arms race of incremental increases in strategic strike forces. Indeed, we might find it desirable to suggest revisions in our present freeze proposal which would allow the limited introduction of antimissile missiles, providing corresponding numbers of I.C.B.M.s or I.R.B.M.s were destroyed.

To avoid interminable wrangling over technical details, and to allow for necessary adjustments in postures, such agreements might be tacit rather than formal, could be limited to a fixed number of years, or subject to cancellation for cause upon notice. The important problem is not the design of new measures, but recognition that reduction in armaments may promote the national security as well as-or better than-their augmentation.

It is obvious that judgments as to the desirability of building ballistic missile defenses will differ according to one's opinion as to the likelihood of war, one's desire to employ strategic forces as coercive instruments, one's theories on crisis behavior, and one's views as to how the communists are likely to conduct themselves in the next decade. But whatever views one may have on the utility of A.B.M.s, one must also acknowledge their disadvantages. For any deployment, the price, in coin and in new instabilities, will be high. Chief among the costs is likely to be an erosion of the already slim possibility of reaching agreement on further arms-control measures which could promote a more secure world. Without denying the importance of military power in attaining this goal, it is still possible to question the relative allocation of resources to the increase of that power, and particularly the addition of increments which promise so little and risk so much. On these grounds the whole issue of constructing ballistic missile defenses needs to be carefully thought through, by both the United States and the Soviet Union.

[i] Mr. McNamara has estimated that the best the Chinese could do, by 1975, would be to inflict six to twelve million fatalities on the United States; conversely, a small fraction of the U.S. delivery vehicles surviving a Soviet first strike could, if directed against China, kill fifty million Chinese and destroy half of Chinese Communist industry.

[ii] The New York Times, December 27, 1966, p. 9.

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