Controlling Strategic Force Operations
As strategic forces are reduced to levels more nearly matching their core deterrent requirements and are reconfigured to make them less vulnerable to preemptive attack, it becomes increasingly important to regulate their operational practices as well. Force reductions and improvements in survivability promise to diminish incentives to initiate a strategic attack, but by themselves do not suffice to stabilize the interaction of deterrent forces, especially in times of crisis. In particular, these measures do not directly resolve the problems of stability that arise from the vulnerability of the underlying command systems.
Even modest numbers of nuclear detonations could seriously disrupt command and control systems. Additional investment in various methods of direct protection to reduce this effect have and should continue to be made, but the vulnerability cannot be entirely eliminated. As a result, existing U.S. and Soviet strategic command systems are prepared to perform their critical functions within the few minutes—30 or less—that would elapse between detection of the launch of a major intercontinental strategic attack and the initial nuclear explosions resulting from it.
With each of the opposing strategic organizations prepared for rapid retaliation, each must also assure itself that the preparations will not be susceptible to a catastrophic mistake. A policy based on deterrence inher
Page 41ently requires that assurance of reliable control be conveyed as credibly as the threat of retaliation. If one side ever interpreted the alerting procedures the other undertook as a protective precaution as decisive evidence of an impending attack, an unintended war might be triggered, with consequences well beyond any other imaginable human disaster.
The United States and the Soviet Union have devised weapons design principles and organizational procedures to assure both themselves and their opponents that deployed nuclear weapons will not operate unless instructed to do so. They have also deployed multiple warning systems designed to preclude any misjudgment by central political authorities. These provisions are a necessary complement to the many measures taken to assure that strategic forces will retaliate successfully if attacked. They have been successful for over 40 years in avoiding any actual or imminent explosion of a nuclear weapon. Assisted by an overriding political judgment that war is not in fact imminent despite the preparations that make it thoroughly possible, the warning systems have recorded and corrected numerous false indications of attack without ever approaching a catastrophic misjudgment or a breakdown of control. But the command structures of U.S. and Soviet strategic forces have never experienced the pressures of an intense crisis involving the simultaneous alerting of forces. While reassuring, experience to date cannot give definitive evidence about what would happen if a severe crisis altered operational routines and normal political judgments.
With accustomed patterns of evidence and inference disrupted, current warning systems could encounter serious difficulty in proving that an attack was not underway when the prevailing judgment began to suspect that it was. 1 The probability of that happening is presumably very low, but it can only be surmised, not demonstrated. This uncertainty and the enormous potential consequences argue that measures should be taken to strengthen reassurance as the problem of deterrence becomes less demanding.
In our view, four steps could help remedy this situation. The first is a continued program to improve the protection of the command and control system even while the forces are being reduced. The second involves fitting naval weapons with the devices commonly known as permissive action links (PALs) that have been used on other components of U.S. strategic force to physically embody authoritative political control. When installed, PALs make enabling the weapon or gaining access to the warhead itself dependent on receiving a special code from a higher command. The third involves cooperative measures that could increase the ability, if doubts ever arose, to prove that a strategic attack was not under way. The fourth involves a review of targeting practices to ensure that reductions in numbers of weapons systems do not lead to any questions about coverage of essential targets or to pressures for rapid reaction.
COMMAND SYSTEM PROTECTION
The operational measures for preserving confidence in core deterrence all depend on effective protection of the command system. This must continue to be a high priority for additional investments in strategic forces. Substantial improvements have been made in this regard over the past decade by using the basic methods of hardening, redundancy, dispersion, and reliability. Even greater progress could be made, however, if deterrence were recognized as the principal strategic problem and investments were focused on strengthening that objective. The command functions that are critical to enhancing confidence in core deterrence are much simpler than those required, for example, to manage a protracted nuclear exchange.
If the command systems could be given greater confidence that their core functions would survive the attack that even much smaller forces could carry out, or if they could be confident of reasonably timely reconstitution, then the danger of an explosive crisis interaction could be meaningfully reduced. There is no reason to believe that core deterrence would be diminished by such measures.
PERMISSIVE ACTION LINKS (PALs)
With the exception of sea-based systems, permissive action links have been incorporated in all U.S. nuclear weapons or weapons systems in order to provide additional assurance against their unauthorized launch. 2 The rationale for exempting the sea-based leg of the strategic triad rested on concerns that incorporating a PAL would compromise the dependability of our most survivable force by adding dependence on a communications link that a sophisticated adversary might be able to interrupt. It also recognized the unique nature of the SLBM weapon system, which requires the active cooperation of much of the submarine's crew in order to launch a missile.
Nevertheless, there are major changes in the nuclear relationship that now justify reconsidering the SLBM exemption. We propose a PALs concept for the SLBMs that would fail “armed,” that is, the PALs could have a mode in which it could be armed without the requirement for a message. In other words, successful jamming of communications links, after an appropriate time delay, could remove the PALs. This would effectively incorporate additional security against unauthorized launch at the possible expense of some effectiveness against time-urgent targets.
In Chapter IV, we recommended agreements with the Soviet Union to eliminate nuclear weapons from all surface ships. Until that goal is achieved, all sea-based nuclear weapons should be outfitted with PALs. Deploying PALs on all U.S. nuclear warheads should bolster U.S. efforts to persuade other nations to provide comparable control for all of their own nuclear weapons.
The judgment to withhold or to authorize strategic nuclear retaliation is supported by tactical warning systems designed to observe missile launches and aircraft flights. Under normal peacetime operations, the overall performance of the system has been highly reliable. The possibility that a strategic attack will be falsely perceived is considered negligible despite occasional errors produced by elements of the system. Since the system has never encountered a massed strategic attack, the possibility of its giving false reassurance under those conditions cannot be ruled out, but as long as the sensors are operating, that is also considered extremely remote.
There is inherently greater uncertainty, however, about intermediate conditions. The risk is that, in time of crisis, when an attack is perceived to be plausible, leaders will be persuaded to respond to poor-quality indicators of enemy attack. The alert procedures associated with a serious crisis could cause strategic force operations to vary substantially from normal practices, posing the risk that an attack could be initiated as a result of operations that are inherently difficult to detect and interpret.
Cooperative measures can be devised that would substantially strengthen the capacity of warning systems even in crisis. For missile silos, which currently house the strategic systems most likely to be used in the initial stages of an attack, cooperative devices can be designed that would transmit reliable indications that the missiles within had not been launched. For mobile missile forces, the problem is more demanding since their protection depends on concealing their exact location. Nonetheless, some increased reassurance might also be possible for these systems. The problem of designing cooperative warning indicators for aircraft and submarines would be substantially more difficult.
RESILIENT SECOND STRIKE TARGETING
At present, all available strategic weapons are assigned to targets according to a single integrated plan. The integrated plan assures systematic target coverage, meaning that forces are allocated to targets according to their perceived relative importance and that the highest priority targets are covered by two or more categorically different delivery systems. The plan also controls the relative sequence and timing of force operations in order to minimize mutual interference among the retaliating weapons and to assure that penetrating bomber missions are supported by prior missile strikes on air defense installations. The plan offers a wide variety of attack options within the context of a single menu. The menu itself is laborious to construct and cannot be rapidly altered, particularly if the command system that creates and disseminates it is damaged.
After detecting the launch of an attack, the authorization to retaliate must be disseminated and the choice of an attack option made from the available menu before the command system suffers too much damage. Otherwise, target coverage and operational timing could be severely compromised. The high priority given to destroying an opponent's strategic weapons also gives substantial impetus to rapid reaction since these missions must be accomplished before the opposing weapons are launched. The integrated targeting plan itself does not at present contribute to the inclination for rapid retaliation, however, since current strategic forces substantially exceed the numbers required for effective retaliation. There is so much redundancy for the coverage of priority targets that damage sufficient to deter is a statistical near certainty whatever the exact allocation of weapons might be.
As forces are sharply reduced and tailored more closely to the levels believed necessary for deterrence, the details of operational coordination and of allocating warheads to a smaller number of targets become more important. This effect should not and need not be allowed to lead either side to adopt a posture that relies on prompt retaliation for deterrence in order to avoid operating with a damaged control system. The problems associated with more effective allocation of resources after an attack are difficult and this is not the place to discuss them in detail. We simply note that opportunities exist to mitigate the problem, for example, by giving weapons systems a suitable targeting option beforehand. Using statistical procedures for assigning weapons to targets and assuming survival rates appropriate to the particular weapons system concerned, a high degree of confidence that the highest priority targets will be covered can be assured, and operational interference minimized no matter which particular weapons systems escape destruction. ( Appendix C contains a fuller discussion of this point.) This could also be done after an attack has taken place, if the command, control, and communication system is capable of assessing the survival rates, but the returns may not warrant the added complications and risks.
1. B.G. Blair and J.D. Steinbruner, The Effects of Warning on Strategic Stability, Brookings Occasional Paper. Washington, D.C.: The Brookings Institution, 1990.
2. D.R. Cotter, “Peacetime Operations: Security and Safety,” in A.B. Carter, J.D. Steinbruner, and C.A. Zraket, Managing Nuclear Operations. Washington, D.C.: The Brookings Institution, 1987, p. 51-52.