The devastating large-scale armed conflict between Russia and NATO-backed Ukraine requires that policymakers consider how best to address the emerging strategic and operational challenges generated by great power competition. One fundamental question is, What should U.S. nuclear posture be to best deter competitors along the continuum of conflict?
This is particularly important to the Sea Services, both because the U.S. Navy is responsible for one-third of the U.S. nuclear triad, and because the competition between the United States and its primary competitor, China, has a distinctly maritime flavor. The most likely scenarios for armed conflict involve extensive naval operations as well as potential nuclear escalation. In addition, the Navy is uniquely suited to operationalize some of the most important aspects of the deterrence mission. Decision-makers must consider what constitutes the most effective nuclear strategy. Ultimately, the United States must focus nuclear deterrence operations on the high end of the conflict continuum and devote remaining resources to other methods to deter at lower levels.
What Is ‘Nuclear Posture’?
Nuclear posture is a state’s declaratory policy surrounding the purpose of its nuclear arsenal combined with matching force structures, material capabilities, and command and control structures in place for the nuclear forces.1 Because deterrence is about shaping the thinking of potential aggressors, what the United States says and what it does are both important to nuclear posture. In the past, the United States and other countries’ nuclear postures have been described variously as “mutually assured destruction,” “flexible response,” “assured second strike” or “assured retaliation,” “counterforce” or “a countervailing strategy,” and, recently, “complex nuclear deterrence.”2
Specific to regional nuclear powers (which include China, India, Pakistan, Israel, South Africa, and France), Vipin Narang, a professor of nuclear security at MIT, identifies three possible nuclear postures: “catalytic”; “assured retaliation”; and “asymmetric escalation.” Each of these describes a distinct approach to nuclear deterrence, with the asymmetric escalation model assessed to be the most effective at deterring aggression.3 Examples of current nuclear postures include China’s assured retaliation posture and Pakistan’s asymmetric escalation posture. Narang’s typology does not apply to the other nuclear-armed states (past or present) and work on specific categorizations of super-power nuclear postures is limited and highly subjective. No single list of nuclear posture options has been developed, mostly because great powers have the resources to pursue a much wider range of nuclear strategies than more resource-constrained countries.
Ultimately, a nuclear posture may be understood as the doctrine and operationalization of a state’s nuclear forces for the sake of deterring and potentially defeating adversaries if necessary. U.S. strategic guidance currently states the purpose of the country’s nuclear posture is to: deter strategic attacks; assure allies and partners; and allow the United States to achieve its objectives if deterrence fails. Furthermore, the 2022 Nuclear Posture Review Fact Sheet states that “the fundamental role of U.S. nuclear weapons is to deter nuclear attack on the United States, our allies, and partners.”
What It Takes to Deter
Two leading deterrence scholars, Alex George and Richard Smoke, define deterrence as “simply the persuasion of one’s opponent that the costs and/or risks of a given course of action he might take outweigh its benefits.”4 Deterrence, therefore, hinges on a rational process of calculating costs and benefits and will succeed when the opponent concludes that the considered activity will not be worth the effort. But what makes deterrence work? There is no consensus, but I suggest that deterrence is based on five unchanging principles.
First, nuclear deterrence partially hinges on the principle that the adversaries are (and perceive themselves to be) vulnerable to a punishment threatened if an adversary crosses specified red lines or menaces the vital interests of the state. Bernard Brodie, one of the first nuclear strategists, stresses that vulnerability is a key component of deterrence, and it was deemed necessary to “explore all conceivable situations where the aggressor’s fear of retaliation will be at a minimum and to seek to eliminate them.”5 Ken Waltz, a leading voice in deterrence theory has argued that vulnerability should cause states to be more cautious and to refrain from even lesser provocations because of the fear of escalation and because the gains can only be limited.6 Neither completely effective defense nor nuclear weapons abolition is possible, but only these could remove vulnerability in the nuclear era. Barring voluntary disarmament, there is no likely development in the near to medium term that might remove this sense of vulnerability from the minds of adversaries.
Second is the principle of uncertainty. Nuclear deterrence requires that, though the adversary knows of the existence and scale of the nuclear state’s weapons, it cannot know the exact extent or location of capabilities or when they might be employed. As Waltz writes, “In a nuclear world, a would-be attacker is deterred if it believes that the attacked may retaliate. Uncertainty of response, not certainty, is required for deterrence because, if retaliation occurs, one risks losing so much [italics added].”7
Of additional importance is uncertainty about the ability to control escalation. Since the severity of the consequences of nuclear war are so enormous, even a low probability of unintended escalation is enough to induce caution. As Schelling writes, “small wars embody the threat of a larger war; they are not just military engagements but ‘crisis diplomacy.’”8 For Schelling, the very essence of a crisis is its unpredictability and the fact that, once a crisis starts, there is no guarantee that either state can control its development.
Third, nuclear deterrence partially hinges on the exceptional nature of nuclear weapons. After more than 77 years of nuclear non-use, whether non-use is simply a “tradition” or has risen to the level of a full-blown “taboo,” nuclear weapons are considered something much more than merely another bomb.9 Herman Kahn wrote early on that “there is a genuine distinction between nuclear and chemical explosions. The fact that very low-yield nuclear weapons could be developed which would render this distinction fuzzy and vague does not change this.”10 More recently, former U.S. Secretary of Defense Jim Mattis stated, “Any nuclear weapon used any time is a strategic game changer.” This special status adds to their deterrent value and is one reason why nuclear weapons are desired even among states with massive conventional capabilities. If nuclear weapons were to be routinized or normalized—for example by the adoption of numerous limited nuclear capabilities or of doctrines of nuclear warfighting—efforts aimed at deterrence could have the perverse effect of lowering the threshold for nuclear use. Nuclear deterrence, then, hinges on reserving nuclear use for truly exceptional circumstances. Otherwise, even small and so-called limited nuclear use is by and large expected to lead to escalation and the risk of a massive nuclear exchange. Keeping nuclear weapons in a category all by themselves therefore contributes to both deterrence and escalation management.11
Fourth, nuclear deterrence hinges on the adversary being a rational actor. In its simplest sense, rationality requires that actors can identify their preferences and can judge for themselves the best way to achieve their goals. This is important to consider in assessing nuclear posture because the U.S. strategy must aim at manipulating the rational calculations of adversaries, which involves understanding how one’s own capabilities are perceived by the other. Well-known security dilemma dynamics can play a role in counterproductive deterrence strategies if U.S. efforts appear to adversaries as aggressive preparations for preventive or preemptive actions.
Last, nuclear deterrence requires the communication of credible deterrence threats. Adversaries must know that if they threaten U.S. interests, the U.S. will be willing and able to deny benefits and impose unacceptable costs. Credibility requires demonstrating nuclear capabilities and the will to use them. This includes adversary awareness of robust and redundant U.S. nuclear command, control, and communications (NC3) capabilities under any scenario. Communicating credible deterrence is an active process. It is more than the static equivalent of the scarecrow in a farmer’s field. It is rather more like an active farmer who patrols the field with his shotgun, firing it occasionally to ensure and demonstrate it works. The nuclear equivalent is the regular maintenance, training, and exercising of nuclear forces under realistic geostrategic circumstances. This is not to suggest nuclear demonstrations—only the exercising of the launch platforms and NC3 capabilities required to support them and the test launching of unarmed ballistic missiles. These measures will contribute to general deterrence while communicating more specific and situationally determined threats in crisis is required to achieve immediate deterrence during a crisis or confrontation.
The Limitations of Nuclear Deterrence
The United States must develop a nuclear posture that acknowledges the risk of nuclear war while being vigilant not to encourage nuclear proliferation. There is no nuclear posture the country can adopt that will convince other states to abandon their nuclear weapons.
Most likely—and perhaps even exclusively—nuclear deterrence operations are capable of deterring activities only at the higher end of the spectrum of conflict. Nuclear weapons may place an upper limit on escalation from lower-level activities, but they do not contribute directly to the deterrence of those activities in the first place. By themselves, nuclear weapons do not help deter activities such as cyberattacks, terrorism, limited territorial disputes, the provision of massive military aid to allies or partners, or other “hybrid” warfare techniques, for example, but they may contribute to how far these activities escalate.
Third, nuclear weapons are not useful to coerce or compel other states. “Coercion” includes what many refer to as coercive diplomacy, as well as the potential actual limited use of nuclear weapons.12 Nuclear weapons cannot and should not be relied on to enhance the coercive capabilities of the states who possess them (i.e., to blackmail adversaries). Instead, nuclear weapons are most effective when held in reserve as a defensive capability and for denying benefits and imposing costs on aggressors once deterrence has failed
Nuclear weapons, it was hoped, would discourage not only major wars between nuclear powers, but also even lesser provocations. The nuclear revolution has not played out this way.13 States continue to engage in high-intensity conflict despite the risks of nuclear war. Nuclear weapons do, however, contribute directly to two limited but critical things: deterring nuclear and other major strategic attacks on the U.S. and its formal allies; and deterring direct, major state-on-state war between nuclear powers.
With these deterrence principles in mind, and considering the limitations of nuclear deterrence, these are some recommendations for U.S. nuclear posture. First, the nuclear declaratory posture should focus on communicating U.S. capability and will to respond when vital interests are threatened. The bar for nuclear use should be high, but the promise if that bar is reached should be a definite and punishing response. Relying on limited nuclear options to deter lesser actions is counterproductive, and only invites the testing of U.S. resolve. It risks a state engaging in provocations under the assumption that if the U.S. does respond with nuclear weapons, the response will be small enough that the state can absorb the attack and still achieve its objectives.
The declaratory posture should remain ambiguous about specific conditions that would trigger nuclear use, and the policy should reserve the first-use right in the face of severe threats to the United States or its allies. At the same time, declaratory policy should be clear that the United States will respond if sufficiently threatened and that nuclear weapons may be used in that defensive response. On the flip side, the United States should assure the world that if adversaries refrain from aggressive behaviors, the United States and its partners will work in good faith to address security concerns on terms acceptable to both parties.
Second, the U.S. nuclear posture should continue to be flexible. U.S. nuclear forces should be designed in such a way that any feasible target within an adversary nuclear state may be threatened at any time, and adversaries must know that this is the case. Flexibility relies on the survivability, reliability, and deliverability of each leg of the triad. This flexibility is not about tactical/warfighting nuclear capabilities, but rather about building devastating nuclear capabilities that may be launched from a variety of platforms and locations and will be sure to reach their targets. Toward this end, the Navy must maintain its dominance in survivable ballistic-missile submarines and should consider investing in a new sea-launched nuclear cruise missile (SLCM). This SLCM should not be considered a tactical capability, but rather a flexible delivery platform for strategic defensive weapons. In addition, the air leg of the triad should invest in improved delivery methods and pursue a more survivable nuclear posture by diversifying basing and engaging in deception operations to complicate adversary intelligence operations. Last, land-based capabilities should consider increasing exercises and incorporating mobile capabilities or rotating missile locations in fixed silos before and during crises to complicate adversary targeting. Most important, the United States must continue to invest in survivable NC3.
Third, with the demise of the Intermediate-Range Nuclear Forces (INF) Treaty, the United States should consider fielding a numerically modest mobile, land-based, intermediate or medium-range nuclear system. Again, this is specifically not about warfighting or tactical nuclear weapons, but rather about increasing the vulnerability and risk to adversaries if they threaten U.S. interests. Not only would these capabilities be able to be positioned in various locations around the world, but they may also be valuable tools to trade in future arms control negotiations.
Fourth, U.S. nuclear posture should be expressly against, both in declaratory and operational terms, the consideration of nuclear weapons as warfighting tools, or even worse, as deescalatory devices. Nuclear weapons employment is not a means to deescalate a conflict. While the United States warns Russia of its misguided thoughts in this realm, many in the U.S. strategic community, both past and present, have wrongly considered the limited use of nuclear weapons as a potentially effective signal to terminate a conflict. Part of this focus should be to maintain a firm stance on nuclear nonproliferation.
It is possible these measures to enhance flexibility may result in a nuclear arms race or proliferation. But the United States could mitigate this risk by the proper messaging regarding these new capabilities (as defensive, strategic weapons) as well as by limiting the number of such capabilities. Nonproliferation should remain a key aspect of U.S. grand strategy.
Finally, focusing nuclear deterrence on the high end of the continuum of conflict should encourage investment in other methods of deterrence at the lower end. This is directly aligned with the DoD concept of Integrated Deterrence. Threatening nuclear retaliation to lesser provocations is not credible. Instead, approaches based on the concept of deterrence by denial should be pursued. For example, in the case of highly destructive cyberattacks or attacks on NC3 systems, investing in protecting networks, identifying threats, and sharing data and intelligence with partners will be more effective in deterring adversaries. If the United States relies too much on nuclear deterrence it risks not investing enough in capabilities needed to deter other threats.
Nuclear deterrence is not full-spectrum deterrence on the cheap, but rather existential and high-end deterrence at a relatively high cost. Though its role is limited in scope, it is imperative and worth the required investments. The United States acknowledges and embraces the limits of nuclear deterrence by adopting a posture focused specifically on deterring major strategic and nuclear attacks and then devoting remaining resources to other key elements of national defense. Integrated deterrence requires that the United States invest in the right capabilities directed toward the correct threats. Nuclear weapons remain the backstop to controlling escalation and will continue to provide the baseline of U.S. strategic deterrence. If done correctly, nuclear deterrence can help ensure that strategic competition remains confined to the lower end of the continuum of conflict.
1. See: Vipin Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict, (Princeton NJ: Princeton University Press, 2014), 2–4.
2. For perhaps the best starting point to understand changes in nuclear strategy over time, see: L. Freedman, The evolution of nuclear strategy 3rd ed. (Houndmills, Basingstoke, Hampshire, Palgrave Macmillan, 2003).
3. Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict, 7.
4. A. L. George and R. Smoke, Deterrence in American foreign policy: theory and practice, (New York: Columbia University Press, 1974).
5. Bernard Brodie et al., The Absolute Weapon: Atomic Power and World Order 1st ed (New York: Harcourt, Brace and Company, 1946).
6. S. D. Sagan and K. Waltz, The Spread of Nuclear Weapons: an Enduring Debate 3rd ed. (New York: W.W. Norton & Co, 2013).
7. Sagan and Waltz, The Spread of Nuclear Weapons.
8. T. C. Schelling, Arms and Influence (New Haven, CT: Yale University Press, 1966).
9. T. V. Paul, The Tradition of Non-Use of Nuclear Weapons (Redwood City, CA: Stanford University Press, 2009); and N. Tannenwald, The Nuclear Taboo: The United States and The Non-use of Nuclear Weapons Since 1945 (Cambridge, UK: Cambridge University Press, 2007).
10. H. Kahn, On Thermonuclear War 2d ed. (Princeton, N.J: Princeton University Press, 1961), 540–41.
11. Daniel R. Post, “Escalation and Coercion: Exploring ‘Escalate to De-escalate’ Strategies in Past Wargames and Crisis Simulations,” Working Paper (Dissertation, Brown University, 2022).
12. T. S. Sechser and M. Fuhrmann, M. (2017) Nuclear Weapons and Coercive Diplomacy (Cambridge, UK: Cambridge University Press, 2017).
13. For one explanation for this see: Green, B. Rittenhouse. (2020). The revolution that failed: nuclear competition, arms control, and the Cold War. Cambridge: Cambridge University Press.