Option 4. Unrestricted Competition
The most troubling alternative to some form of agreed transition or to a postponement of any final decision about such a transition is unrestricted competition in both offensive and defensive weapons. The consequences, as McNamara points out, would be very serious:
A unilateral shift to Star Wars would have disastrous consequences. The ABM Treaty, the most important arms control agreement of the nuclear age, would be the first casualty. Because of the resulting race in strategic defense weaponry, each side would begin to build up its offenses to ensure deterrent capability. Thus, the existing SALT agreements would be the next casualty. Future accords to restrain the offensive arms competition would be impossible until the Star Wars race was halted and reversed.
In strategic terms, any decision by either side to proceed unilaterally to violate the ABM Treaty (not in some specific way—as the Soviets did in the case of the Krasnoyarsk radar—to take advantage of a loophole without affecting the general aim of the treaty, but in a way that would undermine the treaty in an essential way by producing a territorial defense
or even a major defense of missile silos) would certainly be read by the other side as a commitment to achieve military superiority, either to prepare for a preemptive strike or simply to be in a position to harvest political benefits. Such an effort would be met by a concerted effort on the part of the other side to match the buildup or, possibly, to defeat the defenses. During such a competition, both sides would have reason to fear that their retaliatory deterrents could be put in jeopardy. Under the circumstances, there would be both crisis instability and arms race instability.
If both sides were to deploy space-based defenses using speed-of-light weapons, the temptation to strike first, in a counter-defensive mode, would be greater than it is in a condition of offensive mutual deterrence. Under such circumstances the stage would be set for what a Senate staff report called "a 'high noon' shoot-out in space." Each side would have to recognize that the first to shoot would win, unless—as is highly unlikely—weapons and sensors can be made undetectable or invulnerable. Directed-energy weapons will very likely be even more effective against satellites, including those that would carry strategic defense sensors and weapons, than they would be against ballistic missiles. Although such a conflict would not itself involve the use of nuclear weapons, it could easily lead to their first use by the side whose defenses were under attack, if that side should become convinced that it was being put into a situation in which it must either "use them or lose them."
Those in favor of SDI nevertheless argue that whatever response the Soviet Union might make, the United States would have an advantage in military technology and could exploit this advantage to develop defenses that would be so cost-effective that the Soviets would have no choice but to recognize that their offenses had indeed become "impotent and obsolete." Meanwhile, of course, the United States would continue to rely on its offensive deterrent to forestall any Soviet preemptive attack. But this argument falters on the issue of cost. It is easy enough to postulate that the United States can develop defenses while maintaining a potent retaliatory force, but given that an effective defense would have to include a layered screen capable not only of intercepting virtually all ballistic missiles fired at the United States and its allies—whether from long-range or short-range weapons—but also as air-launched cruise missiles, bombs, and standoff weapons, such a defense is bound to be extremely costly; vast sums must meanwhile be spent on keeping offensive forces up to date. The possibility that the Soviets would shift to a policy of emphasizing conventional war, perhaps conducted by proxies,
against vital U.S. interests, or that other threats would develop (like that posed by Khomeini's Iran in the Persian Gulf) would force the United States to spend possibly even more than it now spends on conventional military forces. That a defense transition would be feasible under these circumstances altogether ignores the pressures for trade-offs among military options as well as the pressure exerted during peacetime on the domestic budget. A strategy that is not affordable and is not likely to be sustained politically is one that cannot be maintained in either strategic or economic terms.
A strategy must also take into account the psychological and other effects on the structure of alliance in which the United States plays a leading role. To the extent that SDI has already aroused misgivings among U.S. allies, because it seems to endanger the process of arms control and détente, a decision to proceed beyond the present research stage into development and deployment would risk gravely exacerbating these fears, quite possibly arousing such political opposition as to bring about the collapse of the alliance. The alliance has been held together for four decades on the assumption that the nuclear shield would serve as a deterrent against Soviet aggression. The abandonment of that nuclear shield in favor of a defensive system in which the allies have no confidence, and which might trigger Soviet counterefforts against them could strengthen the current trend to regard the Soviets as less of a threat to Europe than the United States. A strategic revolution of the kind implied by the idea of a defense transition can be promoted unilaterally only at great peril to the alliance. This is especially the case inasmuch as West Europeans are likely to fear that if both superpowers achieve even reasonably effective strategic defense not only would the independent deterrents of France and Britain be nullified but also the way would be open for the U.S.S.R. to exploit what is perceived to be its advantage in conventional force in Europe.
The issue of strategic defense also runs into the problem posed by the possible resort to conventional force. Although both sides have maintained considerable conventional forces and both have brought these forces into play in military engagements—the United States notably in Korea and Vietnam, the Soviet Union in Czechoslovakia, Hungary, and Afghanistan—they have been inhibited in the use of conventional force in situations that could lead to direct confrontation and escalation to the use of nuclear weapons. In that sense, nuclear weapons have had an inhibiting effect on the actual or threatened use of conventional force. To the extent that that option or danger is removed, would the world be
made safe once again for conventional war? The U.S. guarantee of extended deterrence for its allies would be rendered meaningless, because it rests not on its ability to help Europe to deter a Soviet attack by providing conventional support but on its "nuclear umbrella."
Even now, Western Europeans doubt whether they can rely on the U.S. nuclear guarantee. They wonder whether, despite formal commitments, a U.S. president would risk the safety of the United States by ordering a nuclear strike against the Soviet Union to defend Europe. Those who express this doubt often argue that NATO should be better prepared to check any Soviet aggression by conventional means in order to minimize the need to rely on the threat of U.S. nuclear forces. For the same reason, two European states, Great Britain and France, have felt compelled to develop independent nuclear deterrents. If these were nullified, the conventional threat would indeed become more serious.
If the conventional threat became more serious, however, the West Europeans could be expected to take the case for conventional armament more seriously. Until now, they could avoid taking the hard decision to increase spending and to devote more manpower to the defense of Europe by relying on the U.S. nuclear guarantee. If they could no longer rely on such a guarantee, they might simply have to respond by building up conventional defenses. This will become more and more difficult as the Soviets acquire more accurate conventional weapons with which to strike at NATO airbases and command facilities, but it is certainly not impossible for the West to build up its conventional forces to an extent that could deter the Soviets or to negotiate asymmetrical reductions.
Outside Europe, the U.S. nuclear shield is even more dubious. The United States may formally pledge to defend the vital interests of the West by any military means necessary, but the unwillingness to rely on nuclear weapons led to the Carter administration's creation of the Rapid Deployment Force, a move reinforced by the Reagan administration's decision to create a new command for mobile and swift intervention. Although the defense of Japan and South Korea also involves the nuclear option, here, too, conventional force deployment is seen as a vital complement to a credible defense. It is not obvious that the elimination of the nuclear umbrella would necessarily place these allies at greater risk, or that the risk could not be kept minimal by the deployment of greater conventional force.
In Europe and other theaters, significant expansion of conventional forces would entail costs, but these could be shared with allies who can
now well afford to contribute more to their own defense. The costs are therefore not a significant deterrent to a shift to greater reliance on conventional forces. Nevertheless, it would remain possible that the deterrent effect of conventional forces would be far smaller than that created by nuclear weapons. There have been major wars not involving the superpowers—in the Middle East, for example—in which the sides were not inhibited from going to war because they did not fear nuclear attack. It is at least conceivable that in Europe or the Far East, either side might be prepared to enter a conventional conflict to achieve some limited objective. War, in other words, might become more "thinkable" among the superpowers than it has been since both acquired the means to deliver great numbers of nuclear weapons.
For this reason, the abandonment of the strategy of deterrence by the threat of retaliation in favor of the development of assured defense—always assuming such a defense is possible—could indeed increase the danger of conventional war. This danger is compounded, as previously noted, if the atmosphere is characterized by mutual mistrust and there are no constraints on the development of military forces of all types. The effort to develop defenses against conventional attack may succeed in allaying some of the difficulty, but there is little reason to suppose that such defenses could be good enough to forestall conventional wars altogether, under favorable circumstances.