Dense and clear, "Why Deterrence" openswith two contemporary crises, emblematic of the international use of deterrence: the Syrian chemical crisis and the Ukrainian crisis. The approach consists in questioning the conditions for the use of force and the protection of the collective interests of the planetary community (in other words, peace) in the face of "non-cooperative actors" who see in any negotiation a sign of weakness.

The exercise is complex, subtle and often discouraging, as the slightest incident in the field can rekindle the fire. The Syrian lies, the lack of credibility of North American tactics, the forced adaptation of deception strategies and the lack of a clear understanding of the Syrian strategy are all factors that have contributed to the complexity of the exercise.The story of Syrian lies, the lack of credibility of North American tactics, the forced adaptation of defence strategies, and the nuclear dimension of the Ukrainian imbroglio are examined at length, leading to the extension in time and space of irremediable quarrels. Deterrence," explains Nicolas Roche, "is a grammar, a language of power that aims to control the escalation of a conflict," if not prevent it. This requires military capabilities, appropriate diplomatic language and adequate acts of intimidation, giving concrete expression to political discourse.

In the first part, the author traces the example of France in an approach that is both historical and technical. Then, the description of the nuclear aspect of deterrence is discussed at length, because "everything is there": how to destroy the violence of the other without destroying oneself...The main concepts of deterrence, from a graduated response to massive retaliation, are set out with great clarity, from which emerges the need to have credible, lasting and constant interlocutors in their objectives. This is not always obvious.

The danger is great, almost constant. The more interlocutors who possess nuclear weapons, the more serious and difficult it will be to control the risk. "Drowning the fish" is a stubborn and physically dangerous brain sport. How far should we go, how, where and why should we stop measured violence and offensive dialogue? The dosage must be reviewed and corrected as incidents occur. Our now almost instantaneous information system does not help.

The final sections of the book describe in great detail the possibilities of cyber defence and, above all, give an international picture of deterrence strategies in the face of constant turbulence: in the final analysis, the scourge of "globalisation" is the interdependence of all, everyone and all disagreements. Blessed are those who learned of the Lisbon earthquake a year late!!!!

Basically, there would be the "old wise men" of nuclear power, those who since 1946 have known that it should not be used, in other words the five members of the Security Council, and then the others....the little troublemakers of modernity: the ambiguity of Israel, the silent and sophisticated magma of Iran, the immediate dangerousness of North Korea.

The author returns at length to these various aspects - fascinating pages 263 to 357 - the possible anti-missile strategies, the entry of exo-atmospheric space control into the arsenal of consultation and dissuasion; he highlights, in passing, the wanderings, blunders and contradictions of North American policy.

The conclusion, a kind of "no conclusion", brings back to the fore the two foundations of our international law: morality and the principle of the commonly accepted rule. The disastrous consequences of the indiscriminate use of nuclear weapons, the illegality of this use, the principle of proportionality of responses to the threat of nuclear weapons, the principle of the rule of law and the principle of the rule of law as a whole. The disastrous consequences of the indiscriminate use of nuclear weapons, the illegality of such use and the principle of proportionality of responses to aggression are all barriers that are painstakingly erected in the course of conflicts, but which prove to be very weak in the face of definitive ill will. Can religion - of any kind - be an asset or an accelerator of disaster?

Nuclear deterrence, in any case, remains the key and foundation of global management strategies.

A fine work, certainly more philosophical than it sounds.

Nicolas Roche is the head of the Interdisciplinary Centre for Studies on Nuclear Energy and Strategy at the École Normale Supérieure (Ulm). A graduate of ENA, he has held various positions at the Ministry of Foreign Affairs, the Ministry of Defence and the CEA. His authority is internationally recognized. The book is also the literary and technical development of his various teachings.