De-alerting of Nuclear Retaliatory Forces

De-alerting of Nuclear Retaliatory Forces


Richard L. Garwin

Senior Fellow for Science and Technology
Council on Foreign Relations, New York


IBM Fellow Emeritus
IBM Research Division
Thomas J. Watson Research Center
P.O. Box 218
Yorktown Heights, NY 10598

Tel: (914) 945-2555
FAX: (914) 945-4419
Email: RLG2 at

Member National Academy of Sciences
Committee on International Security and Arms Control
Adjunct Professor of Physics,
Columbia University)

November 20-22, 1997

Amaldi Conference


W353DNRF                       121997DNRF Final                       12/19/97


The ideal nuclear strategic retaliatory forces to some are none at all; but it may be some time, if ever, before world security will be enhanced by the elimination of all nuclear weapons, in view of the possibility that they might reemerge, to the disadvantage of peace-loving nations.

In the interim, it is in our interest to ensure that whatever nuclear weapons exist are securely in the control of responsible governments. Major reductions in nuclear weaponry are in order, and might be achieved bilaterally between the United States and Russia to a level of 2000 deployed strategic warheads; and in a post-START environment to a level of 1000 total warheads on either side. (1) However, in the interim we are faced with a situation in which there are vulnerable forces, especially in Russia, and vulnerable systems of command and control, so that the interaction between the two major nuclear powers is at least as unstable as during the Cold War. Because Russia, in particular, fears the loss of its command system, it is ready to launch its nuclear retaliatory force on warning of the launch of U.S. missiles; and the Russian warning system is far less capable than was the system of the Soviet Union.

Since 1962, U.S. nuclear weapons have contained a Permissive Action Link, associated with the nuclear warhead itself, which ensures that no nuclear detonation can occur unless a separate code is inserted into the warhead by the chain of command, independent of the firing of the missile or the dropping of the bomb. It appears that Russian nuclear weapons do not have such a closely integrated PAL, but in any case the PAL approach provides an example of the overall command that can be asserted over nuclear weaponry to avoid accidental or unintended launch. Similar techniques can be used to prevent a launch, to destroy a weapon before launch or after launch, and some are useful in what is usually called "de-alerting".

But as will be seen from the discussion, alert forces in general are motivated by their vulnerability and the vulnerability of the command system. The solution to the unintended launch that arises from a small perturbation in an unstable confrontation lies in rendering the forces less vulnerable, and that can be done at great cost by modification of a nation's own forces, but it can be done at lesser cost, in general, by modifications or change of status of the forces that threaten them.

The feared vulnerability of strategic retaliatory forces to a first strike from the other side leads to a posture of launch on warning, which increases the likelihood of inadvertent or unauthorized nuclear war. It is highly regrettable that strategic nuclear forces were given the accuracy to destroy silos on the other side, and equally unfortunate that the Soviet Union and the United States mounted MIRVs on their silo-based missiles. It should be clear that MIRVs do not pose a greater threat to the other side, for a given total number of warheads, but constitute a self-imposed vulnerability; one attacking warhead can be seen as destroying 6 or 10 MIRVed warheads in a single silo.

The combination of these two factors-- accuracy and MIRV vulnerability-- resulted in the theoretical possibility of the ballistic missiles on one side destroying the silo-based retaliatory force on the other side. For the U.S. MIRVed ICBM force (the Minuteman III), even this assumed vulnerability did not result in the elimination of the capability to retaliate, since the U.S. deployed also an invulnerable submarine-based force, but the situation was different for the Soviet Union. A much smaller fraction of the Soviet force (and now the Russian force) is deployed on SLBMs, and few Russian strategic submarines are at sea.

Most of the cost of strategic forces is incurred in reducing their vulnerability; neither the U.S. nor Russia will willingly allow their forces to be vulnerable, even in an era in which they do not regard one another as enemies.

The elimination of silo-based MIRVs in START II would reduce this vulnerability, but Russia would need to build 650 single-warhead silo-based missiles to benefit and come to parity with the U.S. in START II. Even if the Duma ratifies START II, there are years of vulnerabilty and resulting launch-on-warning posture for the Russian strategic forces in order to compensate for that vulnerability. And the hazard to both the U.S. and Russia is incalculable, as well as to the rest of the world.

The Russian warning system for strategic attack does not have the capability of the former Soviet system, since several of the long-range ballistic-missile warning radars are not on Russian territory. On the other hand, Russia says its missiles are no longer set on U.S. targets, and the U.S. states that its missiles are targeted on the oceans. As emphasized by Bruce Blair, (2) however, it would take seconds for the pre-planned targets to replace the non-targets in the missile guidance, and Russia has surely planned for that to happen if the missiles need to be launched on receipt of warning.

Of course, it would benefit neither Russia nor the U.S. to launch those missiles, but because they are considered vulnerable, they are maintained on LOW posture to deter intentional attack by the United States.

Taking only Russian missiles off alert would prevent their being fired before they are destroyed and would increase Russian strategic vulnerability; taking only U.S. missiles off alert would not create overall U.S. force vulnerability and so could not encourage a strike that would not otherwise have come, but it is unlikely be acceptable politically. In any case, only if the U.S. missiles were demonstrably incapable of being fired for some hours or more, would it be possible to take the Russian silo-based ICBMs off launch-on-warning status.

It is important to recognize that the off-alert status is beneficial only if the other side knows reliably when the weapons are being restored to firing capability and can then move to alert status, in the short term, or to reduced vulnerability-- for instance by moving mobile ICBMs out of garrison.

If missiles on both sides are demonstrably incapable of being fired, there is still the problem of competitive alerting. If one side can count on restoring its force to firing capability while the other is still off alert, then the de-alerting will never happen.


Before attempting to resolve this puzzle, consider some additional de-alert postures, besides the commonly cited separate storage of warheads from delivery systems. For example (3) one can enforce some hours of delay for silo-based missiles by covering the silos with 20 m of earth. Bulldozers or other earth-moving equipment nearby would need to remove most of this overburden if the silo cover is to be openable. The assurance of continued de-alert status can be conveyed by cooperative sensors on the earth heaps above the silos that give an "undisturbed" signal every minute or so, conveyed by satellite or telephone system and protected by the authentication system well worked out for the seismometers of the monitoring system for the comprehensive test ban treaty (CTBT).

The submarine-launched ballistic missile vessels (SLBM) might be sent to patrol out of range of their targets. Especially in a reduced-MIRV condition, however, the SLBM range may be so great that no large patrol areas can be found out of range of the targets; SLBM range can be reduced by fixing ballast mass in place of the offloaded MIRVs.

For the SLBMs in authorized de-alert areas (which can be very large), their presence within the agreed area can be verified by a cooperative system in which the verifying state transmits a coded request to the patrolling state, which forwards the request via its own communication means to the specified submarine claimed to be in the authorized patrol area. Call this particular submarine "B-143". B-143 comes to satellite communication depth within 30 minutes and prepares to receive a coded signal from a satellite at a precisely appointed time. It immediately recodes the signal and rebroadcasts it to that satellite and others that may wish to listen. It also broadcasts its position determined by GPS or GLONASS. The signals relayed to a processing computer on the verifying side then contain time-differences of arrival at the various satellites, that give an independent position determination of the patrolling submarine that should agree with the broadcast position. Since the signals can be timed to much better than a microsecond, and 1 km of displacement would correspond to some microseconds (for a speed of light or radio signals of 0.3 km per microsecond) the position of the coded receiver can be verified to far better than is required to ensure that the submarine is in the patrol area that will measure some hundreds or thousands of km in dimension. One must also ensure that the coded receiver remains with the submarine to which it is initially assigned and that can be done by wires or fiber-optic lines that are attached with disturbance-detecting magnets (or even durable self-adhesive tape) to the interior of the steel shell of the submarine. At the end of the draft paper, some preliminary thoughts are recorded regarding the vulnerability introduced by this occasional precise location of the submarine in the authorized de-alert patrol area, and proposals by others are requested.


An important goal, more readily achievable than assured de-alerting, is that of cooperative warning, in which under normal circumstances Russia would be assured of 30 minutes of warning of attack by U.S. ICBM warheads and 15-20 minutes from SLBM. Increasing the Russian confidence that U.S. missiles have not been launched is of vital importance to the U.S., in view of the reduced reliability and performance of Russian early warning systems. For U.S. silo-based ICBMs, this would be achieved by authenticated silo-cover monitors mounted on U.S. silo lids, that would broadcast every minute or so the fact that they had not been disturbed. Assurance of SLBM non-launch is more difficult to achieve, since the submarines, to maintain invulnerability by covertness, do not transmit radio signals regularly and certainly not every minute.

A more complex system of cooperative warning could be introduced that would invoke "destruct after launch" of any alert or re-alerted SLBM which had not received from its command authorities an authorization code to prevent self-destruction of the missile; the transmission of this message, by agreement enforced in hardware, would be communicated also to Russia. The authorization for launch of that specific missile might be valid only for a few minutes, as might have been previously agreed between the two sides; and no radio link to the missile would be needed-- only to the submarine or to the national command headquarters for communication to the submarine.

Other systems are possible and may be preferable. For discussions of post-launch controls (PLC) see articles by S. Frankel (4) and R.L. Garwin (5) The effect of the system sketched in this paragraph is to ensure that the launch of an SLBM is communicated immediately to the other side, or else it self-destructs after launch.

It is clearly in the interest of every nation to have secure control over its nuclear weapons, including post-launch controls. It is also in the interest of the international community. And it especially interests the U.S. that Russia have effective control over its strategic missiles (and Russia surely does not want one or more of its weapons to be fired without authorization or by accident). Hence it would be of value for the U.S. and Russia to collaborate closely on control and especially on Post-Launch Control, in an analog of the highly successful "lab-to-lab" collaboration that is improving Russian control over weapon-usable fissile materials; the U.S. should be willing to provide funds for the development and installation of PLC systems on Russian missiles, at the same time that it installs such on its own forces.

A quite different approach would simply share the output signals from the U.S. "Defense Support Program" (DSP) satellites, now called the Space-Based Infrared System (SBIRS). These satellites provide worldwide detection of missile launch by observing the intense infrared output from the hot rocket exhaust gases; during the 1991 Gulf War, SDIO leader Henry Cooper revealed that DSP had detected every SCUD launch from Iraq against Israel or Saudi Arabia. As with most of these cooperative measures, including de-alerting, if cooperation stops (so that assurance of de-alerting is no longer available, or if the output signals from DSP are no longer provided) the nations affected would need to reduce their vulnerability by resuming launch-on-warning postures, or on a longer time-scale by moving all missiles out of garrison, by deploying more SLBM at sea, etc.


Before any of these confidence-building measures (CBMs) are actually implemented by the nuclear nations, more analysis will need to be done by interested technical people. If solutions seem to be available, the nations concerned will no doubt request of their defense scientists a review of the validity and utility of the proposed measures. So it is useful both for those outside the defense establishments and for those who might later be involved in such analyses to consider seriously such approaches. In this first rough draft, insufficient attention has been given to at least two points:

There are other approaches that can be used, including the self-destruct after launch, unless proper commands have been received from the government, and these really merit serious study both by government and by independent organizations.

The value of such cooperative signalling approaches is the presumed greater willingness of the military and political leadership to undertake measures that do not require the transport of warheads during nuclear attack.


(1) "The Future of U.S. Nuclear Weapons Policy," report of Committee on International Security and Arms Control, National Academy of Sciences, Washington, D.C., National Academy Press, June 1997. Available at

(2) B.G. Blair, H.A. Feiveson, and F.N. von Hippel, "Taking Nuclear Weapons Off Hair-Trigger Alert," SCIENTIFIC AMERICAN, pp. 74-81, November 1997.

(3) R.L. Garwin, "Reducing Dependence on Nuclear Weapons: A Second Nuclear Regime," NUCLEAR WEAPONS AND WORLD POLITICS, see p. 100, (1977).

(4) S. Frankel, SCIENCE AND GLOBAL SECURITY, Vol 2, 1990, pp. 1-20.

(5) R.L. Garwin, "Launch Under Attack to Redress Minuteman Vulnerability?," INTERNATIONAL SECURITY, Vol. 4, No. 3, pp. 117-139, 1980.

(6) See also R.L. Garwin letter of 02/04/80 to Representative J.F. Seiberling, testimony for hearing of the House Interior Subcommittee on Public Land.

(7) S.D. Drell and R.L. Garwin, "Basing the MX Missile: A Better Idea," TECHNOLOGY REVIEW, May 1981.

(8) Soon be available at Tovish discusses at length the utility of timers for imposing delays on re-alerting.