Introduction

The world has entered a new nuclear era whose characteristics and challenges differ markedly from those of the Cold War. No longer dominated by only two nuclear superpowers (even if Russia and the United States still possess the lion's share of nuclear weapons), its dangers are at least as great as those during the Cold War, and made more so by a general unawareness of the multiplying ways a nuclear war could begin. Five nuclear-armed states – China, India, and Pakistan, in addition to Russia and the United States with its allies Britain and France – now set the contours of a multisided matrix, determine whether and when nuclear weapons will be used, and bear the responsibility for deciding whether and by what means the risk of nuclear war can be averted. Other states with nuclear weapons, such as North Korea, further complicate the picture by creating additional pathways to nuclear conflict and generating U.S. responses that stir Russian and Chinese opposition and counteractions. Israel's nuclear arsenal remains recessed and opaque. Beyond this changing geostrategic topography, advances in weapons technology and the opening of new frontiers, such as cyber capabilities and artificial intelligence, make a shifting environment still more complex.The collapse of the Soviet Union and, with it, the fading fear of nuclear war led to a general disregard of nuclear issues in key relationships, with the exception of the security of nuclear holdings in former Soviet Republics, including Russia. Nuclear states and their defense planners continued to tend to their nuclear forces while adjusting their role to a reality no longer centered on the prospect of a war between two nuclear hegemons. Aided by the arms control agreements between the superpowers in the last years of the Cold War and the first years after, and by the positive hopes for a new and constructive relationship between the United States and Russia, the world's nuclear states welcomed this less tense reality. Attention in the United States shifted to threats associated with the nuclear ambitions of countries like Iran and North Korea, and to the possibility of nuclear terrorism. True, by the turn of the century, Russia and China had begun to emphasize what each saw as elements of an ongoing U.S. nuclear threat, and the United States now included both in the scenarios guiding its efforts to refine its extended deterrence commitments in Europe and Asia. But this recrudescence of concern over nuclear trends largely flowed along channels of familiar thought rather than turning national attention to the formidable new challenges of a multipolar nuclear world.The evolution from what was fundamentally a two-sided order into today's more multifarious setting adds complexity and gives a new dimension to familiar challenges and dangers. We highlight five. Some changes are a matter of multiplication. Originally limited to the United States and the Soviet Union, competitive and potentially adversarial nuclear relationships have expanded to include India and Pakistan, the United States and China, India and China, and in the likely future, the United States and North Korea. In the twentieth century, the United States and Soviet Union developed elaborate triads of nuclear weapons on land, at sea, and in the air. Now, while the United States and Russia are modernizing and enhancing all three legs of their triads, three new countries – China, India, and Pakistan – are fashioning triads of their own. In several of these state pairings, the interactions are not simply bilateral, but are affected by actions directed at third parties. For instance, Pakistan interprets India's nuclear posture toward China as a message meant for itself. China's positioning toward the United States evokes India's apprehensions. When the United States deploys missile defense systems to offset a North Korean nuclear threat, China and Russia react to it as the camel's nose under a tent eventually designed for them. And the competition between offensive and defensive systems reopened between the United States and Russia by the resumption of efforts to develop ballistic missile defense systems is now mirrored by Chinese and Indian moves in the same direction.Second, technological advancement, a constant driver of change since the dawn of the nuclear age, plays an increasingly diverse and mixed role in today's nuclear setting. Technologies that, as advocates argue, offer more effective deterrence by increasing the usability and therefore the credibility of nuclear weapons, and increase the flexibility and confidence of those with their finger on the nuclear trigger also present novel complications. They raise concern over the survivability of nuclear forces, blur the line between conventional and nuclear war-fighting, risk transforming space warfare into an integral part of nuclear warfare, and, in a crisis, potentially decrease decision-making time. For instance, new conventionally armed hypersonic boost-glide and cruise missiles provide decision-makers with options for executing extended-range strategic strike missions short of nuclear use, but if they obscure from an opponent whether they are, in fact, nuclear-armed, they also threaten crisis stability. Smaller, lower-yield, and more-accurate nuclear warheads make the threat of their use more credible, but that is because they are also more usable, creating tension between effective deterrence and the risk of lowering the threshold to nuclear war. A variety of remote sensing technologies promise improved information for decision-making in a nuclear crisis and, perhaps, more effective defenses, but simultaneously may render even hard-to-locate mobile missile systems vulnerable to attack. And while emerging cyberspace surveillance capabilities may provide unparalleled real-time information about others' nuclear forces and activities, they may also accentuate others' sense of vulnerability to nuclear-, conventional-, or cyberattack.Third, concepts key to understanding the original Cold War nuclear era are either under stress or undergoing unpredictable change. Strategic deterrence and its nuclear component take on more complex colorations when nuclear and non-nuclear deterrence are integrated and the task – as has been acknowledged by both U.S. and Russian planners – is to transform nuclear and conventional weapons along with cyber and other hybrid tools into a “comprehensive deterrence” mosaic. Internal to the concept of nuclear deterrence, some countries are again focusing on “limited nuclear options” and thinking through their calibration, while others are struggling with whether their minimum deterrence postures need to be altered: either by developing counterforce options – that is, a capability and strategy for disarming the other side of its nuclear weapons – or by considering a “launch under attack” retaliatory option. Taken together, this whole array of challenges raises the question of whether there can be crisis stability in a cluttered, heterogenous nuclear environment and, if so, on what basis. Even the standard that came to underpin the notion of crisis stability in the U.S.-Soviet relationship-mutual assured destruction (mad) based on each side's ability to retaliate massively after a nuclear first strike – seems to some either too narrow or too imperiled.Fourth, the already-contested realm of nuclear norms – shared principles that shape or have potential in the future to shape the behavior of nuclear actors – is growing increasingly murky and unsettled. The “nuclear taboo” – that is, the questioned ethics of nuclear use – seems further weakened by the attention given to the development of weapons for limited, and therefore more plausible, nuclear use. Flatly rejected by the United States and Russia, the formal “no-first-use” nuclear doctrines of China and India waver as India identifies exceptions to its application and China weighs its feasibility in the face of threats it sees from the United States. Meanwhile, an international movement for a treaty banning nuclear weapons has gathered momentum among the majority of countries that do not have nuclear weapons, and its long-term effects in the parallel universe of public opinion is unclear.Finally, the dangers of the earlier nuclear era remain: some familiar, some in altered form, and to them are added new ones. The risk of inadvertent nuclear war remains, but now the pathways to it have multiplied across more regions and relationships. The Cold War potential for misreading the other side's nuclear thinking and plans swells when it extends to a larger and diverse set of nuclear actors. The accumulated conceptual refinement and residual understanding on nuclear issues built between the United States and the Soviet Union were the result of fifty years of strategic nuclear arms negotiations and dialogue; this shared understanding has no modern counterpart in any other bilateral or trilateral nuclear relationship. Further, the risk of nuclear conflagration during the Cold War – serious at key crisis moments – arose principally in a single relationship. It is now present in several.Particularly significant, the original Cold War nuclear competition was gradually moderated by progress in bilateral strategic nuclear arms control arrangements reached from 1969 to 2010. The new era has slowly dismantled this bilateral arms control framework, with no clear prospect that it will be revived and extended. Even more remote is the possibility that a framework or frameworks encompassing other, let alone all, nuclear powers can be achieved.The authors in this issue of Dœdalus – a mix of security scholars, physicists, statesmen, and political scientists – address these and other dimensions of this new multipolar nuclear era. Their analyses are sensitive to the challenges and potential dangers posed by a world with nine nuclear players, but also consider developments and measures within their respective spheres that could alter or mitigate these challenges and dangers. The result is not a comprehensive exploration of all facets of a changing nuclear environment. Not all nuclear relationships or the dynamics in all regions are addressed. Rather, the focus is on salient aspects of the change underway among the major nuclear powers, with a primary emphasis on the United States, Russia, and China. The intent is to capture the essential features of the nuclear world we have entered, and to stimulate among policy-makers and the engaged public a recognition of the challenges that it poses. Other dimensions, such as the effects of domestic politics on the choices countries are making, receive limited treatment.Integral to the creation of this issue of Dœdalus has been the collaboration among its authors. First in a planning session and then in an authors' review conference, they have been generous in responding to one another's work, raising questions, offering suggestions, and wrestling with areas of disagreement. We are confident they would agree that, as a result, the analyses and arguments the reader will encounter are sharper and more refined than when the exercise began. And the exercise broadly is one, we believe the authors would also agree, that policy-makers in the major nuclear powers, their expert communities, and engaged publics need to replicate.The analysis is divided into three parts. The essays in part one explore how an evolving world of multiple nuclear powers interacts within a larger international setting that, too, is in motion. A fractured and convulsive international environment now includes multiple tension-laden nuclear pairings, several of which are complicated by nuclear third parties. Steven Miller, in his essay “A Nuclear World Transformed: The Rise of Multilateral Disorder,” considers this altered landscape and assesses its larger implications. He notes that the former overarching bilateral nuclear relationship now coexists with a series of regional nuclear subsystems in South Asia, East Asia, and the Middle East, and ponders the consequences. He assesses what it means that this new, multidimensional nuclear order is “functionally unregulated,” that the gap between the core and lesser nuclear powers has effectively shrunk, and that the kaleidoscope has not stopped turning. It is a world, in which the key their nuclear thinking no longer to one but several nuclear in which the no longer between two but in a among even in which the of are no longer to the core but have into the new regional nuclear and in which the former and now bilateral arms control framework from the earlier era no longer and an remains this with this and both among and between is of the essays in this with more so than the three essays the and U.S. to the nuclear challenges these countries The authors differ and make an to one and in their essay Nuclear in a of focus on Russia as still one of the two key actors in this more complicated nuclear setting. from an of of the changing and its for national they turn their attention to the role Russian defense planners to nuclear their on how nuclear weapons into a framework of strategic their on evolving nuclear the first use of nuclear weapons, and limited nuclear the feasibility of and the of inadvertent nuclear war. this they to Russian on the nuclear and postures of the other key players, at the of which is the United States. Russian the U.S. Nuclear the of the threat they to nuclear and the U.S. technological advances that them are and They with about Russian on the or nuclear and Russian on and arms his take in of Nuclear in an A Chinese He his first on how U.S. and Russian positioning in the larger international setting has the two countries a U.S. and a Russian the gap between the United States and China that will the to major powers spheres of and the of the nuclear universe as a growing of states the nuclear this means for China his He a China whose and is growing along with the of its and security but that has the intent to either Russia or the United States as a nuclear and that is struggling to a nuclear that it measures to the posed by the United States. 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He these from a of the on strategic stability from the of and by the the on to with Russia and the arms tension this the to the nuclear by the of Russia and the United States in their to nuclear and, in the United States, the of political for the nuclear a to arms He attention on what the United States and Russia could take to mitigate the effects be into measures to and in the nuclear of the United States and Russia, areas of potential security that could the nuclear actions to the for bilateral to some of the and U.S. actions that can have an including in strategic at each some familiar but some to the nuclear and others designed for new In to inadvertent an in which arms control has made only limited in to be thought of not as an but as a means to an a this in his to the question that arms control can the of nuclear use, crisis and or nuclear control the and shape of nuclear arms and opening the to security in other his to several agreements reached between the United States and the Soviet Union during the Cold War. The a concept as the for strategic stability and a potentially and arms The Nuclear an of nuclear weapons that posed the threat of a to nuclear use because of the short they The would have the development of multiple the that in a crisis either side these would to or the for nuclear arms is about the of further or even nuclear arms control the the of a set of in of strategic the for nuclear arms control is in with of the on Russia, to both this of the analysis by the role that arms control during the Cold War nuclear era. He his on the tension between the of arms control by its original like and its to the and national security by political decision-makers at the time. He rather than to the of strategic stability based on forces, the arms control more on the of further nuclear powers and U.S. And then for largely political rather than strategic how it, in on on elements in each side's forces that strategic stability. by on the to which the for arms control and its future role in a multidimensional world of nuclear powers will the complex of narrow nuclear larger geostrategic and political the last the of the the authors turn to three dimensions of the posed by the multipolar The of technology remains a dimension of the the nuclear setting is than the technologies for which there is an on developing a framework for understanding the of new technologies on the concept of strategic stability. In his essay Technologies Strategic identifies several that determine how a new technology the and with which the technology – whether a weapons or an technology – among nuclear the capability of a technology and its for deterrence and and its on decision-making the of information in the as as the for and each or strategic on a of more to which each gives need to be in including from a a effects or differ from those of these then ways by which technological pathways of strategic stability can be and this framework on three new hypersonic weapons and artificial emerging is more salient than the of including the prospect of cyber warfare into the nuclear In his essay the that potential cyber threats to nuclear forces and their and systems new pathways that are from by other result from key between cyber capabilities and other a more ability to an nuclear forces and tools offer an means of an ability to what as are to and more to than by other And in between what may be offensive and what is simply is creating of responding to cyber as if it were an attack. He then a between cyber and or inadvertent result of or the one or the other could that cyber capabilities by their are more to or through measures than other with for how states could the emerging from cyber of the major trends in this new nuclear is the growing momentum the movement in of a treaty banning nuclear weapons, now to state and in their the The Nuclear this as a new dimension of efforts to to with the nuclear They the analysis in the of of norms that have in the of nuclear on use, and political They with an exploration of the of such their their potential and the they They the that each set of norms has had or could have on the behavior of nuclear by the of and for to them. They that norms do not alone but a of or the of the the is between that the of a and means that the of and after the potential of the on to consider what be to to nuclear dangers that would also the that states from the majority of with two authors with a future arms control and what could an increasingly multidimensional nuclear in “A the by setting what states could short of to the of their and to deterrence, and to the risk of conflict through and In the first increasing the of and surveillance and as as nuclear forces and their and control systems from the deterrence areas – for cyber threats and threats to space – in which is or The majority of his essay at a of measures along multiple dimensions that would and stability to an evolving and nuclear with a variety of and bilateral commitments strategic and nuclear forces, to and and with a array of measures to the associated with missile and conventional He that on such a of measures can be given a serious since it could address the of by the United States and Russia. are for improved of between nuclear a to longer and about the of new such as artificial intelligence, when to the nuclear and an emphasis on and to policy-makers for the complex that they will need to make essay toward a of Nuclear a to ways and means to nuclear dangers the of – formal or bilateral, or – in the of arms what norms be that nuclear-armed states toward a by the of nuclear and would be the same as that of arms to provide nuclear use, and nuclear could this be other than through in political and commitments between the Soviet Union and the United States. Some were simply parallel or others and still others of such as the Nuclear these a of along the same that are to a nuclear world that from its to that in the present political the by and will be essential if the more are to a the we from the major and highlight the made by the authors. We also areas of among them as as of in a last we from each in for the challenges of this complex and multipolar nuclear

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