After two decades of stagnation in arms control, Russia and the United States have pledged their support for deep reductions in their nuclear forces. But this vision remains plagued by doubts—many hold on to the belief that, when it comes to deterrence, size matters. Will downsizing the number of nuclear arms threaten a country’s security?

In a new Adelphi book, Deterrence During Disarmament, Carnegie’s James Acton examines long-held concerns about the effectiveness of deterrence at low numbers, the possible incentives to use nuclear weapons first in a crisis, the potential for rearmament, and risks surrounding nuclear multipolarity. At an event hosted by Carnegie, Acton discussed the book with Andrew Parasiliti of the International Institute for Strategic Studies. Carnegie’s Toby Dalton moderated.

Disarmament and International Security

In his opening remarks, Parasiliti highlighted the relevance of disarmament to international security. Acton expanded on his comment, noting that any serious argument for deep reductions needs to consider their effects on international security. He also noted that any practical scheme for deep reductions must be both gradual and eventually multilateral.

Concerns About Reductions

Acton’s book surveys concerns about deep reductions based on both the deterrence literature and, more importantly, interviews with a wide array of former and current officials and experts. Beyond the fear of a step into the unknown – which Acton noted is not entirely fair, given instances during the Cold War where the antagonists had relatively small arsenals – four primary concerns motivate skepticism about arms reductions:

  • Central Deterrence: Central deterrence is the ability of a nuclear-armed state to deter aggression against itself. Various argument are put forward as to why effective deterrence requires large arsenals. The most important of these relates to the question of what adversaries value. Since the late 1970s, U.S. targeting strategy has been based partly on the premise that probable American adversaries do not value their citizens as much as their sources of state power (political leadership, industry, military forces, and command and control infrastructure). This assumption  results in plentiful targets and hence a need for many weapons.

    Given its Cold War roots, Acton argued that U.S. thinking needs to be re-evaluated in light of new evidence that suggests the United States developed an incorrect understanding of what the Soviet Union valued. Historical case studies including the Berlin Airlift – where a small number of nuclear weapons probably acted as a significant deterrent to Soviet escalation – add further credence to the case for the effectiveness of small arsenals.
  • Extended Deterrence: Extended deterrence is the ability of a nuclear-armed state to deter aggression against allies. The most important argument as to why large arsenals enhance extended deterrence relates to “damage limitation”: if the United States can destroy all or almost all of an adversary’s nuclear forces, then it can limit the damage it would suffer in a nuclear war and thus enhance the credibility of its threats. However, Acton observed that the historical evidence suggests that political leaders do not distinguish between outcomes in a nuclear war – they appear to view any nuclear exchange as devastating. Furthermore, the academic literature overstates the ease of destroying an enemy’s nuclear forces. If leaders do not distinguish between outcomes and the total destruction of an adversary’s forces is unachievable then maintaining a large arsenal for damage limitation adds little to extended deterrence.
  • Crisis Stability: Another justification for large arsenals is that they reduce the incentives to strike first during a crisis. The fear here is that as arsenals shrink, they grow less survivable, potentially creating incentives to use nuclear weapons out of the fear that an adversary might do so first. Acton argued that arsenal size is only one factor – and not even the most important – in enhancing survivability. Indeed, crisis instability might be a problem in future – even at high numbers. In consequence, arms control to enhance stability is a worthwhile activity regardless of whether the United States seeks deep reductions.
  • Rearmament Stability: The least discussed – but probably most problematic – aspect of deep reductions is the possibility of rearmament. In particular, with smaller arsenals, the possibility of a growing conventional imbalance sparking rearmament could grow. Acton identified three factors affecting the likelihood of rearmament: 1). Doctrine; 2). Conventional imbalances – weaker states use nuclear weapons to offset conventional imbalances; 3). Transparency of nuclear weapons production complexes.

He concluded by observing that while low numbers of nuclear weapons are not unconditionally stable, the right arms control measures during reductions  would enhance stability. He noted, however, that politically such measures might be very difficult to implement.