Volume 23, Number 4 October 1994


Symposium on Theater Ballistic Missiles: What Is the Threat? What Can Be Done?

Physics and Society presents here papers based on four of the five talks given at the invited session on Theater Ballistic Missiles, held at the APS meeting in Washington, DC, on 18 April 1994. Lisbeth Gronlund presided over the session. The fifth paper, "Arms Control Options for Ballistic Missiles" by Lora Lumpe, could not be published in this issue due to space limitations; it will be published in the next (January 1995) issue.

Previous Experiences with Ballistic Missile Attacks and Defenses

George N. Lewis In considering the threats posed by ballistic missile proliferation and possible responses, it is useful to begin by reviewing previous ballistic (and cruise) missile attacks. Here I will focus on the best documented cases: the German attacks on Britain and the Iraqi attacks on Israel.

The German V-1 and V-2 attacks on Britain

From June 1944 until March 1945, Germany fired about 1400 V-2 ballistic missiles and nearly 10,000 V-1 cruise missiles at Britain. An additional 2000 V-2s and 12,000 V-1s were fired at targets in continental Europe, primarily the port of Antwerp.

The V-2 was a ballistic missile with a range of about 275 km and a warhead containing about 750 kg of high explosive; these characteristics are very similar to those of the Scud-B that is widely deployed today. The V-1 was a cruise missile--essentially a small, pilotless airplane--with a range of about 230 km. It was launched either from a fixed catapult or from an airplane, carried an 850 kg warhead, and flew at speeds of about 550-650 km/hour at a typical altitude of 600-1000 meters.

Both missiles were so inaccurate that they were only suitable for attacking large urban targets, and London was the primary target. The two missiles did roughly equal damage per missile to structures. On average, each missile reaching London destroyed 10 houses and seriously damaged another 60.

Of the 1400 V-2 ballistic missiles fired at Britain, 1055 actually reached it. 518 landed in London, killing 2510 civilians (all V-1 and V-2 casualties cited here are for civilians only; if military personnel were included, the figure would be roughly 5-10% higher). 537 V-2s landed elsewhere in Britain, killing another 240 people. Of the nearly 10,000 V-1 cruise missiles fired at Britain, about 2420 hit London, killing 5370 people, and another 3200 hit elsewhere in Britain (many of these were shot down), killing another 470. Taken together, the V-1s and V-2s accounted for about 15% of all deaths due to bombing in Britain during World War II.

On average, each V-2 reaching London killed about 4.8 people while each V-1 killed about 2.2. The lower casualty rate for the V-1s was primarily due to the warning for the V-1 attacks--V-1s could be detected by radar and approaching V-1s could be heard, and often seen, from the ground. In contrast, there was no warning of V-2 attacks, since the supersonic V-2s could not be heard prior to impact. Although some V-2s were detected by radar, this detection capability was not sufficiently timely, reliable and accurate to warn to the public.

There were no effective defensive measures against the V-2, aside from the partial evacuation of London. It was not feasible to shoot them down in flight. On the other hand, using a combination of fighters, anti-aircraft guns, and barrage balloons, the British were able to destroy a significant fraction of the V-1 cruise missiles in flight. The shoot-down rate varied from about 30% early in the attacks to better than 70% towards the end of the attacks.

Britain, together with the U.S., devoted substantial resources to V-1 and V-2 defense, with relatively little success. During the 13-month peak of this effort, 14% of the bomber sorties and 17% of the tactical air forces missions from Britain were devoted to countering the V-weapons.

Well before the missile attacks began, the allies launched air attacks on the missile production, storage, and launch facilities. The V-2 development center at Peenemunde was bombed in August 1943 (and several times subsequently), but the development of the missile was nearly complete by then, and at most a few months delay was achieved. Several large, fixed V-2 launch facilities were bombed and destroyed. This had essentially no effect on the missile attacks, however, since V-2s were launched by mobile launchers at a rate essentially limited by supply. Once the V-2 attacks began, fighter and fighter-bomber sweeps of suspected launch areas were carried out, but also with little success.

Prior to the use of the V-1s, the allies attacked and largely destroyed the original network of launch sites the Germans were preparing. However, by the time the V-1s were ready to be launched, the Germans had developed a new network of more modest and better camouflaged launch sites. Although allied air attacks destroyed some of these sites, no effect on the V-1 launch rate was observed.

Bombing attacks on production facilities were also carried out. However, subcomponent production was dispersed and assembly was underground, and these attacks had little effect. The overall strategic bombing campaign probably indirectly affected production--the US Strategic Bombing Survey estimated a 20% reduction in total production. However, the V-1 and V-2 attacks continued until the allies occupied their launch areas with ground forces.

The V-1 and V-2 missile attacks failed to achieve their objectives (primarily that of persuading Britain to abandon the war) or to significantly affect the outcome of the war. Moreover, the V-weapons were a serious diversion of German resources. The U.S. Strategic Bombing Survey estimated that the resources devoted to V-weapon production were equivalent to that needed to produce 24,000 fighter aircraft.

The 1991 Gulf War

During the 1991 Gulf War, about 80 al-Hussein missiles fired by Iraq fell in or near Israel or Saudi Arabia. The Iraqi missiles--which were similar or identical to the missiles used against Tehran in the War of the Cities--were quite inaccurate, with a CEP of at least several kilometers.

I will focus on the attacks on Israel, because of the better quality of that data. Roughly 39 Scuds--the majority fired at Tel Aviv--landed in or near Israel, although about half fell in the Mediterranean or short of Israeli cities. These Scuds directly killed 2 people (11-12 other people died from heart attacks or improper use of gas masks) and caused 11 moderate to serious injuries and 221 light injuries. To put these figures in perspective, deaths from all causes in Israel during the period of the Gulf War were 4154--somewhat below average for that time of year.

It is immediately apparent that the consequences of the missile attacks--both overall and on a per missile basis--were very different in Israel and London. Based on the V-2 experience in London, after scaling for the higher population density of Tel Aviv and the smaller warhead of the Iraqi missiles, 3.3 deaths and 8.0 serious injuries would be expected per Scud falling in Israeli metropolitan areas. However, on average, each of the roughly 20 Scuds falling in Israeli metropolitan areas caused only 0.1 deaths and 0.6 serious injuries--a death rate lower by a factor of 30. What accounts for this difference?

Although the Patriot air defense system is often credited with reducing the casualty rate in Israel, it actually at best played a relatively minor role. At least 22-23 Scuds fell into areas defended by Patriot, with at least 6 of these falling before Patriot was operational. For the 16-17 Scuds that were engaged by Patriot, the U.S. Army claims a success rate of about 40%--or 7 Scuds successfully engaged. However, all independent reviews of the Army's still-classified data indicate that the Army's data is inadequate to back up its claims, the only independent analysis of Patriot's Gulf war performance concluded that its performance was much poorer than the Army is claiming, and the still-classified Israeli assessment concluded that there was at best circumstantial evidence for one successful engagement. Nevertheless, even if one accepts the Army's claim, it is clear that a roughly 7/22 = 32% reduction in Scuds striking Israeli cities could at best explain only a small part of the observed 3000% reduction in the per-missile death rate compared to the V-2 experience in London.

This conclusion is supported by the available damage and casualty data from before and after the Patriot deployment in Israel. Of the approximately 39 Scuds reaching Israel, 12 fell before Patriot was operational and 27 after. On a per missile basis (excluding the 8 Patriot missiles that dove into the ground in Israel), deaths, injuries, and light damage to apartments all increased after Patriot was operational, while heavy damage to apartments may (depending on how one counts the missiles) have decreased slightly. However, none of these increases or decreases are statistically significant--one can only conclude that any effect of Patriot on casualties is lost in the statistical noise.

What other factors can explain the relatively low casualties in the missile attacks on Israel? First, the Scuds were very inaccurate. Only six actually fell within Tel Aviv. In addition, several did not explode--including one that directly struck a multi-story building in downtown Tel Aviv.

Just as important, however, were several factors that worked synergistically to reduce the vulnerability of the Israeli population. Warning information from U.S. satellites enabled people to be in their sealed-room shelters rather than out in the streets when the missiles fell. As the V-1 versus V-2 casualty data from London indicates, even very brief warning can reduce casualties by at least a factor of two. In addition, air attacks on Iraqi missile launchers forced the Iraqis to launch almost all of their attacks at night, when people would be at home and only needed to step into their shelters.

Given that most Israelis were in their sealed room shelters during the missile attacks, the quality of these shelters becomes a crucial factor. The typical Israeli apartment building is constructed of reinforced concrete, and is thus collapse-resistant. In contrast, in London the typical dwelling was a row house with load-bearing walls, which readily collapsed due to nearby explosions. In London reinforced buildings had demolition areas eight times smaller than buildings with load-bearing walls. This has important implications for casualties, because even if a building's walls were blown in, injuries to the inhabitants were generally minor as long as it did not collapse.

Taken together, these factors could account for the relatively low casualties due to the Scud attacks. However, in any attack involving relatively small numbers of inaccurate, conventionally-armed missiles, luck will also inevitably play a crucial role. Changing the impact point of a single warhead by a few tens of meters could have completely changed the nature of the casualties due to the Scud attacks.

Aside from defensive countermeasures such as the deployment of Patriot, provision of warning, and civil defense measures, the Coalition launched a vigorous offensive countermeasure campaign. Of the roughly 42,000 strike sorties flown by coalition aircraft during the war, about 2500 were against Scud-related targets, including about 450 against Scud production and support facilities, 750 against fixed launchers or possible hiding places for mobile launchers (such as buildings or road overpasses), and 1200 searching for mobile Scud launchers. In addition, special forces teams were placed into Iraq to assist in the search for mobile Scud launchers.

However, while most or all of the fixed Scud launchers were quickly destroyed, few if any of the mobile Scud launchers--which were the ones actually used to launch the missiles--were destroyed. However, the rate of the missile attacks did fall off sharply after the first week (and the accuracy of the missiles also appeared to decrease, at least in Israel) which was perhaps at least in part due to the Coalition air attacks.

The U.S. also used ground-attack missiles. Unlike the missiles discussed previously, these were highly accurate ballistic and cruise missiles used against point industrial and military targets. 282 Tomahawk conventionally-armed land-attack cruise missiles, with ranges greater than 1000 km, were used against targets such as nuclear and chemical weapon facilities, surface-to-air sites, and command and control facilities, including many targets in Baghdad. On the first night of the war, an additional 35 conventionally-armed air-launched cruise missiles were used against targets such as communication facilities and electrical power sites in northern Iraq. These missiles, which were delivered by B-52s flying from the continental U.S., used information from Global Positioning System satellites for terminal guidance. The U.S. Army also fired about 20 to 30 Army Tactical Missile Systems ballistic missiles. These 100-km range missiles were used against targets such as surface-to-air missile sites, logistics sites, and howitzer and rocket batteries. These US missile attacks were generally successful.


Ballistic (and cruise) missiles have been used for a variety of reasons: when bombers were not a viable option, to avoid risking pilots and airplanes, for psychological effects, or to retaliate or deter. In only one case do missile attacks appear to have possibly significantly affected the course of a war: the Iraqi missile attacks during the War of the Cities may have contributed to the Iranian decision to end the Iran-Iraq war. In the majority of the cases (Germany, Afghanistan, Iran, Iraq in 1991), the missile attacks failed to achieve their objectives. The U.S. missile attacks during the Gulf War may have achieved many of their objectives, but given the Coalition's overwhelming air superiority, were not crucial to the war's outcome.

At present, there is no direct theater ballistic missile threat to U.S. territory. The threat to U.S. allies and forces deployed overseas is almost exclusively in the form of inaccurate, conventionally-armed (or possibly chemically-armed) missiles such as the Scud and its derivatives. Such missiles are too inaccurate to pose a serious military threat, and are primarily of concern as a terror threat against cities.

The casualties to be expected due to such terror attacks will be highly dependent on the circumstances of the attacks, and moreover large statistical fluctuations in casualties would be expected for small-scale attacks by inaccurate missiles. As the Iraqi Gulf War missile attacks demonstrate, warning and proper sheltering can reduce casualties. However, it should not be assumed that the relatively light casualties inflicted by the Iraqi Scuds necessarily will be the case for future attacks. Iraqi Scuds were very inaccurate and had small warheads; plausible increases in accuracy coupled with larger warheads could increase the expected lethality by a factor of 10.

If chemical warheads are used in terror attacks on cities, casualties will again be highly dependent on circumstances, in particular on how well the chemicals are dispensed, the weather, and how well the population is prepared. If the chemicals are efficiently dispersed, even a well prepared and equipped population in favorable weather conditions could suffer casualties several times higher than for a conventional attack. If the weather conditions are unfavorable (for example, a calm, clear night) casualties are likely to be much higher.

The threat from theater missiles will change dramatically if GPS-guided missiles (in the near-term, more likely cruise rather than ballistic missiles) begin to proliferate. Such missiles could be accurate enough to pose real military threats in addition to being even more destructive as terror weapons. Missiles armed with nuclear (or possibly biological) warheads would of course represent an even greater threat.

Relatively straightforward defensive countermeasures, such as providing warning and shelters, or in the case of chemicals, adequate gas masks and training, can significantly reduce casualties from missile attacks. On the other hand, more expensive and technically-complex approaches, such as terminal defenses or attacks on missile launchers, have so far had relatively little success. The Patriot experience in the Gulf War highlighted the fundamental problem facing active missile defenses: how to deal with the countermeasures employed by an attacker. At present it is unclear what level of effectiveness missile defense systems can expect to achieve in the face of countermeasures.

The author is with the Defense and Arms Control Studies Program at M.I.T.

Symposium on Theater Ballistic Missiles: What Is the Threat? What Can Be Done?

Physics and Society presents here papers based on four of the five talks given at the invited session on Theater Ballistic Missiles, held at the APS meeting in Washington, DC, on 18 April 1994. Lisbeth Gronlund presided over the session. The fifth paper, "Arms Control Options for Ballistic Missiles" by Lora Lumpe, could not be published in this issue due to space limitations; it will be published in the next (January 1995) issue.

The Theater Ballistic Missile Threat in Context

Gerald L. Epstein When potentially armed with weapons of mass destruction--defined here to be nuclear, biological, and chemical weapons--theater ballistic missiles acquire far greater significance than they would have if restricted to conventional warheads. When conventionally armed, theater ballistic missiles are too inaccurate to pose any significant threat to military targets. Even so they can have enormous political significance, as shown by the Iraqi Scud missile attacks during the Gulf War. The indirect military significance of these attacks was also substantial, given the diversion of coalition air power to the hunt for these missiles on the ground. Similarly, the deaths of 11 American soldiers in Somalia in 1993 ended up reversing the course of U.S. military involvement, even though those losses did not constitute a military defeat. Nevertheless, it is weapons of mass destruction that make theater ballistic missiles so dangerous. Although advanced delivery systems (including cruise missiles and combat aircraft in addition to ballistic missiles) are not required to deliver weapons of mass destruction, they make it possible for a proliferant state to threaten more of its neighbors with greater damage than it could wreak without such delivery systems.

Proliferation of weapons of mass destruction and ballistic missiles

Figure 1 shows those countries widely reported to have or to be acquiring weapons of mass destruction. This chart was compiled by OTA from various unofficial published tabulations and does not represent an official United States government list of proliferant states. Indeed, Director of Central Intelligence R. James Woolsey has said that over 25 states "may have or may be developing" weapons of mass destruction and means to deliver them, indicating that this figure apparently underestimates the total.

Figure 1. States possessing weapons of mass destruction.

Countries which are shaded in Figure 1 have, or are developing, ballistic missiles with a range equal to or greater than that of a Scud missile. It is evident that states suspected of pursuing weapons of mass destruction also tend to seek missiles with which to deliver them. It should also be noted that all these countries, with the possible exception of Myanmar (Burma), have combat aircraft capable of delivering weapons of mass destruction.

Table 1, also drawn from unclassified sources, lists states in the developing world that are thought to be pursuing ballistic missiles. The underlined countries, corresponding to the shaded countries in figure 1, represent states pursuing both missiles and weapons of mass destruction. According to OTA, most of the countries in the top three tiers could advance upward in the list by about one category over the next decade, but whether they will or not depends on factors such as how committed they are to their missile programs and to what degree potential suppliers of missile technology are able to control relevant exports. In particular, OTA noted that "among the handful of countries with both the technological capability and the resources to develop long range ballistic missiles over the next decade, few if any would likely have the intent to target the United States."

Table 1: Ballistic missile powers in the developing world

Advanced	Able to design and produce missiles   India, Israel, possibly
	        comparable to those produced in the	Taiwan
		U.S. in the mid-1960s
Intermediate	Able to reverse-engineer, introduce 	N. & S. Korea, Brazil
		changes to, and manufacture Scud-like   and possibly Argentina
		missiles, and to make solid propellant  and South Africa
		short-range missiles
Incipient	Some capability to modify existing	 Egypt, Iran, pre-war 
		Scuds but little else			 Iraq , Pakistan
No Indigenous 	No missile design or manufacturing 	Anghanistan, Libya, 
Capability	capability, but have imported missiles 	Yemen, Saudi Arabia, 
		with ranges above 100 km.		Syria, possibly Algeria
							and Cuba

Source: Adapted from the OTA Assessment "Technologies Underlying Weapons of Mass Destruction," OTA-BP-ISC-115 (U.S. Government Printing Office, Washington, DC, December 1993), p. 212.

Choice of delivery system

The delivery systems pursued by a state will depend greatly on which systems are available to it. They will also depend upon the proliferant state's intended mission. Does it just want to be able to intimidate a neighbor, or to execute terror attacks against more distant civil targets? In either case, military delivery systems are unnecessary. Countering an overwhelming conventional attack on its own territory, or attacking a much more heavily armed foe, will require a more robust delivery capability. Perhaps the most important factor is whether a state needs to have demonstrated a delivery capability to itself and to others--in which case dedicated military systems such as ballistic or cruise missiles or combat aircraft may be necessary--or whether it needs merely to imply that it might have a means of delivery without actually demonstrating it.

Comparing aircraft to missiles

A state free to choose among delivery systems will evaluate delivery systems according to how well characteristics such as range, payload, accuracy, and flight time enable it to conduct its intended missions. The most important of these characteristics are range and payload. Typical range/payload combinations available to developing countries are shown in Figure 2. Although this figure presents a single range and payload for each system, in reality each should be represented by a curve; range can be extended at the expense of payload and vice versa. Moreover, particularly for combat aircraft, range depends on a host of parameters besides payload, such as the flight profile. Nevertheless, a few general conclusions can still be drawn from Figure 2. First of all, the range of all these systems is quite limited; none of the systems have ranges much over 1000 kilometers. Second, the aircraft shown here carry much greater payloads and typically travel further than the ballistic missiles. Cruise missiles, not shown, have smaller range and payloads than even the ballistic missiles; at present, only the U.S. and Russia have deployed cruise missiles with greater range/payload capability than an unmodified Scud missile.

Figure 2. Representative delivery systems.

Accuracy is not terribly important for delivering weapons of mass destruction; most of the missiles shown here have accuracies no better than about 1 km, but that would certainly be sufficient for conducting a nuclear attack. To the extent that accuracy matters, aircraft are considerably better than ballistic missiles. Taking advantage of satellite navigation systems, cruise missiles can be given accuracies on the order of 100 meters, far more precise than would usually be necessary to deliver weapons of mass destruction.

Ballistic missiles are far more effective than aircraft at penetrating defenses, as the Iraqi Scud attacks against Israeli, Saudi, and American air defenses made clear. The ability to penetrate even highly effective air defenses is most likely responsible for the demand for these missiles on the part of proliferant states. With their short flight times, missiles provide little warning of their arrival. Like ballistic missiles, cruise missiles could also be highly successful at evading detection and penetrating defenses, relying on low observability rather than on the high reentry velocities that make ballistic missiles so difficult to defend against. Aircraft take longer to arrive than ballistic missiles, but unlike missiles they may be able to evade detection until close to their target.

Delivery system cost is probably not very important to a state pursuing nuclear weapons, since nuclear weapons will cost far more than whatever system is chosen to deliver them. To the extent that cost matters, ballistic and cruise missiles are considerably cheaper than manned aircraft. On the other hand, aircraft already in a proliferant's arsenal may not represent an additional expense. Moreover, aircraft are reusable, although this fact is irrelevant when only a few weapons are to be delivered. Possibly more relevant than the relative cost of missiles and aircraft would be that missiles can be launched by small teams, whereas quite a large infrastructure is required to maintain and operate combat aircraft. Tighter operational control can therefore be exerted over missiles; and fewer people who might disobey orders or even misappropriate weapons are involved.

Controlling the spread of delivery systems

Table 1 shows that many states already have Scud-class missiles, having purchased or been given them during the Cold War. These missiles are being studied and, possibly, reverse-engineered. However, it is easier to redesign the Scud than it is to build a completely new design. In order to forestall the further proliferation of ballistic (or cruise) missiles and missile technology, seven Western industrialized nations formed the Missile Technology Control Regime (MTCR) in 1987. MTCR parties initially agreed not to export to non-parties ballistic or cruise missiles capable of delivering 500 kg to a distance of 300 km or more. In 1993, controls were tightened to cover missiles with 300 km range at any payload, or any missile at all that the seller had reason to believe would be destined to carry weapons of mass destruction. Components of and technology to produce such missiles are also covered. The MTCR forces states seeking to develop missiles to do so indigenously, or to purchase them from one of the few remaining suppliers that have remained outside the MTCR.

By the end of 1993, some thirty states had joined or agreed to abide with the MTCR constraints. However, North Korea's emergence as a missile exporter makes clear that the set of states capable of supplying missile technology now includes states seeking to acquire their own weapons of mass destruction and delivery systems. This situation makes it difficult to establish universal export control regimes: If such states are excluded from the regime, they are left free to undercut the export controls that MTCR members agree to impose; if they are invited to join, they will gain access to technologies that MTCR members share with each other but exclude from non-members.

Controlling the spread of combat aircraft is even more difficult. Whereas the creation and growth of the MTCR has had some success at delegitimizing the sale of longer-range ballistic and cruise missiles, combat aircraft are widely possessed by almost all countries of proliferation concern and are widely available on international markets. Moreover, in most cases the range, accuracy, and payload capacities of combat aircraft already possessed by developing countries far exceed those of their ballistic or cruise missiles, and many more countries have aircraft than missiles.

Although only 11 countries have designed and produced anti-ship cruise missiles (ASCMs) indigenously , such systems can readily be purchased and have spread to over 40 developing countries. In general, however, cruise missiles are easier to develop than ballistic missiles, at least for systems with range under a thousand kilometers. Indeed, low-technology systems such as modified civil airliners could be developed quite easily. Therefore, cruise missiles represent a potent threat for delivering weapons of mass destruction in the longer run.


This paper is largely based on chapter 5 of the Office of Technology Assessment study Technologies Underlying Weapons of Mass Destruction, OTA-BP-ISC-115 (Washington, DC: U.S. Government Printing Office, December 1993), and references cited there. However, the material presented here is the responsibility of the author, who directed that study, and does not represent the views of the Office of Technology Assessment, the U.S. Congress, or the Technology Assessment Board.

The author is with the Office of Technology Assessment, U.S. Congress.

Symposium on Theater Ballistic Missiles: What Is the Threat? What Can Be Done?

Physics and Society presents here papers based on four of the five talks given at the invited session on Theater Ballistic Missiles, held at the APS meeting in Washington, DC, on 18 April 1994. Lisbeth Gronlund presided over the session. The fifth paper, "Arms Control Options for Ballistic Missiles" by Lora Lumpe, could not be published in this issue due to space limitations; it will be published in the next (January 1995) issue.

The Defense Counterproliferation Initiative

Bill Heiser The concerns I am about to express are shared at the highest levels of our government. President Clinton has been concerned about weapons of mass destruction for some period of time, and in a speech to the UN General Assembly in September 1993, noted, "One of our most urgent priorities must be attacking the proliferation of weapons of mass destruction, whether they are nuclear, chemical, biological; and the ballistic missile that can rain them down on populations hundreds of miles away....If we do not stem the proliferation of the world's deadliest weapons, no democracy can feel secure." The ballistic missile is the delivery means that we are particularly concerned about. It seems to be the proliferant countries' choice for the delivery of weapons of mass destruction.

The proliferation scene is growing more chronic. More than 25 countries may have or are developing nuclear, biological, and chemical weapons, and the means to deliver them. More than 12 countries have operational missiles and more have development programs. The trend suggests that we are going to be confronting more accurate, more lethal systems in the future. The demise of the Soviet Union offers potential sources of technology and know-how to actors trying to profit from post-cold war regional instabilities. The Congressional Office of Technology Assessment (OTA) has done a lot of good work pointing out how greater commercial availability of dual-use technologies is going to put into the hands of more and more proliferants the kinds of enabling technologies to make this threat more frightening over time.

I would like to talk briefly about the lessons learned from Desert Storm. We were very fortunate in Desert Storm. We discovered that there was a nuclear program in place far beyond what we had anticipated. It is very difficult to discern these kinds of activities in countries like Iraq. We also found that we need to improve our understanding of the collateral consequences of attacking nuclear, biological, or chemical facilities. As you can imagine, one would want to think very carefully before employing any kind of device--even a conventional precision-guided weapon--against a nuclear, chemical, or biological facility.

We were fortunate in Iraq because there were no contamination problems. Why wasn't Iraq's large chemical arsenal used? You heard in an earlier presentation that chemical weapons were found after the war ended. Why weren't they used? To be honest, we are not sure. One would assume that the leadership thought the risks would be unacceptable if they attempted to employ those munitions.

We have alluded to the military ineffectiveness of Ieaq's Scuds, but I think you will all recall the impact that this inaccurate weapon system had. It was conventionally-armed during that conflict, but as was pointed out in the previous presentation, when even these inaccurate systems are equipped with nuclear, chemical, or biological warheads we are talking about a dramatically different kind of threat.

The legacy we intend to leave behind in the Department of Defense (DOD) is that we improved the ability of our armed forces to deal with this kind of threat in the future. In this way we won't have to rely on luck to carry us through the day.

Why are weapons of mass destruction of such concern? Over time we have been placing less reliance on US nuclear weapons. Consequently, our strategy in responding to allies' security concerns has been to bring tremendous amounts of conventional forces to bear on specific trouble spots in a very short period of time. A problem arises if a proliferant country has weapons of mass destruction in its arsenal--it can disrupt and delay that strategy. Conventional commanders on the ground, our armed forces, and our allies' armed forces will not be able to rely on the rapid deployment and introduction of ground forces, because they will have to be concerned about the weapons of mass destruction that the opposing parties could deploy. Because commanders would have to assume that their forces could be threatened, they would have to operate in what we would call a nuclear-safe--or chemically or biologically-safe--environment that slows down the military effectiveness of our forces and consequently creates a situation where we cannot be confident of the outcome.

The Defense Counterproliferation Initiative tries to reverse this situation by ensuring that we can prevail even when facing aggressor forces equipped with weapons of mass destruction. The Secretary of Defense is responsible for ensuring that US forces have the wherewithal to deal effectively with this threat, which is here and now.

A good short hand for understanding counterproliferation is that it equals prevention plus protection. The DOD supports the activities of the State Department and other agencies to prevent the acquisition or the development of weapons of mass destruction. Prevention remains our preeminent goal. We don't wish to reach the state where we have to engage our armed forces. But at the same time we know that prevention is not going to be successful in all cases. North Korea, for example, is a proliferation nightmare today. So we have to look at proliferation not only as a diplomatic problem, but as a military threat, one that our armed forces must be prepared to deal with. Thus, the counterproliferation program includes proliferation prevention, and the military preparations required to address this very real security threat.

Let me give you some examples of non-military prevention activities. We are currently supporting the UN in Iraq by providing assistance in broad-area surveillance and technical expertise on the detection of chemical weapons and ballistic missiles that is needed in inspections of various sites. We analyze samples in support of the International Atomic Energy Agency, and help train inspectors to verify the Chemical Weapons Convention. We also have an office that reviews export licenses to ensure that we ourselves don't contribute to the proliferation of weapons of mass destruction by third parties or developing countries. In terms of export controls, we deal with what we call "choke points" or precursors to certain technologies. Preventing developing countries from developing these sensitive technologies will protect our security interests and those of our allies.

The other aspect is protection. We in counterproliferation policy work closely with our colleagues in acquisition and in strategy and doctrine. We also work with people in the intelligence community, and pursue international cooperation with our allies to deal with the threat posed by weapons of mass destruction. We need to develop a range of military capabilities to ensure that weapons of mass destruction are not used by potential proliferants.

Let's talk for a moment about the relationship between counterproliferation and missile defense. As I mentioned earlier ballistic missiles seem to be the delivery means of choice for chemical, biological, or nuclear weapons. We have re-oriented our ballistic missile defense program to focus on the theater missile threat. We have to be prepared to deal with nuclear payloads, and canisterized chemical weapons and biological weapons. For this reason, our program in ballistic missile defense is focused, more than ever before, on boost or ascent phase intercept. We are reaching the stage where we can't permit a proliferant country to succeed in launching nuclear, chemical or biological weapons outside their own airspace. During Desert Storm, I believe in at least one incident, a Patriot struck a Scud conventional warhead and deflected it. When the warhead landed, there were casualties. We can't permit that kind of situation to occur when dealing with weapons of mass destruction. Thus, the key to success is to ensure that missiles are destroyed upon launch. We continue to have serious problems in locating mobile missile launchers. In Desert Storm our success rate was negligible in tracking and destroying the mobile Scud launchers before they launched their conventional munitions.

What military capabilities will we need to implement our counterproliferation strategy? The US must be able to protect military forces, logistics facilities, civilian populations and national infrastructure. The US must defend against ballistic missiles from the Scud to the CSS-2, and more modern missiles in the future, armed with nuclear or chemical or biological warheads, and it must also defend against cruise missiles and unmanned air vehicles. While I've highlighted the ballistic missile threat in this talk, I was pleased to hear that OTA has also been focusing on cruise missiles. It is clear that the cruise missile poses a difficult threat. In fact, we anticipate that over time the cruise missile itself may become the delivery means of choice rather than the ballistic missile. Finally, some of the characteristics that an effective missile defense system should possess: low leakage, high lethality, multiple shot engagement capability, wide geographic coverage, and rapid deployment capability.

As I mentioned, the cruise missile threat is a compelling one. What we are likely to see is that the proliferant will find it easier, quicker, and cheaper to acquire and develop cruise missiles than ballistic missiles. Thus, I want to make it clear that we are not suggesting ballistic missile defenses should be enhanced at the expense of cruise missile defenses. In fact, we are finding in DOD that we are underfunding cruise missile defenses, and are going to begin shifting some funds accordingly.

I would like to talk about missile defense in the post-cold war era. Now I am not a physicist, or an expert on missiles. The experts customarily evaluate missile defense systems in terms of the ground area it can protect from an incoming missile--the so called "footprint." But when missiles are carrying nuclear, biological, or chemical warheads, it becomes essential to intercept the missile during the boost or ascent phase. It seems to me that it may be time for us to shift the thinking, the technical thinking, to place more emphasis on trying to put a shield or a cap over the territory of the nations of proliferation concern rather than attempting to protect the world. It might be more prudent to think in terms of putting a cap over Iraq, Iran, North Korea and other countries of concern so that we can guarantee that they could not launch outside of their air space.

One of our precepts is that we should draw as much as possible on existing capabilities. We should take existing forces and incrementally improve them to deal with the weapons of mass destruction threat that I just described to you. So don't think that we are about to unfold a billion-dollar program to deal with this threat. We are going to take the existing force structure and try to make incremental adjustments to deal with the proliferation threat.

The last point I want to make is that in order to deal with missile defense over time we cannot afford to close off the technological avenues needed to handle an ever-increasing threat--both in terms of cruise missiles and ballistic missiles. Therefore I want to raise some Anti Ballistic Missile (ABM) Treaty considerations. You may recall that in previous administrations there was quite a dispute over whether we were going to use a narrow or broad interpretation of the ABM Treaty. That is no longer an issue in this administration. What we do believe is important is to ensure that the treaty allows us to deal with the new circumstances. It has got to have enough resilience to allow us to deal with this emerging threat. Therefore, it is time to clarify some of the treaty provisions to allow us to make the adjustments that are going to be needed. That is not to say that we wish to make the ABM Treaty ineffective. But to deal with the threat I have described to you, we are going to have to make some changes to the Treaty. We need to preserve our option to respond to these emerging threats with what we are calling a "modernized ABM Treaty." We shouldn't put ourselves into a situation of forcing a choice between the legitimate security needs of the United States and its allies and maintaining an ABM Treaty that is inflexible.

The author is Director for Military Assessment and Response, Office of Counterproliferation Policy, Office of Assistant Secretary of Defense for Nuclear Security and Counterproliferation, U. S. Department of Defense.

Symposium on Theater Ballistic Missiles: What Is the Threat? What Can Be Done?

Physics and Society presents here papers based on four of the five talks given at the invited session on Theater Ballistic Missiles, held at the APS meeting in Washington, DC, on 18 April 1994. Lisbeth Gronlund presided over the session. The fifth paper, "Arms Control Options for Ballistic Missiles" by Lora Lumpe, could not be published in this issue due to space limitations; it will be published in the next (January 1995) issue.

The Conflict Between Highly Capable Theater Missile Defenses and the ABM Treaty

David Wright The debate over missile defenses has changed over the past few years, with the development of theater missile defenses (TMD) being given a much higher priority and budget than in the past. This process was accelerated by the 1991 Persian Gulf War, which raised concerns in the U.S. about theater ballistic missiles.

As discussed below, the Clinton administration is now attempting to modify the Anti-Ballistic Missile (ABM) Treaty to allow the development and deployment of highly capable TMD systems. Although the administration claims that its proposed treaty changes are only "clarifications" of the treaty, an analysis shows they would effectively undermine the treaty, with potentially significant implications for international security. The proposed changes have not received the attention they deserve given the importance of the treaty and the potential impact of the changes.

Planned TMD systems and ABM compliance issues

The U.S. is planning the development of several advanced TMD systems, the first of which--the Theater High Altitude Area Defense (THAAD) system--is scheduled to begin initial flight testing early in 1995. THAAD is intended to intercept theater missiles of ranges up to 3500 kilometers, with intercepts occurring at long distances (several hundred kilometers) and high altitudes (above 100 kilometers) in order to defend large ground areas (hundreds of kilometers across).

The cost of THAAD is estimated at $10 billion, not including operation and maintenance costs, with deployment to begin in 2001. Current plans call for more than 1300 interceptors. Since TMD systems are intended to be mobile, THAAD is designed to be transportable by aircraft. Beyond THAAD, the Navy is planning an even more capable TMD system that would be ship-based, and the Air Force is considering an air-launched system intended to intercept missiles during their boost phase.

It is generally agreed that THAAD and the more capable TMD systems being considered would be sufficiently capable that they would violate the ABM Treaty in its current form. As a result, the U.S. has proposed to Russia changes to the treaty that would allow these systems.

The ABM Treaty, signed by the U.S. and the Soviet Union in 1972, is widely viewed as an important foundation of strategic nuclear arms control. By restricting the development and deployment of strategic ballistic missile defenses, the treaty removed an incentive for strategic offensive arms build-ups and made possible the reductions of strategic forces negotiated in the START and START II agreements.

The ABM Treaty limits TMD systems in two ways. First, it prohibits giving them a "capability" to counter strategic missiles, regardless of whether this capability is tested. Second, it prohibits testing TMD components or systems in an "ABM mode"--that is, testing them against targets with the characteristics of strategic missiles--regardless of whether or not the system is capable of intercepting a strategic target.

Thus TMD systems can be freely developed and deployed as long as they are neither capable of countering strategic targets and are not tested against strategic targets. In particular, the treaty provisions ban overdesigning TMD systems to give them strategic capabilities, since as soon as a TMD system, or one of its components, is given a capability to counter strategic missiles, it becomes subject to the treaty's limitations on ABM systems, even if it has never been tested in an ABM role.

Since the ABM Treaty neither defines the difference between theater and strategic missiles nor provides a definition of what it means to have a capability to counter strategic missiles, there is some uncertainty in drawing a line between strategic and theater defenses, and the U.S. and the Soviet Union have never reached a common understanding on how to do so. In the past, the U.S. has used the internal criterion that any test against a target moving faster than 2 km/s or at an altitude greater than 40 kilometers must undergo a treaty compliance review. Although this criterion has never been made official U.S. policy, it was the understanding when the Senate ratified the treaty. This criteria was intended to be stringent to ensure there was no ambiguity about the potential ABM capability of TMD systems, since limiting ABM capability is the point of the ABM Treaty.

Is the ABM Treaty still important?

The ABM Treaty remains important for several reasons. While a renewed U.S.-Russian arms race seems unlikely, limits on ABM systems are important for preserving the option of future deep cuts in nuclear arsenals. The deployment of defenses with ABM capability would effectively place a lower limit on the size of arsenals the U.S. and Russia would want to retain. Since the existing Russian nuclear arsenal remains the greatest security threat to the U.S., preserving the possibility of deep reductions is important. John Holum, director of the U.S. Arms Control and Disarmament Agency (ACDA), testified to Congress that the ABM Treaty "is indispensable to stability, to START I and START II reductions, and to longer term strategic reduction opportunities."

Weakening the ABM Treaty could affect the smaller nuclear powers in ways that could hinder nonproliferation efforts. France, Britain, and China's nuclear arsenals are small compared to the numbers of THAAD interceptors being planned. Weakening the treaty could cause these countries to consider building up their arsenals--especially China, which is believed to have fewer than 20 strategic missiles. A Chinese buildup could cause serious concern and possibly reactive buildups in India and then in Pakistan.

But even short of actually building new weapons, to preserve its option of making more bomb material in the future, these countries would very likely refuse to participate in a ban on the production of fissile material for weapons--an initiative that President Clinton announced as the centerpiece of his non-proliferation efforts last fall. Britain and France would likely refuse to join such a ban. Moreover, China might refuse to join a Comprehensive Test Ban in order to preserve its option of developing MIRVed warheads to counter defenses.

Because military planners make worse-case analyses, even if future missile defenses would not work well enough to actually protect against missile attacks, their existence would likely be enough to scuttle future arms control measures. Making sure the uncertainties that lead to worse-case analyses do not interfere with arms control was the whole reason behind the ABM Treaty, and it has not gone away.

The U.S. proposal to change the treaty

To proceed with the testing and deployment of THAAD and other TMD systems, the administration has proposed to Russia that the ABM Treaty be modified to define a dividing line between theater and strategic missile defenses in a way that would permit the development, testing and deployment of THAAD and considerably more capable missile defenses. The crucial issue is whether such a definition would continue to prevent the deployment of TMD systems with significant ABM capability.

Under the proposed changes, a missile defense would not be considered to be a strategic defense unless it was tested against a target with a speed greater than 5 km/s. Moreover, the treaty's prohibition against giving non-strategic defenses a "capability" against strategic missiles would be eliminated. Thus if the U.S. proposal is put into effect, any system that has not been tested against a target having a reentry speed greater than 5 km/s would be considered to be a TMD system, and thus not limited by the ABM Treaty, regardless of its actual capability to counter strategic missiles.

Since the administration's stated goal is to continue to limit the ABM capability of TMD systems, and since this restriction on the target speed is the only restriction it is proposing to Russia, the administration's position must be that target speed is the crucial parameter in determining the ABM capability of defensive systems. Since ICBMs reenter the atmosphere at about 7 km/s, the administration must argue that the 40% difference in target speeds between 5 and 7 km/s is large enough to provide a clear buffer or "firebreak" between theater and strategic defenses, i.e., that if a missile defense was highly capable against a 5 km/s target, it would nonetheless have negligible capability against a 7 km/s target.

Possible strategic capabilities of TMD systems under the U.S. proposal

Despite its claim that TMD systems limited to tests against 5 km/s targets would not have a significant capability against strategic missiles, the Administration has not published any analysis to support this claim. In fact, the only detailed, publicly available analysis shows that if TMD systems capable of countering 5 km/s reentry vehicles can be built, these systems would have significant capabilities against strategic targets as well. As a result, the U.S. proposed treaty changes would undermine the fundamental objective of the ABM Treaty.

The analysis mentioned above calculates the ground area, or "footprint," that could be defended by a defense system similar to THAAD. The footprint size depends on a number of factors, including the target speed, but also the speed of the interceptor missile, and the range at which the TMD-radar can detect the incoming missiles, since the interceptor is assumed to be launched only after the radar detects the target. The detection range is especially important and depends on the capability of the radar, the radar cross-section of the target, and the amount of information on the target's position that is available from other sensors, since such "cueing" can significantly reduce the area of sky that the TMD-radar must search to find the target.

To understand the importance of target speed on the performance of a defense system, the analysis considered a range of values for parameters such as the radar cross-section of the target, the power-aperture product of the radar, the amount of cueing available, and the interceptor speed. For each case, the footprint of the TMD system was calculated against both 3000 and 10,000 kilometer-range missiles, which correspond roughly to target speeds of 5 and 7 km/s.

Figure 1 shows footprints from this analysis assuming a THAAD-like TMD system for a case of minimal cueing--the only information provided is the launch site of the attacking missile. Although the footprint against the 10,000 km range strategic missile (dashed line) is somewhat smaller that the footprint against the 3000 km range theater missile (solid line), they are roughly comparable in size, and both are much larger than a large city or a missile deployment area.

If additional cueing is available, the footprint can grow significantly. With cueing provided by early warning radars similar to those used by the U.S. and Russia, the strategic footprint in Figure 1 would grow to roughly 700 km across and 1200 km front to back for the same defense system. Such cueing is not forbidden by the ABM Treaty.

Thus the analysis shows that if a TMD system is capable of defending a substantial area against a theater missile attack, it will also be capable of defending a somewhat smaller, but still significantly large, area against a strategic attack, even if it was not designed specifically to counter strategic missiles. This relationship holds true over the wide range of parameters values considered in the study.

Figure 1. The defended areas calculated for a THAAD-like TMD system against a 3,000 km-range theater missile (solid line) and a 10,000 km-range strategic missile (dashed line), assuming a TMD-radar power-aperture product of 500,000 W-m2, target radar cross-section of 0.005 m^2, maximum interceptor speed of 2.6 km/s, and minimal cueing.

For the THAAD interceptor, which has maximum speed of about 2.6 km/sec, the difference in reentry speeds of a theater and strategic target translates into roughly a 25% difference in closing speed. If uncompensated for, this difference in closing speeds could lead to a somewhat lower single-shot kill probability against the strategic target. However, unless the capability of the interceptor against the theater target was marginal to begin with, the kill probability would be expected to degrade gradually as the target speed increases, and a 25% difference in closing speed is small enough that the interceptor would be expected to retain a significant kill probability against a strategic target. In addition, under the Administration's proposal it would be legal to overdesign the interceptor so that it would be expected to retain its full capability at full strategic closing speeds. Moreover, in the absence of limits on the closing speeds in tests (or an equivalent limit on the maximum interceptor speed), an exoatmospheric interceptor could in fact be tested at full strategic closing speeds simply by boosting the interceptor to a higher speed.

The ABM Treaty in its present form would ban the testing or deployment of such a THAAD-like system on the grounds that it is a non-ABM system with capabilities to counter strategic missiles. But under the administration's proposal, deployment of such a system would be allowed as long as the system is not tested against a strategic missile. Although the administration argues that the ban on testing against a more than 5 km/sec target would limit the strategic capabilities of a theater defense, in fact it is not a serious obstacle to giving a TMD system such capabilities.

Proponents of the administration's proposal argue that no military planner would rely on a TMD system to counter strategic missiles if the system has not been tested against a strategic missile. However, the experience of the 1991 Gulf War shows that this is not correct. The Patriot missile system was used against 600-km-range Iraqi Al-Hussein missiles despite the fact that Patriot had only been tested against missiles with half this range. Patriot was used because it was the only system available. If, in the future, there appears to be a real danger of strategic missile attack on the U.S. or Russia, and TMD systems exist that might be able to provide some degree of protection for major cities, then it is quite likely, that these TMD systems would be used for this purpose. In planning their future nuclear forces, the U.S. and Russia would certainly factor in the possibility that TMD systems would be used in this way. This is exactly the situation the ABM Treaty intended to prevent.


The administration is incorrect in its claim that its proposed changes will preserve the ABM Treaty. In particular, it shows that if a missile defense is assumed to be able to defend a large ground area against a 5 km/s target, then other things being equal it will also be able to defend a large ground area against a 7 km/s target.

The author is with the Union of Concerned Scientists and Defense and Arms Control Studies Program, MIT.