Research Brief

The United States, in pursuing its interests over the next decade, may well come into conflict with regional adversaries armed with nuclear weapons. How best to deter nuclear threats by regional states is, thus, an important question for U.S. national security strategy. In a recent RAND report, Nuclear Deterrence in a Regional Context, Dean Wilkening and Kenneth Watman outline an approach to answering this question.

Conceptual Framework

Nuclear confrontations between the United States and nuclear-armed regional adversaries will be games of brinkmanship, i.e., a competition in risk-taking where threats to cross the nuclear brink are made for strategic objectives. The outcomes of such interactions will be determined by the risk-taking propensities of each side and by the credibility of the opponent's threat to cross the nuclear threshold first, the likely consequences of the threatened attack, and the credibility and severity of U.S. retaliatory threats. Credibility, in turn, depends on perceptions of each side's resolve and capability.

This makes it clear why the United States may find regional nuclear deterrence difficult. In general, regional adversaries may be willing to take greater risks than the typically risk-averse United States. In addition, they may show greater resolve because regional conflicts affect their interests more directly than those of the United States.

The requirements for credibility also suggest an approach to U.S. regional nuclear deterrence. First, the United States should increase the perception of U.S. resolve through traditional diplomatic and military activities, e.g., by extending security commitments to regional allies and stationing U.S. troops overseas early in a crisis. Second, the United States should emphasize its military capabilities to impress upon nuclear-armed adversaries that the United States can do what it says it will do. Given perennial uncertainties about U.S. resolve, military capabilities are likely to be the more important dimension of U.S. regional nuclear deterrence strategy.

Deterrence Strategies

The effectiveness of U.S. deterrence strategy will depend on the objective the adversary's threat is intended to accomplish. Probable objectives include

  • deterring U.S. intervention in a regional conflict
  • intimidating or coercing other regional states, especially U.S. allies
  • preventing the total defeat of the state or regime by external forces.

To deter U.S. intervention, regional adversaries will try to convince U.S. leaders that the costs of intervention will be too high, given the U.S. interests at stake. The specter of high casualties, for example, could be raised by threatening nuclear attacks on U.S. troop concentrations, airfields, ports of debarkation and, perhaps, high-value targets in the U.S. homeland. Such threats ought to be relatively easy to deter because U.S. interests will be directly engaged and because the United States possesses overwhelming capability to retaliate in kind. The United States clearly has an overwhelming advantage with nuclear weapons and possibly also with conventional weapons. However, overwhelming conventional force may not be available early in a crisis and may not be sufficiently threatening to an adversary already facing conventional U.S. military action. To the extent that U.S. leaders are still concerned that deterrence might fail, the United States will need to develop active and passive defenses, as well as options to attack the opponent's nuclear capability before it can be used (i.e., preemptive and second-strike counterforce capabilities).

When an adversary's nuclear threat is intended to intimidate U.S. allies (e.g., to coerce allies into denying U.S. overflights or basing, or to create fissures within a U.S.-led coalition), the United States can extend deterrence to its allies by threatening severe retaliation, again stressing its ability to escalate the conflict to levels the opponent cannot match. Extended deterrence will be particularly credible if the U.S. homeland is invulnerable to nuclear reprisal. Ensuring invulnerability will require thin U.S. nationwide defenses against air, ballistic missile, and nontraditional delivery methods (e.g., a bomb in the hold of a merchant ship). To reassure U.S. allies that their homelands are also relatively invulnerable, the United States will need to deploy effective theater defenses.

Deterrence will be most difficult when a regional adversary threatens nuclear use to prevent the total defeat of its state or regime during a conventional war. Under these circumstances, an adversary's threat to use nuclear weapons will be credible because the adversary will have little to lose. The United States has two options for coping with such a threat. The first is to avoid placing the adversary in this situation, for example by stressing that U.S. aims are limited. However, this approach would encourage regional states to acquire nuclear weapons because it suggests that the possession of such weapons will guarantee the regime's survival in a future conflict with the United States. The second approach is to build up U.S. defenses and counterforce capabilities, because retaliatory threats alone are unlikely to be effective in deterring the opponent's threat to cross the nuclear threshold under these circumstances.

In summary, U.S. regional nuclear deterrence strategy relies on three capabilities: retaliatory options (nuclear and conventional), active and passive defenses, and counterforce. While all three may be desirable, the emphasis on each differs with the objective of the opponent's threat. To deter nuclear threats aimed at discouraging U.S. intervention or intimidating U.S. allies, U.S. strategy should emphasize retaliatory options. U.S. defenses and counterforce capabilities will increase the credibility of U.S. retaliatory threats under these circumstances, especially for extended deterrence, as well as providing some reassurance in the event deterrence fails. On the other hand, if the adversary threatens nuclear use to ensure its survival, then deterrence is apt to fail if the United States presses for the opponent's total defeat in the context of an ongoing conventional war. In this case, U.S. strategy should emphasize highly effective defenses and counterforce capabilities, since retaliatory threats alone may have little effect.

Implications for Proliferation

A successful U.S. deterrence strategy may also help discourage nuclear proliferation. If the United States acquires all three military capabilities, i.e., robust retaliatory capabilities (which it already has in its nuclear arsenal), active and passive defenses (some of which are currently or readily available), and counterforce capabilities, especially conventional counterforce (which is not currently available), the political and military utility of a regional adversary's nuclear arsenal would be substantially reduced. Conventional counterforce capabilities that focus on the early destruction of an adversary's nuclear arsenal, for example, may convince regional leaders that nuclear weapons will become lightning rods for preemptive U.S. strikes rather than means to enhance their security.

If, however, these capabilities are deemed too difficult or expensive to achieve, regional adversaries will have an incentive to acquire nuclear weapons, especially to ensure the survival of their regimes against external threats. Failure to construct an adequate U.S. deterrence strategy would leave diplomacy as the only tool for preventing the spread of nuclear weapons. If nonproliferation efforts fail, as seems likely given recent experiences with Iraq and North Korea, and the United States is unable to provide effective deterrence, then it must learn to live in a world with more nuclear powers, albeit small ones, and must adjust its foreign policy so that regional involvements occur only when the most important U.S. interests are at stake.

This report is part of the RAND research brief series. RAND research briefs present policy-oriented summaries of individual published, peer-reviewed documents or of a body of published work.

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