In the Renaissance, Nicolas Machiavelli 14 extends the Aristotelian approach with his principle of Fortuna and Virtù, positing that nature is marked only by contingency (Fortuna). Thus, according to him, it is mainly character, determination, subjectivity and intuition (Virtù) that would enable the decision-maker to make timely and contingent choices to solve a problem. On the contrary, Descartes15 considers that it is only reason that makes us man (ego sum, ego existo 16). Only intelligence and pure reason would allow us to carry out action successfully. He proposes in his Discourse a method composed of four rules to avoid error. He develops a philosophy of doubt, aimed at reconstructing knowledge on certain foundations, referring to the certainty provided by mathematics.

During the Enlightenment, although dominated by the cult of science, Kant 17 takes the counterpoint of pure Cartesianism and questions the uncertainty and weakness of metaphysical argumentation having for object the knowledge of being (spirit, nature, God, matter, etc.), of the causes of the universe and of the first principles of knowledge. This approach leads him, in order to reinforce the metaphysical approach which he considers indispensable, to establish a critical examination of the possibilities of reason. Subsequently, seeking to move away from purely philosophical abstractions, Nicolas de Condorcet, a scientist and politician of the Enlightenment, proposes an original method of voting that allows one to choose rationally between several candidates. He thus formalized a decision-making process that he divided into three phases. The first concerns the principles that can constitute the general framework for decision-making and seeks to determine the different aspects of a problem, their implications and the options to be considered for decision-making. The second clarifies the issue and takes into consideration the opinions of the actors involved in the problem, compares and contrasts them, in order to retain only a limited number of them. The last phase consists in choosing an option on the basis of precise criteria chosen by the voters.

One of the earliest methods of tactical reasoning can be attributed to Sieur du Praissac in the early 17th century.

"Any military issue can be solved by, if, with whom, where, when, how, & how much..." 18. This excerpt reflects the need for every military leader of the day to take a rational approach to battle. Guibert 19Bourcet 20 and Joly de Mazeroy 21In the spirit of Enlightenment philosophy, they subsequently declined their own methods, seeking to determine the best way to frame decision-making in war.

One of the avatars of the Enlightenment was finally the positivist movement. Auguste Comte, both heir and critic of the Enlightenment, initiated this movement at the end of the 19th century. Positivism is characterized by the rejection of all metaphysical speculation and the idea that only the facts of experience and their relations can be objects of certain knowledge. This current had a very strong influence on a number of French officers after the defeat of 1870. Thus, General Jules Lewal, commander of the École supérieure de guerre from 1877 to 1880, conducted research and experiments for some twenty years that contributed to the re-founding of French military thought.

In 1892, he published an Introduction to the Positive Side of Strategy22. He also developed a method of tactical reasoning, the Lewal method, which prefigured what is deThe Lewal method prefigured the method for developing a tactical operational decision (MEDOT), which is now used by land forces23.

23 The intellectual filiation between Zénon d'Élée and MEDOT may seem bold because of the brevity of the above statement. Nevertheless, it is supported by texts, the oldest of which date back almost 25 centuries. This approach is intended to underline the intellectual roots of the Western, and more particularly French, decision-making culture. Since antiquity, a constant distinction has been made between a purely rationalist mode of decision-making and a purely empirical way of thinking. In the wake of Cartesianism, various theories have been put forward in an attempt to explain the phenomenon of decision-making and to describe a model that could make it more rational. Thus, throughout the history of thought in the West, scientific progress has always led to the temptation to adopt a purely scientific or procedural approach to access knowledge or solve a problem.

This distinction reveals in many thinkers a permanent search for a compromise between rationality and subjectivity in order to enable decision-making. It is Henri Bergson24who , at the beginning of the 20th century, finally best highlights this indispensable compromise to guide action. According to him, if intuition is different from intelligence, it is not opposed to it. Intuition is only possible at the end of a long intellectual effort, like a synthetic re-entry of the data analysed by intelligence. In addition, intuition can only be communicated with the help of intelligence. The determination of this compromise thus rests on Machiavelli's famous Virtù, on those intellectual and moral aptitudes proper to an individual, which make it possible, when confronted with a problem, to determine the best way to solve it.The determination of this compromise is thus based on Machiavelli's famous Virtù, on these intellectual and moral aptitudes of an individual, which make it possible, when faced with a problem, to set goals, acquire the appropriate knowledge and make choices in spite of the uncertainty, the hazards and the more or less important complexity of an environment. With the philosophers' conceptual framework in mind, let us study how these ideas have found an echo in the reflections of authors who have taken an interest in the phenomenon of war.

Strategists and the limited rationality of the leader in war.

Let us look at the way in which Western military thinkers and strategists, from the beginning of the eighteenth century, focused their reflections on the principles of decision and action in armed conflicts. These praxeological approaches made it possible to theorize in various ways the processes of acquisition of the knowledge necessary for the conduct of combat, but also to gradually establish a true Western philosophy from decision to war. In this section, we will not attempt to be exhaustive either, but will focus on authors who can usefully and simply characterize these different theories.

The reflections of most strategists have repeatedly shown that, up to the present day, several factors obviate or multiply theThe reflections of most strategists reveal, in a recurrent way and until today, several factors that hinder or multiply the ability to develop knowledge, i.e. to understand a situation, as well as to make decisions in combat. These factors relate mainly to uncertainty, largely linked to human nature, including that of the adversary, and to the indispensable intuitiveness of the leader in war to think and lead action.

From this observation, these thinkers deduce that it is mainly his subjective analytical capacities, the "eye", that condition a warlord's decision-making ability. Hervé Coutau-Bégarie summed up this assertion with simplicity: "the great leader is the one who understands and acts accordingly. This is very rare25. »

It is first of all interesting to note that among classical and neo-classical thinkers26 , French and Prussian authors27 have mainly nourished reflectionson war for almost three centuries. The Swiss Jomini is excepted, notwithstanding the fact that he began his military career as a volunteer in the army.e and that it was Marshal Ney, with whom he served, who helped him publish his Traité de grande tactique. Subsequently, the contributions of British thinkers such as Fuller and Liddel-Hart, while still of value, were more limited in scope and in some respects more partial and questionable. On the other hand, the mutual influences between French and Prussian military currents of thought were considerable and reached their peak with the works of Clausewitz and then Foch, fundamental in the construction of modern French military thought. With forerunners such as Frederick II,28 Maurice de Saxe,29 Guibert,30 andthen Bülow,31 to name but a few, the classical theorists, marked by thethe spirit of the Enlightenment in the eighteenth century, then by positivism in the nineteenth century, have sought to identify regularities in warfare. The determination of these regularities aims at establishing laws, universal principles whose knowledge would explain the victories of the past and would make it possible to win the battles or wars to come. The famous principles enacted by Foch, adapted and then adopted by the French army are the most relevant illustration of this. Also, these principles, which permeate military thought and doctrines of use of forces, are still today essential notions to guide the thinking of operational decision-makers and their staffs32. They are part of a culture and even a military identity in every country that has developed one. However, critics of such invariants to war argue that all these principles are likely to be invalidated by numerous exceptions drawn from military history. The universality and timelessness of such principles, erected as dogmas, are indeed questionable. Thus, Clausewitz established that "war is a chameleon that changes its nature with each engagement. "33 Foch thus insisted on the need to develop and know "fixed principles, to be applied in a variable way, according to the circumstances to each case, which is always particular and needs to be considered in itself. "34 As a result, the obedience of these principles does not seem to be as easy as it might seem, due to the uncertainty and complexity characterising any operational commitment. Clausewitz sums up the problem of wartime decision-making and the skills it requires in this way:

"War is the realm of uncertainty; three-quarters of the elements on which action is based remain in the mists of greater or lesser uncertainty. More than in any other field, it requires a subtle and penetrating intelligence that can discern and instinctively appreciate the truth. 35 "Clausewitz conceptualizes uncertainty around two essential notions: the fog of war and friction, to which are added the phenomena of chance and disorder. Subsequently, since "the unknown is the factor that governs war," in Foch's words, the decision-maker must conceive of action by integrating this fact, not by denying it. To do this, he develops a "limited rationality", in reference to the terms of the American economist and sociologist, Herbert Simon, taken up by General Vincent Desportes in his book Décider dans l'incertitude. Faced with an operational problem, it is therefore a question of adopting a mode of reasoning that is not inhibited by the inescapable constraints of war, namely the "war on terror".imperfect information, the impossibility of envisaging all the solutions and the inability to analyse them to the end of their consequences.

36 The theories of most strategists and their principles of warfare, however, do not adequately reflect the reality of warfare, the main essence of which remains man. Man, with his culture, his ideology, his intellectual, emotional and physical strengths and limitations, is at the heart of the problem of decision-making, especially in war. Ardant du Picq, taking the counterpoint of the positivist current and the sometimes purely scientific character taken by the studies on war in France, knew how to pertinently place this dimension in the debates of the beginning of the 20th century. "Fighting is the final goal of armies and man is the primary instrument of combat; there can be nothing wisely ordered in an army....e - constitution, organization, discipline, tactics, all things that stand like the fingers of a hand - without exact knowledge of the primary instrument, of man, and of his moral state at this definitive moment of combat37. "In times of war where the stakes are high and his very survival is sometimes at stake, the decision-maker may be subject to "a strong inhibition that limits his capacity for reflection and an intense need to act38. 38 "The psychological and emotional tension in combat affects, more than in any other field, the decision-making abilities of individuals, sometimes to the point of astonishment. The work of the American neuroscientist Antonio Damasio has since confirmed that decision-making is in fact largely influenced by emotions. 39 Emotions are said to play a key role in what is referred to as "intuitive decision-making". Similarly, social intelligence, or interpersonal intelligence, which enables us to understand others (our thoughts and feelings) and to interact effectively in situations of collaboration, negotiation or confrontation, is an essential aspect of the ability to obtain an appropriate understanding of an environment and an adversary.

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14 Machiavelli, Nicolas (1469 - 1527), L'art de la guerre, Tempus, 2011 and Le Prince, Folio classiques, 2007.

15 Descartes, René, Discours de la méthode. Pour bien conduire sa raison et chercher la vérité dans les sciences, 1637, Flamarion, reprinted 2005.

16 Descartes, René, Méditations métaphysiques, 1641, Flamarion, reprinted 2005.

17 Kant, Emmanuel, Critique of Pure Reason, 1781, Folio, reprinted 2015.

18 du Praissac, Briefve méthode pour résoudre facilement toute question militaire proposée, Paris, 1614, (https://books.google.fr/books?id=nYT83D83LuEC&printsec=frontcover hl=fr#v=onepage&q&f=false).

19 de Guibert, Jacques-Antoine-Hippolyte, Essai général de tactique, précédé d'un discours sur l'état actuel de la politique et de la science militaire en Europe, associated booksellers, 1772, http://gallica.bnf.fr/ark:/12148/bpt6k5408326q/f1.vertical , reprinted. Economica, 2004.

20 de Bourcet, Pierre-Joseph, Principes de la guerre en montagne, 1775,(https://gallica. bnf.fr/ark:/12148/bpt6k86486q), reprinted. Hachette, 2016.

21 Joly de Maizeroi, Paul-Gédéon, La tactique discutée et réduite à ses véritables principes, Paris, 1773.

22 Lewal, Jules, Introduction to the Positive Part of Strategy, L. Baudoin, 1892.

23 Interested readers may usefully refer to the thesis for the doctorate in history of General Michel Delion at the Ecole Pratique des Hautes Etudes, Histoire de la méthode de raisonnement militaire, 2014 (http://www.theses.fr/2014EPHE4037).

24 Bergson, Henri, La pensée et le mouvant, 1934, Alcan, Flammarion, 2014.

25 Quoted in Lecomte, Pauline, L'historien de la stratégie, Hervé Coutau-Bégarie, La Nouvelle revue d'Histoire, nº 33, 2007.

26 Interested readers will usefully refer to the work of Hervé Coutau-Bégarie, who distinguishes the classical strategists (from the origins to the end of the 18th century) from those of the "classical" strategists.cle), neo-classical (19th and early 20th century) and modern (from 1945 onwards) in Coutau-Bégarie, Hervé, Traité de stratégie, Economica, 1999, reprinted in Coutau-Bégarie, Hervé, Traité de stratégie, Economica, 1999, reprinted. 2011.

27 Langendorf, Jean-Jacques, La pensée militaire prussienne. Studies of Frederick the Great in Schlieffen, Economica, 2012.

28 Frederick II, Discourse on War (1750) and Military Instruction of the King of Prussia for his Generals (1755). http://friedrich. uni-trier.de/fr/

29 de Saxe, Maurice, Mes rêveries, Durand, 1757, http://gallica.bnf.fr/ark:/12148/bpt6k865593/f1.vertical,reprinted. Economica, 2015.

30 de Guibert, op. cit.

31 von Bülow, Dietrich, Esprit du système de guerre moderne, destiné aux jeunes militaires, 1799,(http://gallica.bnf.fr/ark:/12148/bpt6k86490z) quoted in Coutau-Bégarie , Hervé, Traité de stratégie, Economica, 1999, reprinted 2011.

32 Clée, Fabrice, Les principes de la guerre : clarification sémantique, point de situation et cadre de départ pour de nouvelles réflexions doctrinales. Lettre de la doctrine n°9, CDEC, 2018.https://www.penseemiliterre.fr/ressources/30084/43/lettre-09.pdf.

33 von Clausewitz, Carl, De la guerre, 1832, reprinted. Tempus, 2014.

34 Foch, Ferdinand, On the Principles of War. Lectures given at the École supérieure de guerre, Berger-Levrault, 1903, http://gallica.bnf.fr/ark:/12148/bpt6k86515g/ f6.vertical, reprinted. Economica, 2007.

35 von Clausewitz, Carl, op. cit.

36 Desportes, Vincent, Deciding in Uncertainty. Economica, 2004.

37 Ardant du Picq, Charles, Etudes sur le combat : combat antique et combat moderne, R. Chapelot, 1903, reprinted.Economica 2005. http://gallica.bnf.fr/ark:/12148/ bpt6k750536?rk=42918;4

38 Goya, Michel, Sous le feu : la mort comme hypothèse de travail, Tallandier, 2014.