Public debate on nuclear deterrence often descends into acrimony, with accusations of naïveté and warmongering hurled around like casual insults. These polarised perspectives – rooted in misconceptions – hinder constructive dialogue and impede the pursuit of common ground which is at the heart of sound policymaking. Yet, whether arguing for deterrence or disarmament, both sides ultimately share the same overarching objective: the prevention of nuclear war.

The current unproductive discourse on nuclear deterrence stems from a fundamental misunderstanding of the concept itself. While some view deterrence as an ironclad guarantee of peace, others decry it as a reckless gamble. The reality is far more complex and elusive. Deterrence is undergirded by complex mechanisms, and a delicate balance between capabilities, credibility, and communication. To move beyond this impasse and ensure the continued effectiveness of deterrence, it is important to examine the factors that contributed to its success during the Cold War – recognising that the efficacy of deterrence is inherently difficult to prove – and adapt those lessons to the complexities of today’s security environment. Rather than reinventing the wheel, strategic investments should be made in modernising, diversifying, and strengthening the resilience of existing deterrent forces, ensuring their continued credibility in this new era of heightened nuclear risk.

Nuclear deterrence is not an immutable law of physics; it is a dynamic concept that can be challenged, adapted, and debated. While its effectiveness might be immeasurable, the reality is that it remains a powerful, psychological tool that has worked thus far, and for which no better alternatives are readily available. Indeed, deterrence is essentially a form of communication – a strategic dialogue conducted in the language of power. The continued investment and expansion of nuclear capabilities by adversaries to the western alliance demonstrate their recognition of the enduring power of this language.

The most important event of the Cold War was one that did not occur – thermonuclear war. This success is generally attributed to nuclear deterrence, or the manipulation of an adversary’s estimation of the cost/benefit calculation for taking a given action. In Austin Long’s words, deterrence is the generation of fear. The question of what made deterrence work in the Cold War has pitted scholars against each other for decades. On the one hand, advocates of the ‘nuclear revolution’ contend that the long peace is best explained by the non-usability of nuclear weapons and thus, crisis resolution hinged on a balance of resolve. On the other hand, some analysts argue that nuclear superiority underpinned deterrence. But deterrence in the Cold War was not just predicated on resolve or the military balance. Rather, deterrence was bolstered by a unique set of circumstances, such as an international system characterised by bipolarity, and a rational leadership that understood escalation risks and mutually feared warfare writ large.

Idiosyncrasies of the Cold War aside, luck also played an understated role in the deterrence equation. Near-miss nuclear accidents, close calls, and moments of brinksmanship are testimony to this. Decades later, Secretary of Defense Robert McNamara reflected: ‘And we lucked out. It was luck that prevented nuclear war.’

The concept of the ‘nuclear revolution’ was first articulated by Bernard Brodie in 1946. This term refers to the belief that the mutual vulnerability created by the existence of nuclear weapons engendered a fundamental shift in warfare, and even statecraft itself. As Brodie stated in The Absolute Weapon: ‘Thus far the chief purpose of our military establishment has been to win wars. From now on its chief purpose must be to avert them.’ Nuclear strategists such as Robert Jervis, Thomas Schelling, and Kenneth Waltz further developed this idea. They argued that nuclear weapons minimised, or even eliminated, the security dilemma that drives distrust between states. Further, if a state possessed a second-strike capability, its security was essentially guaranteed, even if the adversary had a bigger arsenal. According to these scholars, because a crisis could escalate inadvertently, both sides would have to behave cautiously, regardless of the military balance. ‘Many prenuclear ideas are now inappropriate,’ Jervis argued. For example, ‘Military advantage loses most of its traditional meaning.’ In the world of mutual assured destruction, nuclear superiority was deemed a meaningless concept, since both sides could manipulate the level of risk.

In contrast, some analysts contend that nuclear superiority was decisive, particularly in circumstances where a state is trying to extend deterrence. This logic fuelled much of the military investment throughout the Cold War. Conventional wisdom, eloquently expressed in many of the scholarly writings on deterrence, assumed that Soviet aggression would wax and wane as a function of Soviet perceptions of US military capability and resolve. For nearly four decades, Soviet and American leaders worried about the political and military consequences of strategic inferiority. These fears, combined with the worst-case analysis each side used to estimate the other’s strategic capabilities, drove an increasingly expensive arms race.

In the late 1940s, in the aftermath of Hiroshima and Nagasaki, the Soviet Union made an intensive effort to develop its own nuclear arsenal. In the early 1950s both sides developed thermonuclear weapons. Following the success of Sputnik in 1957, the United States accelerated its commitment to develop and deploy ICBMs. President Kennedy’s decision to expand the scope of the American strategic build-up in the spring of 1961 triggered a reciprocal Soviet decision. The Reagan build-up of the 1980s was a response to Brezhnev’s intensive spending in the previous decade and mounting concern that it had bought the Soviet Union a strategic advantage. But was this relentless fear of strategic inferiority solely responsible for upholding deterrence?

In accounting for deterrence success during the Cold War, the unique international system of the time, bipolarity, may have played a role. The Soviet Union and the United States were the only global superpowers, and a system dominated by only two, roughly balanced powers, is considered more stable.

Further, a crucial contributing factor to deterrence during the Cold War was rational leadership, which appreciated risks and mutually feared nuclear war. It was not merely the balance or perceptions of it that mattered; rather, it was the judgments leaders made about its significance. Understanding an adversary’s intentions was far more important than assessing relative capabilities.

Consider the Cuban Missile Crisis: Kennedy was uncertain whether overwhelming American strategic superiority would deter the Soviet Union. Khrushchev, however, was confident in the Soviet arsenal’s deterrent power, despite its smaller size. During the crisis, leaders focused on political pressures rather than the military balance, as evidenced in EXCOMM meeting transcripts. This success in resolving the crisis increased their confidence that the other shared their horror of war.

Nuclear deterrence in the Cold War worked when leaders on both sides feared war and were cognisant of each other’s fears. The Cuban Missile Crisis was a critical juncture for this reason because it persuaded Kennedy and Khrushchev, and some of their most important advisers, that their adversary was as committed as they were to avoid nuclear war. This mutually acknowledged fear of war made the other side’s nuclear capabilities less threatening and paved the way for preliminary arms control agreements.

With hindsight, it can be argued that neither Washington nor Moscow was ever so discontent with the status quo that it was tempted to go to war to force change. Instead, both countries ventured to make gains where there appeared little risk and continued to focus energies on vital interests. Without a compelling motive, leaders did not want to be culpable for the responsibility of war, even if the outcome might have been favorable to them. For instance, in the late 1950s and early 1960s, even when the United States could have launched a pre-emptive strike against the Soviet Union, American leaders hardly considered the option. The relative satisfaction that leaders possessed with the status quo and its preservation was an important reason that deterrence worked.

Finally, there are those who argue that deterrence was upheld through sheer luck. Analysts point to the dangerous crises, the near misses, the accidents, and even the Schelling-esque competitions in risk-taking that almost led to nuclear use in the Cold War. Luck, in this context, would mean the exact opposite of control. The mixture of human fallibility and nuclear technological complexity could have very well led to disaster. There were moments, including during Nixon’s nuclear alert in 1969, when civil-military relations and frustrations could have resulted in deeper fissures and mismanagement.

The implications for modern-day deterrence are profound. In a security environment characterised by multiple nuclear challengers, NATO decision makers may face not just inadvertent, but deliberate escalation and nuclear blackmail. To address these threats effectively, they must ensure the safety, security, and readiness of the nuclear arsenal, while also establishing clear escalation thresholds and red lines.

Moreover, in the years ahead, NATO must navigate a delicate balance between clarifying escalation thresholds, demonstrating resolve, and maintaining credibility in crises under a nuclear shadow. This will be a formidable challenge. How will we ensure that our luck does not run out? By preparing rigorously – this is at the heart of nuclear deterrence.

Leadership plays a pivotal role. Different presidents and advisors may interpret the same constellation of threats, arsenal characteristics, and doctrines in varying ways. Therefore, leaders must possess a deep understanding of nuclear escalation, risks, and adversarial intentions. In a future conflict with an adversary whose intentions are uncertain, deterrence stands at greater risk of failure. Intelligence collection should prioritise understanding an adversary’s values to identify values, vulnerabilities, comparative advantages, and leverage points.

Further, nuclear deterrence is not a static concept, but a dynamic one that demands constant adaptation to new geo-strategic realities and technological advancements. Failing to modernise undermines the credibility of threats, rendering them hollow. While historically, enhancing deterrence might have been visualised as simply sharpening swords, in the nuclear age it necessitates a multifaceted approach encompassing capability, credibility, and communication.

The evolving threat environment, characterised by multiple, revisionist nuclear powers with diverse capabilities, values, and decision-making styles, demands a more flexible nuclear posture and robust command and control. A wider spectrum of response options is necessary to ensure deterrence remains credible across a range of potential scenarios. Modernisation, diversified delivery systems, and resilient command and control enhance both capability and credibility. Deterrence requires more than just powerful weapons, however – it also necessitates clear communication, or establishing clear ‘red lines’ and ensuring adversaries understand the consequences of crossing them. As Michael Quinlan writes:

Effective deterrence has two main components, not just one. It undoubtedly requires that the adversary perceive the existence of capability, and of general will to use it if necessary, to exact in one form or another costs that he would find unacceptable. But it also requires that he have a sufficiently clear understanding of what is the action from which he must refrain.

Investing in pre-crisis capabilities planning and messaging – often misconstrued as ‘nuclear warfighting’ – actually demonstrates a deeper understanding of deterrence requirements. Herman Kahn aptly captures this logic:

Our attitude should be the same as an engineer’s when he puts up a structure designed to last twenty years or so. He does not ask, ‘Will it stand up on a pleasant June day?’ He asks how it performs under stress, under hurricane, earthquake, snow load, fire, flood, thieves, fools and vandals…Deterrence is at least as important as a building, and we should have the same attitude toward our deterrent systems. We may not be able to predict the loads it will have to carry, but we are certain there will be loads of unexpected or implausible severity

Kahn’s analogy underscores a critical aspect of deterrence: planning cannot assume a predictable and rational adversary. It must account for irrational actors, unexpected crises, and the complex dynamics of escalation. By anticipating the vast permutations of contingencies, we can strengthen our deterrent posture and reduce the likelihood of adversaries exploiting perceived weaknesses. Preparing for multiple scenarios is not about seeking war, but about enhancing deterrence to prevent it altogether. Lest we forget, war is the failure of deterrence.

In sum, nuclear deterrence is neither a magic bullet nor an obsolete relic. It is a complex and dynamic tool that demands continuous adaptation, clear-eyed assessment, and a nuanced understanding of its inherent risks. The success of deterrence during the Cold War was not solely attributable to any single factor, but rather a confluence of circumstances: bipolarity, rational leadership, and even a degree of luck. As we navigate a ‘new nuclear age’, we must learn from the past while adapting to the present.

This requires a multifaceted approach. We must invest in the modernisation and diversification of our nuclear capabilities, ensuring their resilience and credibility, but always with a focus on strategic necessity rather than simply matching our adversaries. Modernisation should be driven by strategic deterrence requirements and the assurance of our allies, not by a desire to showcase resolve or engage in a costly arms race. Furthermore, we must foster wise leadership that understands the delicate balance of escalation and restraint, the interplay between deterrence and arms control, and the ability to navigate crises and communicate effectively in the language of power. Crucially, we must cultivate a deeper understanding of deterrence across all levels of society, rejecting simplistic narratives and embracing the nuanced realities of this complex challenge.

The stakes are far too high to allow misconceptions to derail our pursuit of effective deterrence. By raising our collective ‘nuclear deterrence IQ’, we can foster a more informed debate, leading to sound policymaking and a greater chance of preventing the catastrophe that nuclear weapons represent. Ultimately, the future of humanity hinges not on blind faith in deterrence, but on our collective will to understand its complexities, adapt to evolving challenges, and actively choose a path towards a safer world.