This text is from Strategic Survey 1977, published by the International Institute for Strategic Studies in London at the end of May. It appears in the chapter on “New Factors in Security.”


In recent years there has been increasing concern in the West about the future stability of the global strategic balance. The counterforce capabilities of both the United States and the Soviet Union are improving significantly, threatening the survivability of fixed strategic installations and challenging the role of the land-based components of national deterrent forces. By the mid-1980s deployment of the new technologies now being developed will seriously erode the second-strike capability of land-based missiles.

Although much of the recent debate has centered on this question, it may by then no longer be relevant. Not for many years has technological change been as volatile as it is at present. With many applications of new technologies under development, others “in the pipeline,” and still more being researched, it can no longer be assumed that the premises upon which the present strategic stability are based are assured.

Recent Developments

Of primary significance for the future of the strategic balance, at least in terms of the next ten to fifteen years, are a number of developments in strategic technologies—in engines, warheads, and guidance systems.

The greatly enhanced precision-guidance capacities which are now, or soon will be, available offer extraordinary accuracy. These guidance systems use for homing either those characteristics of a target which distinguish it from its surroundings (e.g., optical, infra-red, radio-wave, or acoustic signatures) or highly accurate navigation to strike fixed targets with known locations (or passing known locations) by such means as terrain contour matching (TERCOM), advanced inertial navigation systems, or navigation satellites.

Although both the United States and the Soviet Union have made progress in this field, American ballistic-missile guidance systems are generally considered to be a generation ahead of their Soviet counterparts. Judging from the varying estimates of accuracy that have been given, the current circular error probable (CEP) of the Minuteman III ICBM seems to be as low as 600-800 feet. Software improvements in the NS-20 guidance system, now being incorporated in all Minuteman III, will reduce this margin even further. The advanced inertial reference sphere (AIRS), a 10.3-inch diameter gimbal-less inertial guidance system being developed for the US Air Force’s MX ICBM, is expected to produce a CEP of around 200-300 feet, the lower figure probably being the limit attainable with purely inertial systems.

Although the United States is investigating the application of various techniques of terminal homing to ICBM, it seems doubtful, given these very low CEP, that they will increase accuracy enough to justify their deployment. By comparison, the CEP attributed to the latest generation of Soviet ICBM—the SS-17, SS-18, and SS-19—range from about 1,200 to 1,600 feet and are not expected to come below 1,000 feet until the early 1980s.

Increasing accuracy is also a feature of the American submarine-launched ballistic missile (SLBM) systems. The CEP of the Poseidon SLBM is currently about 1,500 feet at its maximum range of 2,500 nautical miles, and the Improved Accuracy Program (IAP) is expected to reduce this to about 1,000 feet by the early 1980s. The Trident I (C4) missile, expected to be operational before the end of this decade, will carry a full payload 4,000 nautical miles while maintaining accuracy equivalent to that of the Poseidon missile, primarily by using a stellar sensor to take a star sight during the post-boost phase of the missile flight to correct the flight path. It is, of course, not necessary for this missile to be launched over its maximum range, and shorter flight paths produce correspondingly lower CEP: a Trident missile with a CEP of 1,200 feet at maximum range would have a CEP of under 1,000 feet if limited to the range of the existing Poseidon SLBM.

These low CEP give existing and forthcoming American SLBM a substantial capability against all but the most hardened military targets; furthermore, the introduction of the Trident II (D5) missile, planned for the late 1980s, would give the American SLBM a true counterforce capability. Soviet SLBM—including the SS-N-8, which has a range of nearly 5,000 nautical miles and uses a stellar inertial guidance system—are reported to have achieved CEP of under 1,500 feet, giving them a marginal counterforce capability.

Several important research and development (R&D) projects on propulsion are on the verge of yielding greatly improved efficiency in the use of fuel, weight, and space. They include improved solid-propellent rocket booster motors and relatively small but highly efficient turbo-fan and turbo-jet engines—for use in, for example, strategic and tactical cruise missiles. While developments in modern guidance systems, and particularly “area correlation” techniques such as TERCOM, have excited strategic analysts and planners the most with regard to cruise missiles, they could not have been fully utilized without the development of small (100-150 pound) engines capable of powering missiles over a range of 600-2,000 miles.


The technology of explosives and warheads has also changed greatly in recent years. Not only has the destructive potential of a given warhead volume and weight increased, but a variety of new warheads have been developed to meet specific requirements, particularly for theater use. The United States has developed the B-61 variable-yield (“dial-a-yield”) bomb; the three-choice fullfusing option bomb with a device which, at the discretion of the bombardier, enables detonation of the freefall bomb either in the air, on impact, or by delayed action; a series of low-yield nuclear artillery shells for the 155mm and 8-inch guns of the US Army in Western Europe; and the enhanced radiation or neutron bomb.

This increased ability to control the timing, size, and type of explosion will permit greater use of these munitions where considerations of the safety of one’s own troops or population centers become paramount. Although the applicability of these developments for strategic nuclear use is less clear, they have the potential to increase further the options in scenarios of counterforce and limited strategic warfare. A range of conventional explosives and warheads with potential strategic implications have also been developed recently. It is possible that non-nuclear weapons, including fuel-air explosives, improved cluster munitions for area targets, and hard structure munitions, when combined with highly accurate, long-range ballistic or cruise missiles, could be used against targets which can now be destroyed only by nuclear weapons.

Other technological developments, although outside the sphere of weapons, may also affect the strategic balance: developments in command, control, and communications (C3) technologies (including real-time satellite observation and warning), considerable improvements in data processing, and retargeting capabilities for both ICBM and SLBM systems. All three have greatly increased the ability of both the US and the USSR to launch strategic nuclear strikes of a very limited and selective nature, so as to permit the fighting of an extended war involving controlled sequential exchanges.

Although the United States has possessed a rather extensive capability for such controlled strategic warfare since at least 1961, Soviet developments are much more recent. It was not until July 1974 that the Soviet Union was able to launch her first geostationary satellite, and she now has at least two military communications satellites operating at geosynchronous altitude. An over-the-horizon radar system (which began test transmissions in July 1976) is being developed as an alternative long-range early-warning system. Hardened command and control installations have purportedly been constructed both in the Moscow area and within ICBM deployment fields.

Interestingly, the introduction of a new technology for crisis prevention—the Moscow-Washington satellite hotline—even provides for continuous communication between the White House and the Kremlin during a nuclear exchange, thus making a controlled nuclear war on a limited level feasible. It should be noted, however, that these supportive systems providing flexibility to existing nuclear forces are themselves vulnerable. Many of them—early-warning radars, communications links, the very-low-frequency command system of the ballistic missile submarine fleet—are large and easily attacked. Their destruction would not only rule out further controlled exchanges but would also seriously affect certain strategic capabilities.

American counterforce capabilities would suffer most in this respect, since American ability to attack hard targets and the associated American strategic policy of target discrimination is much more dependent upon supportive systems than upon the large throw-weights that Soviet designers prefer. To the extent that actual war-fighting scenarios become increasingly accepted, one can expect further hardening or protection of these potential subsystems of control against nuclear weapons effects.

Implications of Available Technology

The collective impact of more accurate, powerful, and discriminating offensive weaponry has two major implications for the maintenance of strategic stability. First, the continued viability of a basic component of contemporary strategic forces—fixed-site land-based missiles—has been called into question; second, the greater theoretical ability to fight a strategic nuclear war at controlled levels may increase pressures to launch a preemptive counterforce strike in a crisis.

These developments are principally a result of the very high single-shot kill probabilities (SSKP) which can be achieved by ballistic missiles with the high accuracies described above. Even against targets hardened to withstand 1,000 psi blast overpressure, the present Mk 12 re-entry vehicle of the Minuteman III (with a 179KT warhead) could achieve an SSKP estimated to be between 45 and 60 percent with a CEP of 700 feet. By comparison, the Mk 12A warhead (designed to replace the Mk 12), with its 350KT warhead and a CEP of 500 feet, is expected to have an SSKP against the same target of up to 90 percent.

More significantly, an American decision to deploy a force of 300 MX ICBM would give the United States a first-strike potential of destroying well over 90 percent of the fixed land-based Soviet missiles. Before that time—by the mid-1980s—improvements in the accuracy of Soviet ICBM will give the Soviet Union the ability to destroy a substantial proportion of the American ICBM force. However, since a greater proportion of Soviet deterrent forces consists of ICBM than is the case for the United States, ICBM vulnerability will have a greater impact on the Soviet Union than on her Western rival.


Yet at the same time that technology has increased the vulnerability of these missiles, it has also provided options which either increase their survivability or provide alternative choices for strategic forces. One possibility is to accelerate the hardening of ICBM silos, so as to reduce their vulnerability to attack. About half the present American ICBM force is hardened to withstand about 1,000 psi blast overpressure, and a number of the new Soviet ICBM are reportedly being deployed in 2,000 psi silos. But silo hardening has its limits. In normal engineering practice, the maximum compressive strength of concrete is estimated to be 3,000 psi. Such hardening is very expensive (a 3,000 psi silo costs more than $15 million) and is feasible only in special geological environments. More important, if missiles with CEP as low as 600 feet are used, hardening to 2,000-3,000 psi reduces SSKP by only a few percentage points.

A second and much discussed means of reducing the vulnerability of land-based missiles is to make them mobile. The Soviet SS-16 ICBM was designed for land mobility, and the SS-20 IRBM (which comprises two stages of the SS-16) is already operational in a land-mobile mode. In the United States, the MX ICBM, if approved, will probably be deployed in some mobile form, although the specific configuration remains to be decided. Primary basing concepts now being considered for the MX consist of concealing mobile missiles in either underground trenches or multiple hardened shelters. But while the MX offers an apparently useful technical response to the threat posed by the new generation of offensive Soviet missiles, it also promises to be controversial. Not only will the cost be considerable (about $30 billion for the program, comprising 300 MX tunnel-based mobile launchers), but the system, although less vulnerable than fixed ICBM, may still not be absolutely invulnerable to an accurate Soviet strike with high-yield warheads. Moreover, the introduction of an American mobile system might accelerate the Soviet move to mobility on a much wider scale, thus making verification of any arms-limitation agreement highly imperfect.

A third response option is to adopt a launch-on-warning (LOW) strategy, which calls for launching one’s own offensive missiles as soon as radar confirms that the adversary has launched his. This would remove the need for survivable systems, or redundant systems in order to ensure sufficient retaliatory, second-strike capability. However, nearly all analysts reject LOW as inherently destabilizing and lacking credibility. It is argued that a LOW posture would increase the potential for accidental war, while at the same time placing difficult if not impossible pressures upon decision-makers in times of crisis. More feasible might be a launch-through-attack (LTA) strategy: missiles would be launched when the full scope of the attack became clear. But the utility of an LTA posture diminishes as the synchronization and the success of the attack rise, and it remains a highly risky solution to ICBM vulnerability.

Before any of these responses is seriously considered—and none of them is either cheap or foolproof—it will be important to put the emerging vulnerability of land-based strategic missiles in perspective. Much of the American debate on this issue has tended to draw strategic consequences from technological capabilities: because ICBM are becoming more vulnerable, it is argued, the Soviet Union could see an advantage in destroying them, thus leaving the United States in an inferior strategic position from which to respond. For both political and technical reasons, this is a scenario of questionable plausibility, and thus does not provide a basis for serious assessment of the significance of ICBM vulnerability.

First it assumes that the United States will indeed recognize a massive Soviet attack on her land-based missile installations as a limited—as opposed to an all-out—nuclear strike and will be willing to respond only in kind. In his FY 1979 Defense Posture Statement, however, Secretary Brown cast doubt on this assumption: “The Soviets might—and should—fear that, in response, we would retaliate with a massive attack on Soviet cities and industry.”

Second, such a strike only makes sense if the attacker has complete confidence in the reliability of his counterforce systems and can be assured that a complex coordinated salvo at intercontinental range will work to perfection. Phenomena such as “fratricide” (exploding warheads creating an environment in which other incoming warheads do not function properly) must reduce confidence in any such projection. Secretary Brown also raised this question in the Posture Statement, arguing that “the Soviets would face great uncertainties” in planning a first strike, and “they must recognize the formidable task of executing a highly complex massive attack in a single cosmic throw of the dice.”

Most important of all, constantly deployed submarines (SSBN), bombers, cruise-missile carriers, besides surviving ICBM, would provide a retaliatory or second-strike capability for considerable counterforce, as well as for all-out, response. By the mid-1980s, the United States can expect that over 6,000 warheads will survive a surprise Soviet first strike—and perhaps as many as 10,000 if she were on full alert before the attack. Despite the unquestioned fact of growing ICBM vulnerability, a more sober assessment of its implications is needed before decisions can be taken on the most suitable response.

The Dimmer Future

Technologies affecting land-based missile vulnerability are not the only qualitative developments affecting strategic stability. By the time that this vulnerability becomes a reality, it may no longer be the crucial issue in determining what is an effective balance of deterrence. Potentially even more influential are technologies being researched and developed that could affect the survivability of satellites and submarines, and (most fundamentally) the ability of offensive missiles to penetrate to their intended targets.

To date, greatest attention in this area has been given to satellites and the growth of anti-satellite satellites which can interfere with verification and reconnaissance, early warning, and C3. During 1977, the Soviet Union continued her program of actively testing interceptor satellites, bringing the total number of tests to fifteen, of which eight involved maneuvering the interceptor near the target satellite, which was then destroyed by the “explosive destruction” of the interceptor. One Soviet test in 1977 involved intercepting a target satellite at an altitude of over 620 miles—a capability which, if perfected, would threaten the US Navy’s transit navigation link. However, the Soviet Union has yet to demonstrate a capability to intercept satellites at higher altitudes—essential if the geostationary satellites at 22,300 miles critical to American early-warning and C3 functions are to be made vulnerable.

The United States has responded to the Soviet effort by beginning her own anti-satellite program, based on the principle of destroying the target satellite by collision. The first tests of this American hunter-killer satellite are scheduled for 1980, and an initial operational capability is set for 1982. At the same time, the United States is improving techniques to counter Soviet advances in anti-satellite weaponry. These steps include increasing the protection of sensitive components in satellites, the development of detection and evasion capabilities, and even the use of lasers to destroy enemy interceptors. (Both countries are exploring the use of lasers and charged-particle beams to blind or destroy each other’s satellites.) A third American response is political rather than technical: the proposal first made in March, that negotiations should begin to control the development and deployment of this new category of anti-satellite weaponry, so as to nip this newest “space race” in the bud.

Less advanced, but of equal if not greater potential significance for strategic stability, are R&D efforts in anti-submarine warfare (ASW). Although no breakthroughs have occurred or seem imminent, the United States continues to make progress in her mostly acoustic ASW program. More speculative and exotic are several Soviet investigations into various “hydrodynamic signatures” (including heat, radiation, gas, magnetic, and wave) made by passing submarines and potentially detectable by satellites, surface ships, and other submarines. These efforts notwithstanding, the basic ASW problems of detection and destruction remain formidable. In addition, the increased range and reduced noise and cross-section of the new generation of American SSBN will increase the problems facing Soviet ASW experts, as will the establishment of new C3 procedures (notably the planned extremely-low-frequency Seafarer system), which will eliminate the need for submarines to reduce speed and approach the surface to communicate.

No single technological breakthrough would be as far-reaching as the development of a viable ballistic missile defense (BMD). The introduction of a comprehensive BMD system would undermine the fundamental “deterrence through mutual vulnerability” concept of contemporary strategic stability. The 1972 ABM Treaty between the Soviet Union and the United States effectively prohibits the deployment of BMD, both of then-existing and future technologies, and is of indefinite duration. But the Treaty does permit continued research and development, and there are indications that Soviet and American R&D programs continue unabated.

The most interesting avenue of research involves generating streams of charged, subatomic particles and directing them with electromagnets at a target. While theoretically such charged-particle-beams could be used to destroy incoming missiles, certain basic problems exist: the earth’s atmosphere is difficult to penetrate, and its magnetic field interferes with guidance. The technology is still primitive, and the allegations of General Keegan and others that the Soviet Union has had considerable success in this field are premature. All the same, the potential development of a BMD system based on charged-particle beams or an alternative technology is a disquieting prospect.