Conclusion: - Specialized Research AI at MIT

Conclusion:
Strategic Stability & Nuclear War

Christopher F. Chyba & Robert Legvold

I f the fear of nuclear war has faded as the Cold War recedes into the misty past,

we may need to remind ourselves of what these weapons can do. At least five
of the nine countries that currently possess nuclear weapons can deliver thermo
nuclear warheads, each with the explosive equivalent of several hundred thou
sand tons of TNT, nearly halfway around the Earth.1 The intercontinental ballistic
missiles (ICBMs) and submarinelaunched ballistic missiles (SLBMs) that would
deliver them at this range are called “strategic” because they can reach into an
adversary’s homeland to destroy leadership, military, infrastructure, or civilian
targets. Warheads on different missiles are characterized by their yield (explosive
energy) and their accuracy. Estimates in the open literature suggest that the Unit
ed States, for example, can deliver a 455 kiloton warhead launched from a Trident
ballistic missile submarine over six thousand miles to detonate within the length
of a football field of its target.2 The yield of 455 kilotons means that the energy re
leased would equal the explosive energy of 455,000 kilograms (about one million
pounds) of high explosive (TNT), which would be more than thirty times the en
ergy released by the nuclear weapon detonated by the United States over Hiro
shima during World War II. Depending on the relative location of the submarine
launching the SLBM and its intended target, the time between the launch and the
detonation of the warhead could be as short as six to ten minutes.3 An adversary
might have only that much warning time to recognize that an attack was under
way and react.

Some Russian and Chinese strategic missiles are thought to carry warheads of
even larger explosive yields. For example, the Russian SS19 Mod 3 ICBM carries
six independently targetable warheads (MIRVs) that reportedly have a yield as
high as 750 kilotons.4 Figure 1 shows the effects of one such 750kiloton warhead
exploding 1 mile (1.6 kilometers) above New York City, centered on Midtown
Manhattan.5 The four concentric rings in the figure illustrate the effects of the
explosion. Moving outward from the point of detonation: Within the first ring

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Figure 1
Nuclear Blast above Midtown Manhattan

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The map illustrates the immediate consequences of the hypothetical explosion of a 750-kiloton
warhead that detonated 1 mile (1.6 kilometers) over Midtown Manhattan. More than 1.8
million people would be killed nearly instantly, and over 2 million more immediately wounded.
The effects of likely massive urban fires are not included in these casualty estimates, nor are
later deaths from radiation exposure. Source: Alex Wellerstein, NUKEMAP, https://nuclear
secrecy.com/nukemap/. Map data © OpenStreetMap contributors, published under a Creative
Commons Attribution-ShareAlike 2.0 Generic (CC BY-SA 2.0) license; and Imagery © Mapbox.

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(radius 2.5 kilometers) the blast is so strong that even heavily built concrete build
ings are demolished. Virtually every person within this area is killed in the blast.
This ring extends entirely across the island of Manhattan from the East River to
the Hudson. The second ring (radius 5.7 kilometers) reaches into New Jersey and
the boroughs of Brooklyn and Queens. It marks the distance out to which residen
tial buildings collapse. At this distance, “injuries are universal and fatalities are
widespread.” The third ring (radius 11 kilometers) shows the effects of the imme
diate thermal radiation (high intensity ultraviolet, visible, and infrared light emit
ted by the explosion). Out to this distance, anyone with a line of sight to the deto
nation suffers thirddegree burns to exposed skin. Finally, the fourth ring (radius
15 kilometers) marks the distance out to which windows shatter, with resulting
injuries from flying glass. Overall, more than 1.8 million people would be killed
nearly instantly, and over 2 million more immediately wounded. These numbers
ignore the effects of firestorms–massive urban fires driven by hurricaneforce
winds that may result from the nuclear detonation6–as well as longerterm radi
ation and fallout. Of course, many hospitals and firehouses would be destroyed,
and many medical personnel immediately killed, limiting the lifesaving potential
of firstresponders.

These results are for a single large strategic warhead. Under the 2011 New
START arms control treaty, Russia and the United States agreed to reduce their
numbers of deployed strategic warheads to 1,550 on each side.7 China, France, and
the United Kingdom have smaller numbers of warheads on missiles, estimated at
about 290, 300, and 225 warheads, respectively.8 In a nuclear war, or a convention
al war that escalated to the use of strategic nuclear weapons, many–perhaps hun
dreds or more–such detonations might take place.

T his must never be allowed to happen. One way to try to ensure that it

never does is to threaten nucleararmed adversaries with nuclear retali
ation from forces that would credibly survive an initial attack (the “first
strike”). Potential attackers would then presumably be deterred from launching
a first strike because they would feel certain to suffer devastating nuclear retalia
tion.9 Yet this deterrent posture carries with it an inescapable, perhaps small but
difficult to quantify, possibility of inadvertent or mistaken nuclear war.10

Another way to try to ensure that the worst never happens is to eliminate all
nuclear weapons worldwide. But this approach raises its own challenges. One
is how to reduce and then eliminate nuclear weapons with sufficient verifica
tion that all countries could feel confident that no weapons were hidden in vio
lation of the disarmament agreements. A second is that weapons knowhow can
not be unlearned and relevant capabilities fully undone, so that in a major war or
political crisis, there could be pressure to recreate rapidly and perhaps preemp
tively use nuclear weapons. That is, a world of zero nuclear weapons could prove

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Dædalus, the Journal of the American Academy of Arts & SciencesStrategic Stability & Nuclear War

dangerously unstable. Experts have dedicated much attention to these challeng
es, but they are far from solved.11 At the same time, as this volume of Dædalus has
highlighted, a future world in which stability is preserved through nuclear deter
rence also faces considerable known and unknown challenges.

But there are other possible security catastrophes that states also wish to pre
vent: for example, fullscale conventional war among the major powers. World
War II resulted in the deaths of over sixty million people.12 The major powers have
not waged total war against one another since 1945, even if many other smaller
conflicts have been fought. There is more than one reason for this “Long Peace,”
but it is likely that the existence of nuclear weapons has induced caution on the
part of the major powers over being drawn into major war.13 The successful mat
ing of fusion warheads to ICBMs or SLBMs has for this reason been termed the
“nuclear revolution,” because the likelihood of major war among states equipped
with these weapons has been, some argue, greatly reduced by removing any doubt
in the minds of national leaders about the horrific outcome of such a war.14 Ballis
tic missile defense systems remain all but useless against more than a small num
ber of incoming strategic warheads, so there is no reliable defense.15 Therefore, in
a faceoff among nucleararmed states, rational leaders provided with competent
technical information must recognize that their country lies open to destruction.
There is no denying the devastating consequences of thermonuclear war. Since
fullscale conventional war could escalate to nuclear war, rational leaders would
not risk waging fullscale war on another ICBM or SLBMwielding thermonuclear
power.16 And so, as some have argued, peace at this level has endured.

Various countries at various times have claimed other vital uses for nuclear
weapons. Before it gave up its small, indigenous nuclear weapons arsenal, apart
heid South Africa imagined that threatening the use of its weapons would force
the great powers to negotiate an end to any conflict that menaced it.17 Pakistan’s
senior generals have been clear that Pakistan would use nuclear weapons first if
needed to repel a purely conventional Indian invasion.18 It seems likely that North
Korea’s Kim Jongun views the threat to use his country’s nuclear weapons as his
ultimate guarantor of regime and personal survival.19 Finally, some countries, at
least under certain leaders, may have pursued nuclear superiority (more nuclear
missiles, with more nuclear warheads, say, than one’s adversary) under the belief
that this putative superiority in itself would confer other advantages or intimidate
adversaries away from certain courses of action.20 Not unrelatedly, some coun
tries may pursue nuclear weapons to protect themselves against the possibility of
nuclear blackmail or coercion.21

A nd so, we find ourselves in our current dilemma. Countries desire the se

curity afforded by their own or their allies’ nuclear weapons, but as long
as these weapons exist, there remains a chance that they could be used in

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149 (2) Spring 2020Christopher F. Chyba & Robert Legvold

limited or even vast numbers. This could result from escalation in the context of
an ongoing conventional war, with one side concluding it had no choice but to
strike first; or it might result from an erroneous conclusion made under time pres
sure that another state has launched a nuclear attack; or from a miscalculation by
a leader who is not realistically informed or who has rebuffed efforts to be so in
formed; or even via an irrational leader coming to power and making heinous de
cisions. It is sobering that since the end of World War II, nuclear adversaries have
considered the use of nuclear weapons in preventive war, have explicitly or im
plicitly threatened the use of nuclear weapons, and, in the Cuban missile crisis,
have come close to misjudgments that would have led to nuclear war.22 Concerns
over escalation to the use of nuclear weapons are therefore justified by the histor
ical record. At the same time, there has been no wartime use of nuclear weapons
and no fullscale war between major powers since 1945.

Nucleararmed states have aimed to reduce the likelihood of the various path
ways to nuclear weapons use by seeking to create conditions of strategic stability.
Strategic stability is usually taken to include both crisis stability and arms race sta
bility. Crisis stability means that even in a conventional war or faced with a possible
nuclear attack, states would not use nuclear weapons for fear that such escalation
would bring certain disaster. Crisis stability must be robust even against inadver
tent or mistaken nuclear escalation. Arms race stability means that nuclear powers
do not have incentives to pursue weapons or weapon deployments resulting in
actionreaction cycles that undermine crisis stability.

The goal of this volume has been to examine whether current directions in in
ternational affairs and a concomitant technological evolution are eroding strate
gic stability and placing the world at greater risk of nuclear weapons use–and if
so, what might be done about it. In particular, this volume had its genesis in three
particular concerns that appear to threaten strategic stability: the increasing com
plexity of nuclear relationships in a world of multiple and increasingly capable
nuclear powers; the nearcollapse of bilateral strategic arms control between the
United States and Russia; and the development and possible deployment of new
technologies whose characteristics overall seem likely to be destabilizing. Sepa
rately or combined, each of these trends could make escalation to nuclear weap
ons use more likely. These are wideranging multilateral challenges, but this vol
ume has focused primarily on the triangular relationship among China, Russia,
and the United States, with only occasional discussion of other nuclear powers.
This reflects a practical decision to begin with these core relationships, not a belief
that only those relationships matter. Subsequent work will expand this focus.23

During the Cold War, countries looked to a variety of means to prevent esca
lation to nuclear war, without forsaking what they perceived as the security ben
efits of their nuclear arsenals. The dream of a successful defense against a large
scale nuclear attack never ended, but the technical reality remained that warheads

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Dædalus, the Journal of the American Academy of Arts & SciencesStrategic Stability & Nuclear War

launched from ICBMs and SLBMs were extremely difficult to intercept, and that
an attacker’s countermeasures were technically simpler and less expensive than
a defender’s interceptors.24 Absent a credible defense against strategic missiles,
other approaches came to the fore.

The least subtle of these was deterrence. In broad terms, deterrence in the nu
clear context seeks to alter an adversary’s costbenefit calculation with respect
to the use of nuclear weapons.25 Its most stark realization was in the condition
of mutual assured destruction (MAD) between the United States and the Soviet
Union. Once secure secondstrike systems were in place, each side understood
that fullscale nuclear war would mean mutual annihilation, regardless of who
struck first. Each country was deterred, they hoped, from reaching for the nu
clear trigger by a recognition that no conceivable benefit was worth this level of
“assured destruction.”

In less stark manifestations of deterrence, countries sought to supplement the
threat of punishment with steps that would deny an adversary’s efforts to achieve
their goals in launching an attack: socalled deterrence by denial. For example,
an adversary might imagine that smallscale nuclear weapons could be employed
in limited fashion to secure a desired objective without leading to unacceptable
further escalation. Deterrence by denial meant fashioning capabilities that would
dissuade an adversary from trying, thus cutting off a dangerous path to even great
er nuclear weapons use. If nuclear weapons were nevertheless used in a limited
way, some theorists argued that adversaries, faced with an opponent whose esca
latory options were superior, might still be deterred from moving to higher levels
of nuclear destruction.26

Beyond deterrence, the United States and the Soviet Union, and then Russia,
engaged in a variety of arms control measures that were intended to reduce the in
centives either side might have for escalating to nuclear weapons use.27 Arms con
trol sought to improve the adversaries’ knowledge of one another, both through
technical transparency into each other’s military capabilities and by enhancing
leadership communication in crisis. Consequently, escalation through fear, misun
derstanding, or worstcase analyses would be less likely. Jon Wolfsthal, in his essay
for this volume, highlights several major U.S.Soviet arms control treaties that em
bodied these objectives.28 The 1972 AntiBallistic Missile (ABM) Treaty sought to
limit strategic missile defense deployments to spare each side a costly defensive
arms race that could, at its worst, provide the false impression that launching a
first nuclear strike was credible due to an effective defense against an adversary’s
reply. The 1987 Intermediate Nuclear Forces Agreement (INF) stabilized the U.S.
Russian nuclear relationship by eliminating the two countries’ intermediate range
nuclear missiles in Europe and elsewhere, thereby freeing Moscow and European
capitals from the fear of nuclear destruction from a nonstrategic missile that, be
cause of the shorter ranges involved, could eliminate leadership, command and

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149 (2) Spring 2020Christopher F. Chyba & Robert Legvold

control, or other targets with warning times much shorter than those of ICBMs.
The second Strategic Arms Reduction Treaty (START II), signed by the United
States and the Russian Federation in 1993, required the removal of MIRVed war
heads from ICBMs. This would have reduced incentives for a first strike against
vulnerable landbased missiles hosting multiple warheads. (The treaty, however,
never entered into force.) All these agreements instantiate a view of arms control
motivated by the desire to enhance strategic stability, rather than the intention to
reduce the size of nuclear arsenals as such. Yet there were also arms control agree
ments that seemed more concerned with simple measures of parity than with en
hancing stability.29

As the archives open, we are learning that the impulses prompting leadership
in the two countries to turn to arms control were as broadly political as they were
an effort to manage nuclear risks. James Cameron, in his essay in this volume,
stresses this larger geopolitical context for arms control. Perhaps this should be
unsurprising, since such a longlasting foreign policy tool might be expected to
serve many constituencies in order to survive over many decades. Cameron ar
gues in particular that arms control, including the 1970 Treaty on the NonProlif
eration of Nuclear Weapons (NPT), was used by the United States and the Soviet
Union “to preserve their dominance of global politics at the expense of their al
lies’ military options.”30 Similarly, as he and other historians have shown, bring
ing U.S. allies under the protection of its nuclear umbrella was a powerful way
to avert nuclear proliferation among those allies. In particular, both the United
States and the Soviet Union valued the 1963 Limited Test Ban Treaty as a barrier
to Germany pursuing a nuclear option. The crucial interplay between deterrent
practices and arms control in the pursuit of broader objectives did not cease with
the end of the Cold War. Looking ahead, if nuclear arms control is to have a future
not only between the United States and Russia but among the other major nucle
ar powers, it will only be if leaders see it as a way to achieve larger geopolitical ob
jectives as well as a safer nuclear world.

Another view of the nuclear threat, one whose roots reach back to some of the
scientists who produced the first atomic bomb, was that measures such as deter
rence and arms control could not guarantee strategic stability in perpetuity, and
that international security ultimately would require the elimination of nuclear
weapons.31 The recognition that nuclear weapons bring peril as well as stability was
one motive behind Article VI of the NPT, which calls for their ultimate elimina
tion.32 Throughout the Cold War, there was an ebb and flow of efforts by elements
of civil society or on the part of nonnuclearweapon states to pursue internation
al security though nuclear disarmament.33 The focus in this volume on relations
among and strategic approaches of the three leading nuclearweapon states–the
United States, Russia, and China–risks paying too little attention to the views of
nonnuclearweapon states who find the continuing strategic faceoff (claims for

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Dædalus, the Journal of the American Academy of Arts & SciencesStrategic Stability & Nuclear War

the efficacy of deterrence or no) to be deeply troubling. Harald Müller and Car
men Wunderlich, in their essay discussing the Treaty on the Prohibition of Nuclear
Weapons, trace the ways in which the apparent lack of attention on the part of the
nuclearweapon states to their Article VI NPT commitments and their backtrack
ing on past commitments have encouraged 122 nations to negotiate–though not
yet bring into force–a treaty to ban nuclear weapons altogether.34

A ll these approaches to maintaining strategic stability have been affect

ed by the transition from the largely bilateral nuclear rivalry of the Cold
War to today’s more complicated nuclear world. Disturbingly, the trends
we identify here–increasingly complex relations among increasingly capable
nucleararmed states, the collapse of formal arms control, destabilizing techno
logical advances–are not merely moving in parallel, but may reinforce one anoth
er in powerful ways. Steven Miller, in his lead essay for this volume, argues that
the effects of the transition from a predominantly U.S.Russian nuclear weapons
relationship to a ChineseRussianU.S. nuclear triangle can already be seen in im
portant outcomes.35 Miller argues that while accusations of treaty noncompliance
were the proximate cause of U.S. withdrawal from the INF, strategic calculations
reflecting the more complicated threeway ChineseRussianU.S. relationship
undergirded this decision: because of the bilateral INF treaty, neither Russia nor
the United States could match China’s growing missile capabilities in the 500–
5,500 kilometer range. A bilateral treaty was no longer well suited for a trilateral
military relationship.

Miller gives a second example of increasing complexity due to multilateral nu
clear decisionmaking. In the case of ballistic missile defense, steps taken by the
United States to defend itself against small numbers of North Korean ICBMs or
(possible future) Iranian ICBMs are seen by China and Russia as laying the ground
work for a more extensive and effective system to counter their own strategic nu
clear forces. (And, Miller argues, the Trump administration has given them addi
tional cause for this interpretation.) Steps taken in response by China will poten
tially affect India’s decisions about its own nuclear forces. Beijing sits at an apex
of two nuclear triangles, one with the United States and Russia, the other with In
dia and Pakistan. At a minimum, as Miller approvingly quotes former Ambassa
dor Steven Pifer, “Strategic stability appears increasingly a multilateral and multi
domain construct.”36 Miller is doubtless correct when he concludes that formal
treatybased bilateral arms control, a classic tool for managing strategic stability,
is less and less suited for the world in which we now live. Nor is multilateral arms
control likely to fill the void. As Miller warns: “Bilateral arms control is collapsing
but seems in any case insufficient; trilateral arms control seems necessary but so
far remains impossible; multilateral arms control is comatose; and regional arms
control is desirable but is as yet nonexistent.”37

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149 (2) Spring 2020Christopher F. Chyba & Robert Legvold

Any successful path forward will depend on the United States, Russia, and Chi
na finding some measure of common ground. If the essays in this volume by Anya
Loukianova Fink and Olga Oliker, Li Bin, and Brad Roberts make one thing clear,
that will not be easy. Reconstructing the perspectives of Russia, China, and the
United States, respectively, the authors each describe a set of concerns fundamen
tally at odds with those of at least one of the other two. For Roberts, striving to
pursue an approach to nuclear deterrence that lowers the risk of nuclear war re
mains key for the United States, but the context in which the United States must
conduct this pursuit is altogether different. Russia, he argues, is no longer a poten
tial partner in seeking to reduce nuclear risks, but a dangerous adversary striving
to create a nuclear posture serving its aggressive foreign policy agenda.38 The risk
to be averted, therefore, is first and foremost that U.S. deterrence will fall short.
By Fink and Oliker’s retelling, Russia, in contrast, sees the situation in reverse:
Russia’s nuclear forces are designed to deter the primary threat posed by the Unit
ed States. As its once dominant role in a shifting global setting fades, Russia’s lead
ership contends, the United States counts on its military power, underpinned by
nuclear weapons, to threaten and coerce others. It seeks nuclear superiority and
now focuses on new technologies and weapons systems intended to degrade the
Russian nuclear deterrent and make nuclear weapons more usable.39

Not only have U.S. and Russian views on what threatens strategic stability
sharply diverged, making preserving, let alone extending, the nuclear arms con
trol process a fading prospect, but the way each side now both defines the spe
cific threat that it sees in the other side’s weapons programs and doctrinal shifts
and prepares to counter them seems likely to increase the chance of inadver
tent escalation across the nuclear threshold. In the meantime, Li argues, the dis
parity between the size of the U.S. and Russian nuclear arsenals and those of
all other countries means that the numerical aspects of U.S.Russian arms con
trol treaties “cannot apply to China.”40 In other words, formal multilateral arms
control is, as Miller suggested, not currently an available option. As the Unit
ed States begins to treat China as a rising geopolitical threat and its enhanced
nuclear forces as a source of concern, China’s changing perceptions of global
trends, the nature of the nuclear world, and the challenges it faces, according to
Li, widens the gulf.

Complicating all issues of mutual understanding and potential escalation is
the arrival–likely in the absence of any related arms control measures–of a set
of new technologies that overall will probably make nuclear forces and their as
sociated command and control appear more vulnerable. The most immediate
of these is cyberspace operations. In his essay, James Acton systematically de
scribes the ways in which cyber weapons differ from traditional weapons and, in
particular, those aspects of cyber operations that seem especially destabilizing.41
He acknowledges, however, that credible approaches to mitigate this threat are

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inadequate to the need. Christopher Chyba, in his essay, examines a wide range
of new technologies, and proposes a framework to think through a given technol
ogy’s impact on strategic stability. The intent of his framework is to help ensure
that consideration (by any country) of new technologies systematically confronts
the variety of ways in which destabilizing effects may result, so that possible miti
gating steps can at least be considered.42

How, then, are we to work within this world to lessen the chances of escala
tion to the use of nuclear weapons? Most of our authors propose elements of a re
sponse, but Linton Brooks, James Timbie, and Nina Tannenwald, in their essays,
take this question as their primary focus. There is consensus that the United States
and Russia should take advantage of New START’s provision that allows the two
parties to extend the treaty by five years beyond its looming 2021 expiration dead
line. Brooks emphasizes that the transparency and predictability measures im
plemented in New START benefit the United States more than Russia because the
United States is inherently the more open of the two countries. Moreover, while
much of the information exchanged between the two sides could be obtained by na
tional intelligence, this would require the diversion of these resources away from
other intelligence requirements. And still, some of the information provided by
New START, Brooks warns, “cannot be obtained in any other way.”43

Yet Brooks–in agreement with other authors in this volume–acknowledges
that a replacement treaty is nevertheless unlikely.44 Timbie is clear about why fur
ther arms control treaties of any kind between Russia and the United States seem
improbable. “Russia,” he notes, “has taken the position that further agreements
must address thirdcountry forces, missile defense, and precision conventional
systems.”45 But it is unlikely that China will agree to enter a formal treaty pro
cess, and the United States is unlikely to negotiate treaty commitments limiting
missile defense. To this, one might add the seeming unwillingness of the current
U.S. Senate to ratify treaties of nearly any kind, and arms control treaties in
particular.

With the end of New START, bilateral arms control between the United States
and Russia in the sense of formal legally binding treaties comes to an end. Brooks
emphasizes that it is important to analyze carefully what the consequences of
this loss of information and restraint will be, and to understand what mitigat
ing steps may be taken to compensate for at least some of what will be lost. To
this end, Timbie proposes an extensive list of transparency measures, numerical
limits, and constraints on behavior that could be agreed upon as political, rather
than legal, agreements. Verification would of necessity be weaker than with New
START, but perhaps some limited verification measures could nevertheless be put
in place. This would circumvent the U.S. treatyratification problem, even if the
agreements are more fragile, more easily repudiated by incoming presidential
administrations, and less well verified. Given the Russian concerns that Timbie

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himself identifies, it is unclear how realistic these proposals may be. But at the
least, they should be vigorously explored.

With the decline of treatybased arms control among the nuclearweapon pow
ers, Tannenwald calls for all nucleararmed states to move toward a “regime of nu
clear restraint and responsibility.”46 Restraint, in her view, should “primarily take
the form of reciprocal commitments and unilateral measures to avoid an arms race
and reduce nuclear dangers.” And responsibility means committing to “responsible
deterrence,” which not only prioritizes strategic stability and the immediate goal of
preventing nuclear war but retains the ultimate goal of disarmament. Nuclear dis
armament is, after all, a treaty requirement that the United States accepted when it
ratified the NPT for, as Article VI of the U.S. Constitution states, ratified treaties are
“the supreme law of the land.”47 Nevertheless, the willingness of the United States
publicly to embrace this obligation has varied greatly from administration to admin
istration, and in the current state of affairs, this “ultimate” goal may seem very dis
tant indeed. In the meantime, Tannenwald suggests a series of measures that could
be pursued absent formal treaties, some by all nucleararmed states, some by the
United States, Russia, and China, and some unilaterally by the United States. One
challenge is to ensure that unilateral measures would be effective beyond just the
United States, France, and the United Kingdom. We see Tannenwald’s suggestions
as reinforcing the calls by Müller and Wunderlich for the advocates of the Treaty on
the Prohibition of Nuclear Weapons and the advocates of deterrence to work harder
to find common ground to prevent the worst outcomes from coming to pass.

T he authors of this volume bring a diversity of views to the issue of strategic

stability in this new multipolar world. Nevertheless, there is broad, albeit
not universal, agreement on several points:

1) Russia and the United States should extend New START’s expiration date
from 2021 to 2026. They should then use that time to pursue a successor treaty that
would further extend the transparency, predictability, and numerical limits (and
ideally, lower limits) that New START provides. Yet most authors of this volume
fear that extension is not likely, and that even if the treaty were extended, a formal
successor treaty is unlikely to be realized.

2) If formal bilateral arms control treaties prove impossible, Russia and the
United States should work to put in place politically binding agreements to cap
ture much of the security and stability benefits that will be lost with the formal
treaty process. However challenging such agreements may prove to be, the two
states should vigorously explore these options.

3) On a bilateral or a multilateral basis, the United States, Russia, and China
should pursue discussions intended to improve understanding of one another’s
strategic concerns and views on which actions by an adversary would be especial
ly concerning or dangerous. Until that happens, the widening gap in the outlook

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and actions of these three major actors will only make this new nuclear environ
ment less manageable and more dangerous.

4) China, Russia, and the United States should also actively work to see whether
and where common ground can be found concerning efforts to mitigate arms spi
rals and restrain the development, deployment, or use of destabilizing technologies.
They should then pursue politically binding agreements to advance these goals, al
beit with a clear eye to the limits of verification that would exist in this format.

In addition, we embrace certain recommendations that were made by individ

ual or a few authors:

5) The United States should strengthen resilience in its many forms–including
to early warning, command and control, and communications–as a key mecha
nism both for deterrence (by denial) and for mitigating the risk of escalation of
nonconventional attacks (such as cyber or bioattacks) or conventional warfare
(including attacks in space) to the use of nuclear weapons.48

6) While military intelligence and operations will increasingly incorporate ar
tificial intelligence (AI) into the interpretation of large amounts of empirical data,
AI should nevertheless not be allowed, either intentionally or inadvertently, to en
ter or creep into actual decisionmaking for nuclear weapons use.

7) Little is to be gained, and perhaps much lost, by insisting on the opposition
between those who emphasize deterrence as the central element of strategic sta
bility and those who see a necessity for nuclear disarmament. In the U.S.Russian
Chinese context, steps that would enhance stability by constraining weapons
numbers or deployment of specific destabilizing technologies, or by improving
communication regarding concerns about, and likely responses to, an adversary’s
possible strategic or tactical actions, could serve both causes.

T he world has lived with nuclear weapons for seventyfive years. Although

the number of states with nuclear weapons has grown slowly, the weapons
themselves, while being used for many purposes, have not been detonat
ed in war since the end of World War II. But the new era we have entered is more
complex, both politically and technically, and seems likely to be less constrained
by treaty, and therefore less transparent and less predictable, than any time in the
past halfcentury.

It remains possible that New START can be extended and continue to serve as
one basis for bilateral stability between the United States and Russia. In this fu
ture, there would remain many dangers, and the United States, Russia, and Chi
na would still need to engage in extensive dialogue to mitigate and manage them.
Absent New START, the challenges would prove much greater. This volume has
attempted, first, to help us understand what this coming world may look like and,
second, to present recommendations that may provide a modest beginning to
avoiding the worst outcomes in these possible futures.

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149 (2) Spring 2020Christopher F. Chyba & Robert Legvold

about the authors

Christopher F. Chyba is Professor of Astrophysical Sciences and International
Affairs at Princeton University. He is Cochair of the “Meeting the Challenges of the
New Nuclear Age” project at the American Academy, and has previously served on
the staffs of the National Security Council and the Office of Science and Technol-
ogy Policy, and as a member of the President’s Council of Advisors on Science and
Technology.

Robert Legvold, a Fellow of the American Academy since 2005, is the Marshall D.
Shulman Professor Emeritus at Columbia University. He is Cochair of the “Meet-
ing the Challenges of the New Nuclear Age” project at the American Academy, for
which he wrote the research papers “Contemplating Strategic Stability in a Multi-
polar Nuclear World” (2019) and “Meeting the Challenges of the New Nuclear Age:
Nuclear Weapons in a Changing Global Order” (with Steven E. Miller and Law-
rence Freedman, 2019). His most recent book is Return to Cold War (2016).

endnotes

1 First-generation nuclear weapons split the nuclei of either high-enriched uranium or
plutonium to produce a million times more energy per kilogram than is the case for
chemical high explosives. These are called fission weapons. Even greater amounts of
energy per kilogram, by perhaps another factor of one hundred, is produced in fusion
weapons. These weapons (also called hydrogen or thermonuclear weapons) use a fis-
sion weapon trigger (or “primary”) to create the pressures and temperatures needed to
fuse hydrogen nuclei together (in the “secondary”) to produce helium, releasing even
greater amounts of energy and typically driving additional fission as well. See, for ex-
ample, Kosta Tsipis, Arsenal: Understanding Weapons in the Nuclear Age (New York: Simon
& Schuster, 1983).

2 Hans M. Kristensen and Matt Korda, “United States Nuclear Forces, 2020,”Bulletin of the

Atomic Scientists 76 (1) (2020): 46–60.

3 See Tsipis, Arsenal, chap. 7.

4 See ibid., chap. 5; and Center for Strategic and International Studies Missile Defense
Project, “SS-19 ‘Stiletto,’” Missile Threat, August 10, 2016, https://missilethreat.csis
.org/missile/ss-19/ (last modified June 15, 2018); compare to Hans M. Kristensen and
Matt Korda, “Russian Nuclear Forces, 2019,” Bulletin of the Atomic Scientists 75 (2) (2019):
73–84.

5 Alex Wellerstein, NUKEMAP, https://nuclearsecrecy.com/nukemap/. Nuclear weapons
effects based on E. Royce Fletcher, Ray W. Albright, Robert F. D. Perret, et al., Nuclear
Bomb Effects Computer (Including Slide-Rule Design and Curve Fits for Weapons Effects), CEX-62.2
(Washington, D.C.: U.S. Atomic Energy Commission Civil Effects Test Operations,
1963); and Samuel Glasstone and Philip J. Dolan, The Effects of Nuclear Weapons (Wash-
ington, D.C.: U.S. Department of Defense and U.S. Department of Energy, 1977).
6 Such as was created at Hiroshima, and also by conventional bombing of cities such as
Dresden, Hamburg, and Tokyo. See Lynn Eden, Whole World on Fire: Organizations, Knowl-
edge, and Nuclear Weapons Devastation (Ithaca, N.Y.: Cornell University Press, 2006).

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7 The actual numbers are somewhat higher, since the counting rules under New START
treat each strategic bomber as delivering only one warhead. See The Treaty between
the United States of America and the Russian Federation on Measures for the Further
Reduction and Limitation of Strategic Offensive Arms (New START Treaty), Article III,
https://2009-2017.state.gov/t/avc/newstart/c44126.htm.

8 Hans M. Kristensen and Matt Korda, “Chinese Nuclear Forces, 2019,” Bulletin of the Atom-
ic Scientists 75 (4) (2019); Hans M. Kristensen and Matt Korda, “French Nuclear Forces,
2019,” Bulletin of the Atomic Scientists 75 (1) (2019): 51–55; and Robert S. Norris and Hans M.
Kristensen, “The British Nuclear Stockpile, 1953–2013,” Bulletin of the Atomic Scientists 69
(4) (2013): 69–75.

9 The essays in this volume have focused (albeit not exclusively) on nuclear deterrence
among the United States, Russia, and China. Not every nuclear power has adopted
a posture of assured retaliation. See Vipin Narang, Nuclear Strategy in the Modern Era:
Regional Powers and International Conflict (Princeton, N.J.: Princeton University Press, 2014).
10 Barry R. Posen, Inadvertent Escalation: Conventional War and Nuclear Risks (Ithaca, N.Y.: Cor-

nell University Press, 1991).

11 See, for example, Joseph Rotblat, Jack Steinberger, and Bhalchandra Udgaonkar, A Nuclear-
Weapon-Free World: Desirable? Feasible? (San Francisco: Westview Press, 1993); George
Perkovich and James M. Acton, eds., Abolishing Nuclear Weapons: A Debate (Washington,
D.C.: Carnegie Endowment for International Peace, 2009); and George P. Shultz, Sid-
ney D. Drell, and James E. Goodby, eds., Deterrence: Its Past and Future (Stanford, Calif.:
Hoover Institution Press, 2011).

12 Antony Beevor, The Second World War (New York: Little, Brown & Co., 2012).
13 John Lewis Gaddis concludes: “It seems inescapable that what has really made the differ-
ence in inducing this unaccustomed caution has been the workings of the nuclear de-
terrent.” See John Lewis Gaddis, “The Long Peace: Elements of Stability in the Postwar
International System,” International Security 10 (4) (1986): 99–142, and references there-
in. Ward Wilson is skeptical of this conclusion; see Ward Wilson, “The Myth of Nu-
clear Deterrence,” Nonproliferation Review 15 (3) (2008): 421–439. See also Robert Rauch-
haus, “Evaluating the Nuclear Peace Hypothesis: A Quantitative Approach,” Journal of
Conflict Resolution 53 (2) (2009): 258–277.

14 Robert Jervis, The Meaning of the Nuclear Revolution: Statecraft and the Prospect of Armageddon

(Ithaca, N.Y.: Cornell University Press, 1989).

15 Dietrich Schroeer, Science, Technology, and the Nuclear Arms Race (Hoboken, N.J.: John Wiley

& Sons, 1984), chap. 10.

16 Confidence in the unwillingness of nuclear powers to go to full-scale war might, however,
encourage these same powers to risk lower levels of conflict or violence: the “stability-
instability paradox.” See Glenn Snyder, “The Balance of Power and the Balance of Ter-
ror,” in Balance of Power, ed. Paul Seabury (San Francisco: Chandler, 1965); and Rauch-
haus, “Evaluating the Nuclear Peace Hypothesis.”

17 Anthony Liberman, “The Rise and Fall of the South African Bomb,” International Security

26 (2) (2001): 45–86.

18 Sadia Tasleem, Pakistan’s Nuclear Use Doctrine (Washington, D.C: Carnegie Endowment
for International Peace, 2016), https://carnegieendowment.org/2016/06/30/pakistan
-s-nuclear-use-doctrine-pub-63913.

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19 Scott D. Sagan, “The Korean Missile Crisis: Why Deterrence Is Still the Best Option,”
Foreign Affairs 96 (6) (2017): 72–82; and Patrick McEachern, “More than Regime Surviv-
al,” North Korea Review 14 (1) (2018): 115–118.

20 See Matthew Kroenig, “Nuclear Superiority and the Balance of Resolve: Explaining Nu-
clear Crisis Outcomes,” International Organization 67 (1) (2013): 141–171. For a contrary
argument, compare with Todd Sechser and Matthew Fuhrmann, Nuclear Weapons and
Coercive Diplomacy (Cambridge: Cambridge University Press, 2017).

21 Major General Yang Huon, former deputy commander of China’s strategic rocket forces,
has written that “China’s strategic nuclear weapons were developed because of the be-
lief that hegemonic power will continue to use nuclear threats and nuclear blackmail.”
Yang Huon, “China’s Strategic Nuclear Weapons,” https://fas.org/nuke/guide/china/
doctrine/huan.htm.

22 See, for example, Lyle J. Goldstein, Preventive Attack and Weapons of Mass Destruction (Stan-
ford, Calif.: Stanford University Press, 2006). See also William Perry, “The Risk of
‘Blundering’ into Nuclear War: Lessons from the Cuban Missile Crisis,” Arms Con-
trol Today, December 2017, https://www.armscontrol.org/act/2017-12/features/risk
-‘blundering’-into-nuclear-war-lessons-cuban-missile-crisis; and Graham Allison, “The
Cuban Missile Crisis at 50: Lessons for U.S. Foreign Policy Today,” Foreign Affairs 91 (4)
(2012): 11–16, https://www.foreignaffairs.com/articles/cuba/2012-07-01/cuban-missile
-crisis-50.

23 American Academy of Arts and Sciences, “Deterrence and the New Nuclear States,”
project chairs Scott D. Sagan and Vipin Narang, https://www.amacad.org/project/
deterrence-and-new-nuclear-states.

24 Schroeer, Science, Technology, and the Nuclear Arms Race; and David Hafemeister, Physics of
Societal Issues: Calculations on National Security, Environment, and Energy (New York: Spring-
er, 2007), chap. 3.

25 Glenn H. Snyder, “Deterrence and Defense,” in The Use of Force: Military Power and Inter-
national Politics, 3rd ed., ed. Robert J. Art and Kenneth N. Waltz (New York: University
Press of America, 1983), 25–43.

26 Herman Kahn, On Escalation: Metaphors and Scenarios (Westport, Conn.: Greenwood Press,

1965).

27 Thomas C. Schelling and Morton H. Halperin, Strategy and Arms Control (New York: Twen-

tieth Century Fund, 1961); and “Arms Control,” Dædalus 89 (4) (Fall 1960)
28 Jon Brook Wolfsthal, “Why Arms Control?” Dædalus 149 (2) (Spring 2020).
29 Thomas C. Schelling, “What Went Wrong with Arms Control?” Foreign Affairs 64 (2)

(1985): 219–233.

30 James Cameron, “What History Can Teach,” Dædalus 149 (2) (Spring 2020).
31 See, for example, Dexter Masters and Katherine Way, eds., One World or None: A Report

to the Public on the Full Meaning of the Atomic Bomb (New York: McGraw-Hill, 1946).

32 Article VI of the NPT reads, in its entirety, “Each of the Parties to the Treaty undertakes
to pursue negotiations in good faith on effective measures relating to cessation of the
nuclear arms race at an early date and to nuclear disarmament, and on a treaty on gen-
eral and complete disarmament under strict and effective international control.” See
“Treaty on the Non-Proliferation of Nuclear Weapons (NPT),” https://www.un.org/
disarmament/wmd/nuclear/npt/text.

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33 Matthew Evangelista, Unarmed Forces: The Transnational Movement to End the Cold War

(Ithaca, N.Y.: Cornell University Press, 1999).

34 Harald Müller and Carmen Wunderlich, “Nuclear Disarmament without the Nuclear-
Weapon States: The Nuclear Weapon Ban Treaty,” Dædalus 149 (2) (Spring 2020).
35 Steven E. Miller, “A Nuclear World Transformed: The Rise of Multilateral Disorder,”

Dædalus 149 (2) (Spring 2020).

36 As quoted in ibid.
37 Ibid.
38 Brad Roberts, “On Adapting Nuclear Deterrence to Reduce Nuclear Risk,” Dædalus 149

(2) (Spring 2020).

39 Anya Loukianova Fink and Olga Oliker, “Russia’s Nuclear Weapons in a Multipolar
World: Guarantors of Sovereignty, Great Power Status & More,” Dædalus 149 (2) (Spring
2020).

40 Li Bin, “The Revival of Nuclear Competition in an Altered Geopolitical Context: A Chinese

Perspective,” Dædalus 149 (2) (Spring 2020).

41 James M. Acton, “Cyber Warfare & Inadvertent Escalation,” Dædalus 149 (2) (Spring

2020).

42 Christopher F. Chyba, “New Technologies & Strategic Stability,” Dædalus 149 (2) (Spring

2020).

43 Linton F. Brooks, “The End of Arms Control?” Dædalus 149 (2) (Spring 2020).
44 Ibid.
45 James Timbie, “A Way Forward,” Dædalus 149 (2) (Spring 2020).
46 Nina Tannenwald, “Life beyond Arms Control: Moving toward a Global Regime of Nu-

clear Restraint & Responsibility,” Dædalus 149 (2) (Spring 2020).

47 “This Constitution, and the Laws of the United States which shall be made in Pursu-
ance thereof; and all Treaties made, or which shall be made, under the Authority of
the United States, shall be the supreme Law of the Land.” Constitution of the United
States of America, Article VI, https://www.archives.gov/founding-docs/constitution
-transcript#toc-article-vi-.

48 The U.S. Department of Defense has defined resilience as “The ability of an architecture
to support the functions necessary for mission success with higher probability, short-
er periods of reduced capability, and across a wider range of scenarios, conditions, and
threats, in spite of hostile action or adverse conditions.” A recent study suggests that
the resilience of potentially targeted systems can be improved in many ways, includ-
ing disaggregation, distribution, diversification, protection, proliferation, and decep-
tion. See Office of the Assistant Secretary of Defense for Homeland Defense & Global
Security, Space Domain Mission Assurance: A Resilience Taxonomy (Washington, D.C.: Office
of the Assistant Secretary of Defense for Homeland Defense & Global Security, 2015),
https://fas.org/man/eprint/resilience.pdf.

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149 (2) Spring 2020Christopher F. Chyba & Robert Legvold Conclusion: image

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