Good day, and thank you for inviting me.
This is a conference on deterrence, and I am glad to see so many bright people coming together in order to explore its challenges. Deterring large-scale aggression against the United States and its allies has always been the core function of our armed services, and this is no less true for our nuclear forces. But in this nuclear age, doing deterrence right presents special risks and challenges.
It is critical to ensure that a potential adversary sees no viable path to getting his way by force, certainly. At the same time, however, the potential costs of getting things wrong could be so catastrophically high that it is also very important to be continually aware of the sometimes-overlooked stability dynamics of nuclear posture choices.
But let me back up a bit, and offer some background about why I am myself so focused upon such questions. One of our areas of specialization in the Bureau of International Security and Nonproliferation at the State Department is regional security. This includes working with other countries not just to help them be better partners in preventing the further proliferation of weapons of mass destruction, but also to help them develop better — that is, safer and more stable — relationships with each other.
Such diplomatic efforts involve encouraging approaches to regional security that minimize incentives for proliferation, but — where past nonproliferation efforts have been unsuccessful and countries unfortunately have come to possess nuclear weapons — it can also involve working with partners to encourage wiser choices and practices in managing their nuclear status. Let me be clear, this is not to condone proliferation once it occurs; nor am I referring to stability-focused engagements with irresponsible states that have a track record of illegal nuclear weapons work that it is our objective to roll back, such as North Korea or Iran. I mean only to make the point that, in some cases, if proliferation does occur and cannot be reversed, we want states to exercise restraint and make choices regarding nuclear technology, doctrine, and posture that maximize regional — and global — security and stability. This is nuclear risk reduction in the highest sense.
This means, for instance, that while others in the Department handle diplomatic engagements related to America’s own nuclear forces and posture, we in ISN work to encourage other possessor states to make prudent, stabilizing choices in order to avoid catastrophic outcomes. So let’s take a brief trip together down the strategic posture theory rabbit hole.
I. Diplomatic Engagement for Crisis and Arms Race Stability
I should preface these comments, I suppose, by making clear that I make no claim that we are bearers and purveyors of infallible wisdom in these regards; deterrence and escalation theory remain, as they have always been, controversial and contested in many ways. It is also true that every deterrent relationship and every arms competition has its own idiosyncrasies, and that for this reason, it may not necessarily be the case that lessons learned in one arena make sense mutatis mutandis in nuclear weapons relationships that emerge in different contexts.
However, given what is at stake, i.e., the preservation of geopolitical stability and the prevention of nuclear war, we should not shrink from using diplomatic levers to encourage constructive learning wherever possible. One side effect of our long and anxious national history of living in a strategic nuclear dyad of our own — striving to deter aggression, prevent a breakdown in deterrence, extend deterrence to allies, defuse proliferation pressures, limit proliferation opportunities, and preserve crisis stability and unwanted escalation, all at the same time — is that these challenges contributed to the development of a rich ecosystem of strategic thinking about how to walk the deterrence tight rope entailed by trying to do all of these things at at the same time.
At least in the West, where we prized and preserved freedom of thought and expression, there developed over time competing schools of public discourse on strategic issues, a rich academic literature, a diverse infrastructure of competing faculties, think tanks, and academic programs, and a bestiary of inside-the-bureaucracy governmental elements devoted to managing a nuclear relationship without catastrophe. Conferences like this one today, and associative groups such as the Deterrence and Assurance Academic Alliance, make people like you the inheritors of this tradition. This does not mean we got all the answers right, but we certainly have a long history of examining the issues very carefully from multiple perspectives.
So there is surely room for useful engagement and reciprocal learning with our diplomatic partners as they struggle with modern stability challenges. To my eye, perhaps one of the most useful things we must all vigilantly pursue is how to minimize and manage the risk of unwanted escalation – recognizing, of course, that the capability to manipulate risk to achieve political objectives can be a major reason why states acquire nuclear weapons in the first place.
II. Thinking about Stability: Less “How Many?” Than “What? And How?”
In meeting this challenge of minimizing and managing the risk of unwanted escalation, it seems to me that raw numbers may sometimes matter much less than the types of systems each rival possesses and how they are postured against each other. With respect to any other countries’ arms competitions, therefore, there is clearly much room for thoughtful engagement on the complex crisis stability dynamics created by the interplay of possessors’ choices about equipment, posture, and doctrine.
To help such engagements be as productive as they can be and enable those partners to reduce nuclear risks as much as possible for so long as they feel compelled to remain in nuclear weapons relationships, we owe ourselves and our diplomatic partners as much clear thinking and thoughtful consideration as possible about whether, and the degree to which, particular weapons systems, force postures, and doctrinal choices are stabilizing or destabilizing.
So let me give a few examples of how one might think through such stability questions from the perspective of national choices about particular weapons systems. I do not offer these as any kind of Holy Writ, of course, nor with the claim that they are absolutely the only conclusions a reasonable person could reach, nor that these suggested conclusions would necessarily follow in all imaginable arms-competitive contexts. However, I do think these examples have value as illustrations of how one might develop a stability-focused discourse to inform choices between nuclear possessor states.
III. Illustrative Examples
A. Heavy, Many-Warhead, Fixed ICBMs
First, how might one think about the stability impact of traditional, fixed intercontinental ballistic missiles (ICBMs) carrying extremely large numbers of warheads? It became clear during the late Cold War that it was possible to develop very large missiles with as many as 10 or 12 separate warheads, each capable of hitting a different target. Over time, however, people began to have some second thoughts about such monsters, informed by game-theoretical thinking about nuclear crisis stability.
Let’s explore this. If Country X has a large number of warheads co-located in individual missiles, each of which is subject to being destroyed by only one or two of Country Y’s warheads, this could, in a crisis, create a dangerous incentive for a first strike. That unfavorable exchange ratio — several of X’s warheads lost in exchange for perhaps only one of Y’s warheads expended — means that Y has some reason to err on the side of pre-emptive attack, trying to destroy X’s heavy fixed ICBMs before he can use them. If this works, Y might not only have destroyed X’s land-based force rather efficiently, but might indeed also still have plenty of warheads left over for other targets.
At the same time, and for precisely analogous reasons, X himself might have a dangerous incentive in a crisis to launch his missiles first — perhaps even preemptively, or upon the slightest hint of attack warning — not just to go after Y’s own heavy missile silos (if it has them) and thus seize a similar “exchange-ratio bonus” for himself, but also simply because the unfavorable ratio of incoming warheads to target warheads makes it especially dangerous for X to risk “riding out” a possible incoming salvo. Hence traditional, Cold War-style heavy, many-warhead fixed ICBMs are now generally thought to be destabilizing: they seem to maximize incentives for pre-emption and automatic, unthinking launch on warning.
We ourselves used to have heavy, many-warhead silo-based systems, of course, but in U.S. strategic posture across the last few administrations we have moved away from such choices. Although the U.S. Nuclear Posture Review has made clear that a portion of our ICBM force could again be uploaded if there were a need to do so, but we have successfully transitioned our own ICBMs from multi-warhead to single-warhead systems and we have long since abandoned very large, mega-MIRV’d systems such as the Peacekeeper.
If one were to take this game-theoretical insight to heart, it would presumably follow that developing heavy, mega-MIRV’d silo-based ICBMs — such as Russia’s forthcoming Sarmat ICBM — would be a poor strategic choice almost tailor-made to promote crisis instability. Sound and thoughtful diplomacy with countries having their own nuclear arsenals should thus encourage better, more stability-focused approaches.
B. Forward-deployed Battlefield Weapons
As a second example, consider the challenges potentially presented by large numbers of and diversity in small, battlefield nuclear weapons. Such things were deployed in some numbers during much of the Cold War — including some notoriously small, portable systems such as the “Davy Crockett” battlefield rocket that could be mounted on a Jeep, a nuclear artillery shell for an 8-inch Army howitzer, and a man-portable atomic demolition mine. The stability impact of such very short-range (or zero-range!) systems — and the degree to which their use could be reliably controlled in a conflict — has long been questioned, and after careful consideration we ourselves moved emphatically away from them years ago. Many observers fear that such devices deployed close to the anticipated front line in a conflict between nuclear rivals — particularly if authorization for their use is devolved to battlefield commanders, since reliable, centralized command-and-control is usually thought to be essential to crisis management — might lead to inadvertent or dangerously precipitous escalation and early nuclear use.
These dangers arise because such easily-usable weapons deployed very far forward could be targeted preemptively or quickly overrun, the imminence of which might lead to precipitous use. In that case, the result could have strategic consequences (in the form of nuclear combat) triggered by strategically unimportant minor or inconclusive fluctuations in the contours of that front line. Some observers might speculate this could strengthen deterrence, on the theory that such amazing dangers might make an invasion less attractive to an aggressor in the first place.
However, even if such worrying brinksmanship did have value, there would still be huge dangers of losing control. To the degree that control of easily-portable devices were delegated far down the chain of command, this would greatly challenge crisis management and warfighting command and control by national-level authorities. Catastrophically consequential decisions being made under stress by ill-informed junior battlefield commanders who lack the big picture does not bode well for crisis stability.
Stability considerations thus make large numbers of and diversity in small, easily-portable battlefield devices such as nuclear artillery shells or demolition mines seem highly problematic. Such reasoning contributed to decisions by both of the nuclear superpowers to pull non-strategic weapons significantly back from the control of unit commands. This is a compelling logic that other nuclear possessors might also wish to consider.
I would also urge other possessing states to follow the U.S. model of highly centralized and rigorous command and control practices, which promote stability and predictability even in times of crisis — and to avoid either devolved, uncontrollable use controls or mindlessly automated release procedures such as the Dr. Strangelove-style “Perimeter” system for automatically initiating nuclear war. Methods of dispersion in a crisis should also be scrutinized, since such small, portable devices a susceptible to threats from guerrilla or terrorist groups within one’s borders. The implications of deployment modalities and command-and-control questions are not the sort of “sexy” nuclear weapons matters that get much attention from armchair strategists, but they are critical questions for the real professionals, and we should encourage countries with nuclear weapons to think these things through carefully.
C. Context Matters
Third, nuclear powers might also bear in mind that what makes sense in one nuclear context may not make sense in another. I have noted how the risks associated with large numbers of or diversity in small, forward-deployed weapons increase tremendously if they are deployed where guerrillas or terrorists might seize them in the field – which is, if you ask me, a pretty important context-specific factor – but difficulties can also arise with other systems.
If you are a nuclear power engaged in a nuclear weapons relationship with an adversary many thousands of miles away, there’s obviously some logic in acquiring delivery systems with intercontinental range. Participants in a regional dyad, however, should carefully consider limiting the range of their systems to avoid having too much range, which could end up drawing them into deeply problematic provocation dynamics with nuclear powers outside the core deterrence dyad. Such a dynamic would carry with it potentially catastrophic risks of inadvertent escalation, miscalculation, or unlooked-for intervention or pre-emption.
These various challenges are difficult and problematic enough when a relationship remains dyadic, so stumbling into escalatory problems with extra-regional players could be notably unwise, especially if those additional players are very powerful and one does not actually have any particular antecedent strategic-level problem with them in the first place. Nuclear possessors need to think through such dynamics, for it matters whether, and how, one’s own regional nuclear dynamics are connected to, or entangled with, broader ones.
D. Unlimited-range Cruise Missiles
Fourth, I would suggest that exotic new technologies and methods need careful attention as well — because what might initially seem to be an attractive “feature” of a new weapons system could turn out to be, from a stability perspective, very much a dangerous “bug.” As an example, take something as seemingly simple as a weapon system’s range. More range seems like it would always be better, right? Well, not always.
It is at least theoretically possible to develop a nuclear-powered cruise missile that could have an essentially unlimited range. In the late 1950s, for example, U.S. and Soviet researchers both worked on designs for a nuclear-powered airplane, the advantage of which was thought to be its ability to remain “continuously airborne.” The U.S. program was rather sensibly terminated in 1961, and the Soviet concept apparently never even got off the drawing board, but one could at least imagine a cruise missile loosely based upon such technology today. To say that such a thing might be possible, however, is not to say that it would be in any way wise.
For one thing, there might be alarming technical, safety, and humanitarian issues associated with a nuclear reactor flying through the air across intercontinental distances — especially a reactor running hot enough to superheat ingested atmospheric gases for propulsion and probably of necessity lacking much by way of radiation shielding. What would the implications be if it were to crash or be shot down, moreover, especially if its flight route took it for thousands of miles through the airspace of any number of countries? Yet even leaving those obvious concerns aside, it is far from clear that such a system would make any sense whatsoever from a stability perspective. Quite the contrary.
Some strategists might perhaps value such a missile as a strategic delivery system because of its potential ability to arrive over enemy territory at low level and from an unexpected or even unwatched point of the compass after a long and craftily circuitous transit. The extreme range that could make this possible might indeed make defending against such a missile difficult, but that’s hardly the end of the story, and such an apparent advantage would likely be offset by other problems. The possibility of an “infinite-range” cruise device might well be quite destabilizing, and could create a major risk of inadvertent nuclear war — not least because of the weird, but hardly hypothetical, possibility that such a missile could be launched into indefinite-duration “holding pattern” flight paths that might be intended to maximize perceptions of imminent threat in order to facilitate an aggressor’s coercive diplomacy, but that in fact would likely elicit unpredictably escalatory responses and escalation dynamics.
I would think that the moral of this story about the stability externalities of unlimited range is simple: it is foolish to plunge forward in nuclear weapons and delivery system development rashly. Considerations of stability cannot be ignored, and the fact that one can build something does not always mean that one should. Some choices are just bad ones.
E. Transparency and Clarity
Sixth, and finally, I believe there is intrinsic value in offering the kind of transparency that helps provide one’s potential clarity about how one thinks about nuclear weapons. I don’t mean the kind of “transparency” that relates to exactly how many one has, specific details about exactly when one would (or would not) actually use a nuclear weapon, or sensitive details about their deployment. Instead, I’m referring to insight into the basic concepts that underlie one’s nuclear posture and doctrine. Providing reasonable clarity about posture and doctrine can serve the interests both of deterrence and of crisis stability and escalation management, by helping increase predictability and reducing the kinds of uncertainty that may fuel dangerously mistaken assumptions.
This is a kind of transparency that we in the United States provide very publicly with every edition of our Nuclear Posture Review, as well as in periodic public statements, reports, and documents of various varieties. We are, in fact, by far the most transparent of any nuclear weapons possessor in this respect. We make such information public, we explain it to adversaries and onlookers alike, and we defend it in public so that we are as clear as we can be about the role that nuclear weapons play in our defense planning and the reasons for the posture choices we have made.
Nobody else does it like this, but I would argue that they should: the more transparency of this sort, the better. As I noted last year in an event at the Preparatory Committee meeting for the Nuclear Nonproliferation Treaty in Geneva — at which two of us from the U.S. State Department joined representatives from the Office of the Secretary of Defense and the Joint Chiefs of Staff in explaining the latest Nuclear Posture Review — we Americans are deeply transparent about these fundamental conceptual and doctrinal issues, and we challenge other possessors to follow our lead in being that way too.
As I said earlier, I hope no one takes the arguments I have suggested as entirely conclusive. I offer them not as hard and fast conclusions, but as illustrations of a stability-focused thought process. We in the United States engaged in a good deal of such thinking for decades, and we must not forget how to do it. Such ways of thinking may also be worth fostering with and among nuclear powers engaged in their own nuclear weapons relationships.
At any rate, I hope this gets you thinking. To that end, I hope the scholarly and think tank communities can work with us to encourage the development of stability-mindful strategic thinking — and hence real nuclear risk reduction — wherever national leaders find themselves in enduring nuclear weapons relationships. We must all endeavor to prevent our relationships from collapsing into conflict during the presumably still lengthy era still ahead of humanity until – in the phrasing of Article VI of the Nuclear Nonproliferation Treaty – we can ease international tension and strengthen trust between states enough to permit the stable and sustainable elimination of all such weapons.