Elbridge Colby, the US undersecretary of defense for policy, wants to make American nuclear threats more credible to make nuclear war less likely. However, achieving the first objective may undermine the second.
In recent remarks to the US Strategic Command Deterrence Symposium, Colby outlined an emerging approach to deterrence built around providing the US president with credible and “rational” military options.
Colby’s core proposition is that deterrence is credible only when political leaders have a broad range of military options to respond to aggression without ever being forced to choose between accepting defeat and initiating catastrophic nuclear war.
Colby appears to be channeling the rationale that animated the Kennedy administration’s notion of “flexible response” and attempting to adapt it to the contemporary context.
The original “flexible response” emerged from a similar crisis of credibility. By the late 1950s, the Eisenhower administration’s doctrine of “massive retaliation” looked increasingly implausible as the Soviet Union acquired a survivable nuclear capability.
Would Washington really initiate general nuclear war in response to limited aggression? American responses to crises over Quemoy and Matsu in 1954 and 1955 and to the Soviet crushing of the Hungarian revolution in 1956 suggested not.
General Maxwell Taylor, who would go on to be an influential military adviser to President John F. Kennedy, famously argued that this left an American president choosing between “humiliation or general nuclear war.”
The Kennedy administration consequently sought military options appropriate to different levels of aggression to ensure, as President Kennedy put it, that it could be met with a response that was “suitable, selective, swift and effective.” The primary objective, then, was to reconcile deterrence credibility with escalation control.
Colby suggests that the US confronts much the same dilemma today. As he puts it, Washington needs “options” to “be able to defend the far-flung interests that the United States has in the world” without risking people “ducking under their school tables like it’s 1955.”
His emerging strategy has three components. First, strong conventional forces should deny adversaries the ability to achieve limited military objectives.
Second, credible limited nuclear options are necessary to prevent adversaries from exploiting the gap between conventional defeat and all-out nuclear war.
Third, allies in both Europe and the Indo-Pacific must shoulder more of the conventional burden, reducing the likelihood that Washington confronts an early choice between capitulation and nuclear escalation.
Colby argues that this is particularly relevant in the Indo-Pacific, where he analogizes American strategy to the Allies winning the Battle of Britain rather than “marching on Berlin.”
In a clear reference to a Taiwan scenario, Colby says that Washington’s objective is to “prevent anybody from crossing a body of water and sustaining operations in the face of determined resistance” rather than threatening the destruction of China itself.
Conventional denial, however, is the first step on the escalation ladder – one on which the US nuclear arsenal reinforces rather than substitutes for conventional deterrence.
Colby makes this explicit with reference to Europe, arguing that the “best thing” European allies “can do for nuclear deterrence” is “to invest in their conventional forces” as weakness here could create “conventional gaps that could be exploited” by adversary
“brinkmanship” to “put us in a very unfavorable position.”
Credible allied conventional forces, in combination with US “strategic” and “theater-level” capabilities, Colby maintains, would “provide a very effective deterrent.”
But for nuclear weapons to reinforce conventional deterrence, Colby argues, the US president must have “credible, rational nuclear options” including “counterforce” and “strategic counterforce options” designed to support “denial defense” and escalation management.
Colby argues that this is less about the “range of the weapons” within the US arsenal and “more about rationally employable, limited options that advantage us and stand the chance of favorably managing escalation and not getting us into an inexorable spiral” with an adversary.
This logic may be intuitively compelling, but it rests on the problematic assumption that escalation can be calibrated with sufficient precision.
Colby specifically points to Ukraine’s strikes deep inside Russia, including against strategic capabilities, as evidence that conflict can move high up the escalation ladder while remaining controlled.
Perhaps. More problematically, he appears to extend this understanding of escalation dynamics to a potential US-China conflict over Taiwan. Such a conflict, however, would be profoundly different to the Russia-Ukraine war, as it would involve not only different geography, interests and perceptions but also two sophisticated conventional and nuclear powers.
US reliance on counterforce options could make this especially dangerous. American strikes on Chinese missile forces, command systems, satellites, or mainland bases might appear limited and rational in Washington because they support conventional denial. Beijing, however, would likely interpret the same operations as preparation for a disarming attack on its nuclear deterrent.
Colby contends that such an outcome can be avoided by a “realistic attunement to the reactions not only of our allies and others but also to red” (i.e., adversary perceptions). But recognizing the security dilemma does not resolve it, particularly when Colby appears to believe that American nuclear strategy can be “cost-benefit rational” and proportionate.
However, as numerous studies have shown, nuclear crises are complicated by uncertainty, imperfect intelligence, organizational pressures, domestic politics and misperception. The notion that policymakers can “rationally” ascend and descend an escalation ladder, one carefully calibrated step at a time, is at best wishful thinking.
A further credibility problem remains – one that more nuclear options cannot solve. Colby argues that credible nuclear options should strengthen American extended deterrence. But this risks conflating the credibility of US capabilities with the credibility of its commitments.
Providing an American president more plausible ways to use nuclear weapons demonstrates that Washington can respond, but it does not necessarily mean that Tokyo, Seoul, Manila or Canberra will be convinced that the president will respond when doing so exposes American cities to nuclear retaliation.
Indeed, Colby himself emphasized in his remarks the need to ask whether something happening “halfway around the world” was in fact “worth it” for the US to justify action. That may be consistent with the administration’s proclaimed “America First” principles, but it will do little to dispel allied doubts about US security commitments.
Colby has identified a genuine problem. A nuclear guarantee that leaves a president choosing between surrender and Armageddon is not credible, and stronger allied conventional forces, backstopped by US nuclear capabilities, may be part of the solution.
Yet the danger in Colby’s construct lies in the apparent belief that making nuclear war more “limited” and controllable necessarily makes deterrence safer.
The more “usable” nuclear weapons become, the more credible American threats may appear – but adversaries, too, will take their use more seriously, potentially intensifying fears of counterforce attack, increasing pressures for pre-emption and blurring the boundary between conventional and nuclear war.
Dr Michael Clarke is an associate professor of international politics and strategy at the Deakin Center for Future Defense and National Security, Deakin University, Canberra, Australia and an adjunct associate professor at the Australia-China Relations Institute, University of Technology Sydney.
Clarke’s research focuses on Chinese politics, foreign policy and the PLA, American grand strategy, nuclear strategy and non-proliferation and Australian defense and strategic policy.
