The United States currently has roughly a thousand strategic launchers with several thousand warheads, a number expected to drop to roughly two thousand under the Moscow Treaty. These strategic nuclear warheads have yields ranging from 100 to 500 kilotons and are the core of the US strategic deterrent. Such strategic deterrence seeks to convince adversaries that the benefits of hostile actions would be far outweighed by the consequences. Although the Soviet threat which they were developed to address has all but disappeared, emerging nuclear threats from proliferation and terrorism reinforce the need for deterrence.

These strategic nuclear weapons have formidable destructive power -- the smallest being some seven times more powerful than the bomb dropped on Hiroshima. This paper will examine what targets such weapons could be used against in regard to potential US nuclear adversaries.

At the low end of the spectrum, terrorist groups form a new potential nuclear adversary. They pose a unique problem because they are not susceptible to deterrence. One reason for this is the lack of any return address -- no clear target to retaliate against. Nuclear forensics might eventually pinpoint the source of nuclear materials involved, but even that would not show any intent on the part of the originator. It's even possible that material used would have been somehow pilfered from US stocks. Retaliatory strikes against potential supplier countries are discussed below.

There is another nuclear threat that deterrence is totally useless against. That is the threat of some kind of rogue commander or insider launching an attack or supplying weapons or materials to an outsider. To guard against such an eventuality, US nuclear forces employ a wide range of physical controls as well as an intensive personnel screening program. We have presumably supplied some of these systems to our British and French allies. The Russians certainly have their own systems; as part of our Nuclear Threat Reduction Initiative we have presumably encouraged them to improve on whatever systems they had and perhaps even given them some support. There is little information, certainly publicly, about Chinese, Indian and Pakistani protection systems. We assume all these systems work, but even in the US case there is cause for concern:

- In one well known incident in 2007, six armed nuclear cruise missiles were accidentally flown from North Dakota to Louisiana and then left outside unattended for hours. No one noticed. The problems directly associated with this incident were assuredly corrected. But the problem which cannot be corrected is that these systems are designed and run by humans, and humans make mistakes. And if incidents can happen accidentally, they are certainly even more likely if an insider is trying to make them happen.

- A major diamond heist in 2003 had some chilling lessons. In this case, one of the most highly guarded civilian facilities in the world, a diamond vault in Antwerp, was broken into by a gang of thieves. The thieves surveyed a wide range of protection systems and very creatively and cleverly designed a way to systematically disable them all without anyone suspecting anything until the vault was discovered open and ransacked. This was done without any inside help.

- Cyber attacks are rated by the FBI as a threat second only to nuclear war and weapons of mass destruction. Unfortunately, computers are also an essential element in nuclear security and we hear daily of clever intrusions into protected systems. Those intrusions are the ones we hear about; discovered intrusions into our most sensitive systems would certainly be kept from the public domain if at all possible. And most of the ones we hear about are by outsiders. Computerized security systems are inherently vulnerable to creative, sophisticated approaches, all the more so if an insider is involved.

- There are numerous cases where highly trusted individuals -- Robert Hanssen and Aldrich Ames come to mind - turned against their agencies because of greed, sex, anger or ideology. The United States has an extensive Personnel Reliability Program, but the standards in other countries are unclear. These systems are also designed and run by humans; eventual failures are inevitable.

No amount of targeting can protect against this insider threat. And, in fact, the more targeting, the worse the insider threat because this means more systems, larger facilities, more people. And depending on the circumstances, an insider action could be mistakenly evaluated as an intended action, sparking a nuclear conflict.

Pakistan is one possible nuclear adversary. It is now an ally, but an unstable one with radical Islamic groups potentially able to take over all or part of the country. It has nuclear weapons and missles presumably able to carry them. And it could possibly supply terrorist groups and invite retaliation. Military strikes might also be considered to thwart radical takeover of nuclear facilities, or some subsequent expansion of nuclear capabilities. Strikes against cities would seem to be out of the question, even for retaliation. Hardened command facilities might make attractive nuclear targets, but these inherently require ground bursts. Carried out with a strategic weapon, such a strike would release large amounts of fallout; weather patterns could then contaminate any of the neighboring countries, including India, China, Russia, Afghanistan or Iran. Underground facilities are also notoriously difficult to pinpoint, so even strategic weapons could prove inadequate. Strikes against other military targets or major infrastructure facilities might also invite a nuclear option, but few of them would be appropriate for strategic weapons. And of course, any strikes against Muslim Pakistan, even retaliatory ones, would enrage radical Islamists everywhere and doubtless distress the entire world community. Pakistan might not be able in turn to retaliate directly, but it could certainly assist radical groups anywhere. Overall, nuclear strikes on an adversarial Pakistan are not very attractive and at most would require a handful of strategic weapons.

Iran poses a complex challenge. It is a US adversary and seems intent on acquiring a nuclear weapon capability. Although it does not pose a direct threat to the Untied States, it has spoken menacingly of Israel and has supplied Hamas, Hezbollah, and Iraqi insurgents with a wide variety of conventional weapons. Military actions could be envisioned to preempt the achievement of Iranian nuclear weapons capabilities. As in the case of Pakistan, fallout and targeting challenges make the use of strategic nuclear weapons against underground or hardened complexes unattractive and the political consequences of using nuclear weapons against a Muslim country make any such use even more unattractive. And even if such an approach were taken, there is a very low requirement for strategic nuclear weapons.

Iran also raises the touchy issue of extended deterrence -- US pledges to a nonnuclear country to respond to nuclear strikes against that country. But Iran's most likely target is Israel, which is not a nonnuclear country and has no recognized US "nuclear umbrella." While Iranian strikes on other friendly countries (e.g., Egypt) would certainly be possible, many of these states, although nonnuclear, also do not have any guarantees of a US "nuclear umbrella." Attacks against nonnuclear NATO allies (e.g., Italy) would also be possible and might call for a US response. But Iran has made no threatening gestures towards any of these other states and, even in such an extreme case, retaliation could not involve more than a few strategic nuclear weapons.

North Korea is a nuclear adversary; indeed, it's easy to argue that North Korea developed nuclear weapons precisely to deter US military action against it. And it works, probably being the prime global example of working nuclear deterrence. And if US strikes on underground facilities would be unattractive in Pakistan or Iran, they are even less attractive in North Korea which has a reputation of being a nation of moles, as well as highly secretive. In addition, North Korea holds South Korea, and to a lesser extent Japan, hostage. Even with conventional weapons it could severely damage Seoul from its present positions. Additional, any damage from nuclear strikes in North Korea would eventually have to be cleaned up by South Korea, while Japan, South Korea, China and Russia could all be subject to significant problems with nuclear fallout. And once more, there is a dearth of military or infrastructure targets appropriate for strategic nuclear weapons. Another US nuclear bombing of an Asian nation would certainly be very distressing to the global community. Nevertheless, both South Korea and Japan do enjoy a US "nuclear umbrella." They are both vulnerable to North Korean nuclear strikes, while it seems that the direct threat to the United States, even Hawaii or the Pacific Coast, is still minimal given the demonstrated poor performance of both North Korean nuclear weapons and missiles. Finally, North Korea poses another unique challenge since it is not only unstable, but fragile with senior leadership tightly concentrated. Were this leadership to sense an imminent collapse, it could potentially launch nuclear strikes in a final gesture of defiance. No amount of US military might could deter such a gesture. Overall, North Korea poses a particularly difficult nuclear challenge, but one in which strategic nuclear weapons have at most a minor role to play.

China is neither ally nor adversary, but something in between. It is a nuclear power with a relatively modest arsenal of perhaps a couple hundred nuclear warheads, though some estimates do run over two thousand, together with some fifty missiles capable of reaching the United States. In recent years it has greatly expanded its commercial ties with the United States, but it has also been engaged in a significant modernization of its military forces. There is a long-standing potential flash point with Taiwan, which China adamantly claims as part of China and the United States adamantly helps protect from Chinese military actions. China's conventional military improvements in this area are particularly troublesome, since they could overwhelm the combined US and Taiwanese conventional defense forces. This is becoming another instance in which nuclear deterrence actually works, as the relatively small Chinese nuclear capability certainly makes any US nuclear options in the area decidedly unattractive. A strategic nuclear exchange with China would be heavily unbalanced in the US favor -- China would suffer significantly more casualties than the Untied States. But the United States could expect, at a minimum, to lose several major cities. Coming out ahead would hardly make us winners; indeed, it would destroy our preeminent position in the world. Escalation to this level is obviously unattractive. Nuclear operations at lower levels (e.g., the destruction of US naval forces or Chinese military facilities) might invite some US use of strategic nuclear weapons. But the dangers of escalation make the use of even a few a high risk operation. China has also repeatedly vowed not to use nuclear weapons first. With its intercontinental arsenal far smaller than the US arsenal and with minimal counterforce capability, China poses little direct military threat to the United States. Instead, it is Chinese nuclear forces which deter a US nuclear strike more than vice versa. The Taiwanese challenge may also be slowly resolving itself, as China and Taiwan develop direct commercial and cultural ties. Overall, there is a potential use for only a few, if any, US strategic nuclear weapons against China short of a major exchange. US strategic nuclear forces undoubtedly have a significant counterforce capability against Chinese nuclear forces, but this would be sure to initiate a major nuclear exchange. Since China lacks any real counterforce or anti-ballistic missile capabilities, the only solid US requirement for strategic nuclear forces vis-a-vis China is for enough forces to mount a devastating retaliatory strike should China for some unlikely reason initiate nuclear strikes against the United States. Even this extreme case would require perhaps dozens, certainly not hundreds or thousands of US warheads, and few high-yield weapons.

That brings us to Russia, our former main adversary, now a competitive partner and still a potential future adversary, particularly as relations have gradually soured in recent years. Russia is the only other nation with a formidable arsenal of some three thousand strategic weapons. Our opposing arsenals were built up in the period when Mutually Assured Destruction (MAD) was the underlying strategic concept -- each side deterred from striking the other by the prospect of assured retaliatory destruction. The situation became even madder as both sides worked to develop a capability to destroy the other's strike force with a crippling first strike. This resulted in further large increases in the sizes of the arsenals, as well as early warning systems and hair-trigger launch-on-warning alert procedures. The final result was an overall system in which each side could destroy the other in a matter of minutes. And it also raised another chilling specter, Nuclear Winter, in which the atmospheric dust raised from a major nuclear exchange would block sunlight for an extended period and essentially destroy human civilization globally.

The collapse of the Soviet Union collapsed this threat, but did not eliminate it. US and Russian nuclear forces remained frozen in adversarial positions. The May 2002 Moscow Treaty began to address this legacy and is leading to a reduction in strategic nuclear forces down to levels of about two thousand on each side by 2012. These levels are still sufficient to destroy not only both nations but also human civilization. It is hard to even construct scenarios where the use of even a few strategic nuclear weapons does not risk a total escalation. Strikes on Russian warning facilities or strike forces would almost certainly bring a wave of retaliatory strikes. Strikes on hardened command centers would be of questionable effectiveness and also risk total escalation. In addition, successful elimination of Russian leaders could greatly complicate any efforts to stop escalation short of a total nuclear exchange.

Counterforce targeting requires a larger number of accurate, high yield weapons. And if some extreme circumstances actually pushed the United States to initiate such a strike, the outcome would probably be the mutual destruction we are both trying to avoid. Counterforce strike capabilities are typically considered part of the US deterrent, but it is unclear just what they are supposed to be deterring. They can't deter a Russian first strike since by definition once a first strike is launched, strategic delivery vehicles are already on the way and no longer subject to attack. In actuality, counterforce targets are not a deterrent, but a provocation. They clearly demand a logical Russian response of both increasing the number and capabilities of Russian strategic nuclear forces and also increasing their alert status to facilitate launch in the event a US first strike is detected. Neither of these actions is in the US interest. Eliminating counterforce missions would not reduce deterrence since such capabilities do nothing to prevent a Russian strike. And in a condition of high tension, when a US first strike might seem most attractive, Russian forces would almost certainly be in a launch-on-warning status. The core of deterrence remains Mutually Assurred Destruction and this requires neither high accuracy nor high yield weapons.

One recent analysis assessed the potential for replacing counterforce targeting with infrastructure targeting, proposing that such targeting could provide a strong enough disincentive to make a Russian strike on the United States unattractive. This would make a relatively small number of strategic nuclear weapons -- perhaps 500 -- adequate to deter a Russian strike.
US retaliatory forces are targeted, so far as we know, on Russian high-value targets (presumably major cities). These are also the targets which infrastructure targeting would replace, though it is not clear that threats to infrastructure carry as strong a deterrent message as threats to cities. But in either case, high-yield weapons are unnecessary. And there is a particular problem associated with using high-yield, high-accuracy delivery systems for retaliatory targeting. From the US point of view, these are retaliatory (i.e., deterrent) systems. From the Russian point of view, whatever their present targeting, they could be rapidly re-targeted to first strike (i.e., provocative) targets.

In summary:

• It is difficult to define rational targets for more than a small number (dozen?) strategic nuclear weapons. Our strategic nuclear forces are simply not configured for the contemporary threats which face the nation.
• In regards to Russia, the MAD legacy weighs heavily on both nations. A critical element is the counterforce weapons which constitute not a deterrent but rather a provocative asset.
• Eliminating the counterforce mission would improve national security by reducing the potential for accidental nuclear confrontations and by encouraging Russia (and China) to reduce their own nuclear forces.
• Reductions in strategic nuclear forces would release resources for other, more pressing applications.
• The more strategic nuclear targets there are, the more weapons which are needed and the more potential for some sort of insider incident.