Bruno Tertrais explains the historical and political implications of nuclear deterrence. In his view, the possession of atomic weapons has indeed played a role in preserving peace.

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After numerous works on nuclear policy, Bruno Tertrais, Deputy Director of the Fondation pour la Recherche Stratégique, offers a synthesis in which he summarizes the issues, methods, discourses and scenarios for using the atomic bomb.

In doing so, the author comments on and discusses a literature that is little known in France, whether by academics or former political or military leaders. In ten tightly-packed chapters, he examines a number of questions: why have nine states acquired this weapon? what types of planning and discourse frame it? how do these states interact (including through threats)? Many of the concepts commonly used in this field are explained, as are the various historical interpretations and their respective arguments.

The author points out, however, that the question of whether deterrence "works" is in itself ambiguous: when an event doesn't take place, we can't say with certainty why it did not happen. For some observers, the almost eighty-year period of peace between the great powers since 1945 has been made possible above all by economic interdependence; others relativize the exceptionality of this period on a historical scale.

The functions of nuclear weapons

Nuclear weapons are supposed to protect countries from "existential risks". But the strategic reasons that drive a state to acquire nuclear weapons are varied. It may be when a state feels militarily weak in the face of an adversary (what General Pierre Marie Gallois calls "the equalizing power of the atom"). Or a country may initiate a nuclear program in order to gain greater international status, as was the case for France and India. Finally, a "pariah state" may seek to make its soil and regime safe from attack, or use the nuclear argument to negotiate with its adversaries, as Iran has done. In most cases, however, these countries proclaim that they will not be the first to use nuclear weapons.

Furthermore, not all countries possessing atomic weapons have the same threshold for use. This depends in particular on the size of their territory and its capacity to absorb (or not) an initial shock before considering a response, but also on the presence of conventional armies of varying strength.

On the other hand, 191 countries have signed the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). There are also good security reasons for giving up this weapon: obtaining it would encourage neighbors and/or rivals to do the same.

But in addition to the moral stakes, there are also political and reputational ones. For example, one of the reasons why American leaders decided not to use this weapon in the 1950s, during the Korean War, was that they did not want to be the ones to initiate a nuclear bombardment again, especially in Asia.

Moreover, one of the mainstays of nuclear policy is extended deterrence, and in particular the deployment of the American umbrella over its allies. But the credibility of such a commitment has been debated since the Cold War: would a territory on the other side of the Atlantic risk its own destruction to protect Poland, for example? According to Bruno Tertrais, the question is not so much whether the Americans are really prepared to do this: it's what the other side believes that matters.

The reliability of deterrence therefore depends on regular, consistent declarations, but also on the presence of military bases in the countries concerned, sometimes with on-site nuclear stockpiles. Beyond the rivalries between the great power, the umbrella probably prevents proliferation insofar as, without this extended and credible deterrent, many countries would start an acquisition program.

The principles of deterrence

The aim of deterrence is above all to convince the other person to abstain. In other words, it's not the sender of the message who decides whether it works, but the receiver. This principle of deterrence already existed in economic and/or military forms (sanctions, naval blockades, etc.) before being systematized for nuclear weapons. In each case, there are numerous examples of the failure of this strategy. Nuclear deterrence relies on a permanent dialogue between nations, and is therefore not sufficient to prevent any possible recourse to the bomb.

To be effective, the nuclear threat must be both credible and vague: credible from the point of view of the operational capacity of the state concerned to strike its target, without the missile running the risk of being intercepted, for example; vague because, despite the threatening formulas (the "incalculable", "unprecedented" consequences of such recourse are emphasized), the red lines must never be clearly stated, so that uncertainty about the consequences blurs the calculation of costs and benefits, and thus encourages the adversary to restrain.

Faced with this threat, the latter knows that he can either act below the stated conditions without being worried, or take the plunge and challenge the other's credibility in the process. In this situation, vagueness ensures freedom of action if the adversary is more adventurous than expected.

However, it should be noted that fear is not based solely on cold, rational calculation. First of all, it is often the criterion of irrationality that is brandished to accompany the threat and produce dissuasive effects: this is the "madman theory" employed by Richard Nixon in his day to try to put an end to the Vietnam War   and used more recently by Donald Trump to deal with North Korea.

Moreover, rather than being based on rationality, deterrence relies to a large extent on the imaginary, insofar as there is no precedent for it: Hiroshima and Nagasaki were bombed without any fear of retaliation. What's more, this imagination is fuelled by the technical evolution of weapons. While today's bombs are much more powerful than those of 1945 (because they are thermonuclear) and faster (thanks to ballistic missiles), they are less powerful than during the Cold War: their targeting is more precise, and their energy has been reduced.

This in no way diminishes the threat they pose: according to some analysts, producing relatively weak weapons would increase the risks of their use (what Bruno Tertrais calls the "temptation to use"); for others, this rule is hardly applicable to atomic bombs, which remain out of all proportion to conventional bombs, however powerful. In any case, since actual tests of these weapons are only carried out by computer modelling, we cannot pretend to know the exact effects of today's weapons, or the scale of the reaction.

Generally speaking, these are doctrines and discourses, and it is quite conceivable that actors will behave differently in the face of a growing threat. As the author writes, "nobody knows how a nuclear conflict would develop, but anticipations – acting on the basis of a hypothetical future action by the adversary – would play a major role in the dynamics of escalation".

For budgetary reasons, many missiles and bombers are dual systems capable of carrying both conventional and nuclear bombs. Intelligence and verification procedures therefore play a key role in interpreting enemy behavior. In the 1980s, for example, both the Soviets and the Americans thought they had detected a massive attack, only to discover incidents in their computers a few minutes later.

The effectiveness of deterrence

According to Bruno Tertrais, there are a number of indications of the effectiveness of nuclear deterrence, which can be explained neither by the argument of the economic interdependence of the great powers (which was not the case for the USA and the USSR during the Cold War) nor by the culturalist explanation of "war fatigue" after 1945 (which did not prevent nuclear-armed countries from fighting by other means, in the conflicts of decolonization, Korea, Vietnam, etc.), nor was it due to luck.

The acquisition of the atomic bomb has significantly reduced confrontations between countries that were previously engaged in open warfare, as in the case of India and Pakistan. Furthermore, nuclear-armed countries have regularly allowed themselves to invade a non-nuclear state (Grenada, Iraq, Hungary, Czechoslovakia, Lebanon, Ukraine...), but without suffering any themselves (with the exception of Israel in 1973, although Egypt planned to retake only the Sinai occupied since 1967, or the Falklands in 1982, when Argentina took advantage of the fact that the archipelago was far from the UK). Finally, North Korea only invaded the South before the latter came under the American umbrella.

Based on the testimonies of former officials, Bruno Tertrais lists eighteen key moments (diplomatic crises, wars, military exercises, computer errors) when nuclear use could have occurred. He is skeptical about the idea that we would have been on the brink of catastrophe, because the option was never actually considered, or even consciously rejected, by politicians or the military. The fact remains, however, that if war had indeed been declared at the time of the Blocs, escalation would undoubtedly have been swift.

Despite these optimistic findings on the effectiveness of nuclear deterrence, the author warns against a number of hasty judgments. In particular, he moderates the importance of rationality in decision-making, which is supposed to prevent anyone from going all the way and acting against their own interests: not only can actors be mistaken about the intentions of others, but they also tend to select relevant information based on prior choices.

Bruno Tertrais also highlights the importance of certain cultural, religious or ideological factors: some regimes value sacrifice more than others, or are less sensitive to mass death. Perhaps they are thus tempted to drag the world down with them: "you can never sleep completely peacefully when a nuclear power claims to be engaged in a holy war".

All in all, we can agree with the author's generally positive assessment of deterrence. Nevertheless, in the long term, peace between the great powers cannot be based solely on the threat of the worst devastation. The book concludes with a quote from Michael O'Hanlon, a specialist in US national security policy: "Deterrence may have been a minor factor in preserving peace in the past; that's debatable. But decision-makers need to be cautious and measured about how they conduct the experiment of testing this proposition".