1War has not become a thing of the past. It is true that since 1945 the international system has experienced a “long peace”,  characterized by the lack of a “major war”,  and, today, even by the lack of the “risk of major war”  between the great powers. Similarly, the number of armed conflicts, between or within states, is decreasing.  The increasing scarcity of war, however, does not mean it has disappeared altogether. Reminders of this have been the recent French military interventions in Afghanistan, Libya, Mali, Iraq, and Syria, and more to the point, the series of terrorist attacks on French territory since 2015. Perhaps these events point to a possible renaissance of war—at any rate they point to a return of war  to our shores with the intermittent return of political violence to the day to day lives of the French. What is more, the attacks have brought about the re-emergence of the topic of war in political discourse and public debate.  The persistence of war and its topicality today have been accompanied in France by a desire to reassert the value of the academic study of war. In an opinion piece published in Le Monde following the attacks on 13 November 2015, a group of researchers, mainly political scientists, criticized the lack of “institutional and scientific recognition of the academic study of war” and advocated the need to “think about war”.  This initiative coincided with the launch of a new association, the Association for the Study of War and Strategy (AEGES), which encourages dialogue amongst researchers and seeks to lend fresh impetus and legitimacy to war research.
2The aim of this article is to contribute to the renewal of war studies in France by analyzing the nature of war itself. Our objective is to demonstrate that there is a persistent ambiguity in the ontology of war and that in the literature there are three differing conceptions of war. In order to highlight these rival conceptions, we will carry out a detailed analysis of one of the most famous definitions, that of Carl von Clausewitz, which Raymond Aron nicknamed “the Formula”: 
War is merely the continuation of [politik] by other means. 
4Clausewitz is the author of a major work on war  which is now considered both a classic of military literature and a great work of political philosophy and theory.  This work has given rise to numerous analyses of war within the social sciences in France. There is a lengthy tradition of engaging with Clausewitz’s writing, which has been mapped by Benoît Durieux in his thesis on the reception of Clausewitz.  The principal authors to have dealt with Clausewitz’s thought include Raymond Aron,  whose interpretation of On War is one of the most accomplished, even if his optimism has been criticized,  and Éric Weil,  whose 1955 article in the Revue française de science politique is one of the first to take an interest in the political dimension of Clausewitz’s work. Further analysts include André Glucksmann, Julien Freund, Emmanuel Terray, and more recently, René Girard.  Michel Dobry, who wrote a thesis on Clausewitz, even proposes a “Clausewitzian perspective” in his Sociologie des crises politiques. 
5The importance and durability of Clausewitz’s contribution to the analysis of war—witnessed by the dynamic nature of Clausewitzian studies  in recent years—is a result of the two-fold ambition of the theorist. Firstly, his intention was to show the causal factors of violent confrontation between armies, but not to give them practical lessons on how to achieve successful outcomes. He believed that “theory should be study, not doctrine”  whose purpose was to set out the “major characteristics of military activity”.  In particular, Clausewitz’s desire was to carry out an “analytical investigation leading to a close acquaintance with the subject”.  In other words, he aimed to discover the set of factors that, varying according to the epoch, might influence the conduct of military operations and armed combat itself. Thus his goal was to develop as comprehensive a theory as possible that would be capable of “transcending the particularities of time and place”.  Secondly, in the last years of his life, from 1827 to 1831, Clausewitz sought to give an account of the uniqueness and the diversity of war. He believed that despite their multiple forms, all wars had something in common, which made it possible for them to be grouped under the name of war. He thus introduced a distinction between the nature of war, which was immutable, and the individual characteristics of each war, which were variable, and for which he coined a metaphor, asserting that war in fact was a “true chameleon”.  Thus, his analysis was structured around a two-fold objective: on the one hand, to think about the concept of war, “to grasp the nature of war”,  and on the other hand, to bring to light the factors determining the individual characteristics of each war.
6The Formula is certainly one of Clausewitz’s most debated contributions. During the Cold War, it was notably at the heart of a series of works that advocated the need to prioritize political considerations over military ones as the only way to limit violence and avoid nuclear apocalypse.  Likewise, it has also been frequently inverted  and condemned.  Since the end of the Cold War, it would seem that Clausewitzian studies have shifted their focus to other aspects of Clausewitz’s work, notably the “paradoxical trinity”,  which he sets out at the end of Chapter One of Book One of On War. 
7While the Formula has long been debated in the literature, it seems to us that one essential element has been generally ignored: the Formula contains three possible definitions of war, which, while different, exist side by side in Clausewitz’s work, particularly in Chapter One of Book One, generally considered to be “his masterpiece”.  Paradoxically, this key chapter seems to contain passages that are amongst the most contradictory and ambiguous in the work. The Formula contains two successive ideas: the assertion that war is the continuation of “politik”, and then the introduction of the question of “other means”. These two ideas, however, are highly ambiguous. Firstly, the notion of “politik”, of which war is supposed to be the continuation, is not defined clearly by Clausewitz. As Christopher Bassford explains, saying “that war is an expression of X, without defining X, gets [us] nowhere”.  This lack of definition is all the more problematic as the term “politik” is particularly vague. There are two words in English to render the German word “Politik”—policy and politics—and translators and commentators, incapable of choosing, alternate between them, at the risk of perpetuating the confusion over the real meaning of the Formula.  We will demonstrate that the traditional interpretation of the Formula conceives of war as a political instrument, that is to say, as a means of action that organized groups can resort to in order to achieve a given objective. Yet, this conception of war as an instrument—which Clausewitz himself promotes on a number of occasions—is at odds with the parallel assertion that war is interactional: war cannot be both a tool available to organized groups and the interaction of two organized groups.
8Secondly, the second half of the Formula referring to “other means” is also ambiguous. In fact, Clausewitz does not specify in Chapter One of Book One if war encompasses the use of these “other means” exclusively or if it encompasses the use of all means at the disposal of social groups (in times of war and of peace), which of necessity include these “other means”. In other words, is violence the only means of war or simply one of several? The difference is significant. If the first, war could be summed up as being only the violent confrontation of rival groups. It would be the geographically constrained confrontation between two rival armies. If the second, it could be seen as one of the various relationships between organized groups. In the same way as peace, it would be one of the alternative phases of interaction between social groups.
9The dual ambiguity of the Formula leads to three different definitions of war: It can be thought of as a political instrument, as the name given to the violent confrontation between armies, or as the name given to one of the forms of bilateral interactions between organized groups. These three conceptions exist side by side in Clausewitz’s major work. There is, therefore, at the heart of one of the most famous works on war, a contradiction over the nature of war itself. The three distinct conceptions contained in the Formula do not, as far as can be seen, make war a concept that is essentially contested, in the sense proposed by Walter Bryce Gallie.  Indeed, the fact that the different conceptions co-exist in the work of Clausewitz and those who interpret him, and more generally, in that of writers who are interested in war, demonstrates a certain lack of rigor in the use of the concept and points more to confusion than to contestation, to pick up a distinction established by David Collier, Fernando Daniel Hidalgo, and Andra Olivia Maciuceanu.  This causes one to reflect on the fact that certain ambiguities and incoherence in both the everyday and academic use of the term of war may have been overlooked. Thus, there is a need to clarify the concepts that we intend to tackle.  In particular, we propose to link the three definitions that emerge from the Clausewitzian formula to three distinct concepts: armed violence (which is a political instrument), the violent confrontation of armies (the name given to the clash of the armed forces of the warring parties), and war (conceived as one of the alternative phases in relations between social groups).
10This article is divided into two parts. Firstly, we look at the first half of Clausewitz’s Formula and show that the traditional interpretation—which conceives of war as a simple political instrument, as a means of action that organized groups can resort to in order to achieve their objectives—is at odds with Clausewitz’s repeated idea of the interactional nature of war. Secondly, we look at the “other means” in the Formula and reflect upon whether war encompasses only the use of violence or if it involves the use of all the means at the disposal of organized groups alongside the use of violence.
The First Half of the Formula: War as the Continuation of Politik
The Ambiguity of Clausewitz
11Clausewitz places the notion of politik at the heart of the first part of his definition of war. However, the clear link—war being the continuation of politik—is obscured by the ambiguity with which the idea of politik is treated in the Prussian theorist’s work. In fact, Clausewitz never defines clearly what he understands politik to be. Moreover, he tends to use two different conceptions. His two uses of the concept of politik result in two competing conceptions of war in his work.
12Let us look first at the definition of politik that seems at first sight to be the most fully developed, the one he sets out formally on two separate occasions. The first time, in Chapter One of Book One, Clausewitz describes politik as “the product of [the state’s] brain”, that is, “if the state is thought of as a person”.  The second time, at the end of the work in Chapter Six of Book Eight, he says that we can only “treat [politik] as representative of all interests of the community”.  Raymond Aron’s reading of these two quotations prompts him to assert that Clausewitz was using the term politik as “the equivalent of what writers of today call the ‘national interest’”.  War is then at the service of the national interest, an instrument of the “community” to promote its interests; war is a means to an end: war is a political instrument. Clausewitz himself wrote:
We see, therefore, that war is not merely an act of [politik], but a true political instrument. 
14This conception leads one logically to believe that the recourse to war is undertaken unilaterally: a social group sets itself an objective and attempts to reach it by resorting to a particular means—here, war. The instrument of war can be used simultaneously and reciprocally by two actors—that is to say, it can be employed within the context of a relationship—but this is a rather specific use, which is not connected to the essence of war. The first conception of politik presented by Clausewitz thus results in a definition of war as an option at the disposal of social groups—a means of action whose employment must of necessity be unilateral given the individual intentions of each group. However, Clausewitz does not solely use this first conception of politik and tends, in a way that is never clear and explicit, to promote a second. These two conceptions of politik rub shoulders in his text in a somewhat confusing manner. Thus the quotation above is continued in the following way:
We see, therefore, that war is not merely an act of [politik], but a true political instrument, a continuation of political intercourse, carried on with other means. 
16By substituting the term politik with political intercourse, Clausewitz invites us to think of politik as a relational phenomenon, or as an interaction. The use of politik and political intercourse as synonyms is confirmed in a symbolic manner in Chapter Six of Book Eight, when Clausewitz proposes a new version of the Formula that is slightly different from the one in Chapter One of Book One:
War is simply a continuation of political intercourse, with the addition of other means. 
18These two different definitions of politik are clearly contradictory: war cannot be at the same time a political instrument (which involves unilateral implementation) and political interactions (which involve the existence of two interacting actors).
The Traditional Interpretation of the Formula: War Conceived as a Political Instrument
19Faced with the two contradictory definitions of war provided by Clausewitz, most writers have decided in favor of the first one. The traditionally predominant interpretation of the Formula makes war a simple instrument in the service of a political end. As Thomas Waldman points out, “the name of Clausewitz is almost synonymous with the idea of war as an instrument of policy”.  According to this interpretation of the Formula, war must be considered a means of action for political groups on the international scene. For Herbert Rosinski, “war is one of the means with which politics seeks to achieve its objectives”.  In this sense, war becomes the partner of diplomacy, and is only different in that it is violent. Consequently, social groups have two tools—war and diplomacy—which they may use freely in their relationships with other groups. Depending on the circumstances, they can choose the tool that seems the best adapted to promote their interests and meet their objectives. For Dario Battistella, a “‘serious means to a serious end’, war is, in Clausewitz’s view, ‘merely the continuation of policy by other means’, in other words, the tools that a state resorts to when diplomacy is perceived, rightly or wrongly, as being unable to obtain satisfaction in the course of a contentious interaction with another state”. 
20War is thus a means of action, one that is implemented in the pursuit of a political end—and this political end is its raison d’être. For Raymond Aron, “the instrument, by definition, or the tool, is made to be used; it is used in order to do something. Thus war is undertaken to pursue the end which is dictated by politics”.  For General Desportes, “the clarity of Clausewitzian thought results from the clear distinction it makes between ends on the one hand and means on the other; this differentiation is the basis of the argument. For Clausewitz, war belongs to the second element; far from being an end in itself it exists by merit of the objective that gives it is meaning. [...] It is decided on and carried out in order to achieve an end that transcends it: political intention”.  The general’s analysis is firmly rooted in one of Clausewitz’s most famous phrases:
The political object is the goal, war is the means of reaching it, and means can never be considered in isolation from their purpose. 
22The resort to war in order to achieve a political aim is thus provided with a rational basis. This signifies that the theory implies a process in which all the options available to the head of state are evaluated before a decision is reached on which means will be employed. Consequently, social groups choose consciously to resort to war when they consider it to be the best adapted instrument to achieve a given aim.  Specifically, war will only be undertaken “when its utility is greater than the utility of not resorting to armed force”.  All in all, the traditional interpretation of the Formula leads to a conception of war as a legitimate and rational instrument available to organized groups to assist them in achieving their political objectives. This conception leads logically to the consideration of Clausewitz as one of the precursors of the realist school of international relations. 
War as a Relational Phenomenon
23Thus we have seen that the traditional interpretation of the Formula leads to the definition of war as a political instrument, that is to say, as a means of action employed by organized groups in order to achieve a given objective. This first definition, and the unilateralism it implies, is clearly at odds with Clausewitz’s assertion that war is interactional.
24Throughout his work, Clausewitz reiterates the relational characteristic of war. Moreover, he introduces the idea on the very first page, a sign of the importance he accords it:
I shall not begin by expounding a pedantic, literary definition of war, but go straight to the heart of the matter, to the duel. War is nothing but a duel on a larger scale. 
26The etymological proximity of war and duel in Latin is undeniable. The word “duel” comes from duellum, which is itself an archaic form of bellum. The word bellum  means war or combat, and has given rise to many words in English, such as belligerent. In its modern use, a duel is a particular kind of combat involving two combatants. By comparing war to a duel, Clausewitz’s intention is to present war as a clash between two adversaries. The fact that the duel takes place “on a larger scale” simply indicates that war doesn’t involve two individuals but two groups. Clausewitz implies that the groups must be organized: both groups must be cohesive and coordinated in order to be considered united, that is to say, metaphorically, as duelists. This brings us to the collective nature of war. War is the interaction of organized groups. According to Raymond Aron, “war is the conflict of one form of organized behavior with another, the trial by force between ‘groups’, each of which strives to gain victory over the other by multiplying the vigor of each combatant by discipline. In this precise sense, war cannot be anterior to the formation of groups. A social phenomenon, it implies society by definition”.  The parallelism between war and duels that Clausewitz describes has two consequences. Firstly, it makes reciprocity between the two adversaries an essential condition for war. Secondly, it makes defense, and not attack, the factor that leads to a state of war.
27Firstly, war causes conflict between two adversaries who both use violence against each other. This presupposes, as Gaston Bouthoul has noted, “an active enemy fully aware of pursuing a destructive goal. This involves conscious, reciprocated action”.  The adversary cannot be a passive and willing victim, who endures repeated attacks. On the contrary, the adversary seeks to anticipate the enemy’s movements, to dodge their blows, to counter-attack, and so on; it plans offensives and adapts to the circumstances, thus setting its intelligence against the intelligence of the other. War requires confrontation; it involves mutual violence. In this sense, war presents a permanent danger for both warring parties. Clausewitz wrote:
War, however, is not the action of a living force upon a lifeless mass (total nonresistance would be no war at all) but always the collision of two living forces. The ultimate aim of waging war, as formulated here, must be taken as applying to both sides. Once again, there is interaction. So long as I have not overthrown my opponent I am bound to fear he may overthrow me. 
29The Prussian theorist makes it clear that war involves reciprocal action and violent intent and is thus a phenomenon involving a relationship.
[war does not belong to] the realm of arts and sciences; rather it is part of man’s social existence. [...] The essential difference is that war is not an exercise of the will directed at inanimate matter, as is the case with the mechanical arts, or at matter which is animate but passive and yielding, as is the case with the human mind and emotions in the fine arts. In war, the will is directed at an animate object that reacts. 
31And Clausewitz concludes:
War is an act of human intercourse. 
33If war implies reciprocity in intended action, the logical conclusion is that the absence of reciprocity in the use of violence means the absence of war, in other words, peace.  Peace is therefore defined by involving non-reciprocity in the use of violence. This encompasses both the complete absence of violence, but also the unilateral use of violence.  When only one of the two actors involved in the conflict has chosen to take up arms, this is not war, but peace. In order for war to exist, it is necessary for both adversaries to decide to employ violence against each other. Thus, an organized group may resort to armed force in order to pursue a political aim without this in itself being war. The invasion of Austria by Nazi Germany in March 1938 in order to carry out the Anschluss therefore cannot be considered to be a war, since, though the Wehrmacht used force, there was no resistance from the Austrian side. In the same way, the German operation in Denmark in April 1940 cannot be considered to be war as the Danish government refused to fight against the invader. Conversely, when the Hitler regime wished to conquer Poland in 1939 and was confronted by an admittedly relatively weak adversary, but one that was determined to resist with force, this can rightly be called war.
34Secondly, it seems that if war requires at least two participants, it is not those who attack who are responsible for initiating war but rather those who defend. For Clausewitz, a state of war does not exist until invasion has provoked defense.  In fact, until the attacker is met by the resistance of the defender, he is the only one to have chosen to resort to arms: there is no reciprocal action and therefore there is no war. For Dario Battistella, “as a result of an interaction between two or more states, or, more generally, between two or more combatant political units, war [...] only starts at the point when there is armed defense by a unit, or at the least the will to engage in armed defense, in the face of an armed attack by the other political unit”.  The need for the victim to respond to the aggression of his rival implies that, in order for war to exist, the defender must choose war, in other words, the defender must decide to respond with violence. The victim of an attack may well be in a precarious position and must respond to what is a reality. However, there is room for maneuver in the response and a choice must be made between different alternatives, notably with regard to which instruments are employed. The defender is in no way obliged to use violence, but free to use it or not to use it. In fact, the outbreak of war clearly depends on the decision of the victim. As Bernard Brodie puts it, “one must [...] observe that war is an act of choice. A small state may have no influence over the events that lead to its being invaded, but it does choose whether or not to resist”.  War must therefore be seen as a voluntary phenomenon: it only results from the joint decision of both camps to resort to armed violence. This being so, one must give up the idea that wars can be accidents. As Thomas Schelling comments, “it is not accidents themselves—mechanical, electronic, or human—that could cause a war, but their effect on decisions. Accidents can trigger decisions, and this may be all that anybody has ever meant; but the distinction needs to be made”. 
The Distinction between War and Armed Violence
35Clausewitz’s assertion that war’s nature is interactional challenges the traditional interpretation of the Formula. War cannot be both a means at the disposal of social groups—which they can use to achieve a given objective—and the interaction of two organized groups who use violence against each other. The instrumental view of war and the unilateralism that it implies can clearly not be reconciled with the dyadic view of war that is defined by the presence of reciprocity in the use of violence. While Clausewitz does indeed advocate these two conflicting conceptions in his work, there are two reasons for believing that the latter is the most faithful to his thinking. Firstly, the interactional nature of war is without doubt one of the central premises of his theory and occupies a central position in his work.  Secondly, Clausewitz proposes, as we have pointed out, a modified version of the Formula in Chapter Six of Book Eight, which introduces the idea of war as “a continuation of political intercourse”. The addition of the term “intercourse” is certainly not insignificant: it both gives an indication as to the nature of war (as a relational phenomenon) and the meaning that Clausewitz attributed to the notion of politik. From this point of view, it would be right to conceive of politik as the relations that are maintained between warring parties, both in times of war and in times of peace. Some authors, notably Raymond Aron and Benoît Durieux, have already advanced this interpretation of the idea of politik in Clausewitz’s work. Aron defines the “[politik] that continues during the hostilities” as the “commerce in the sense of the seventeenth and eighteenth centuries, the communication between states”;  the “political element” that Clausewitz evokes should be “understood as the relationship between hostile states”.  In the same way, Benoît Durieux, opposing the traditional interpretation of the Formula, writes that “if war is the continuation of [politik] by other means, it is [...] rather in the pursuit of dialogue with the other by the arguments belonging to the armed force rather than by the simple employment of the military instrument. [...] The [politik] that is continued by the means of military action is less an objective than a process of relations”.  The relational conception of politik suggested by Raymond Aron and Benoît Durieux supports a reinterpretation of the Formula that is coherent with Clausewitz’s assertion of the interactional nature of war: Clausewitz’s Formula would mean that war is the simple continuation of relations between social groups, that is to say, “takes its place in a continuity of relations always controlled by the collectivities’ intentions toward each other”. 
36This reinterpretation of the Formula not only seems the most faithful to Clausewitzian thinking but also more convincing with regard to the resulting definition of war. In our opinion, the instrumental conception of war that is supported by the traditional interpretation of the Formula suffers from a weakness that is worth highlighting: it defines war in a sense that is generally attributed to the idea of violence, in other words, as a means of action that can be employed unilaterally in pursuit of a given end. This being so, we believe that the traditional interpretation of the Formula, by taking violence and war to be synonymous, blurs the boundaries between two quite distinct concepts. If one admits that war cannot be confused with violence, one should also reject the traditional interpretation of the Formula, and, de facto, think of war not as a political instrument but as the political interaction of two organized groups, both of which resort to violence.
The Second Half of the Formula: The Means of War
War Considered to Be a Violent Confrontation between Two Armies
37We have just defined war as the interaction of two organized groups who employ armed violence against each other. One should now consider the nature of this interaction. The second half of the Formula can help to do this. As was pointed out in the introduction, the wording of the Formula in Chapter One of Book One (“by other means”) is ambiguous. It can be interpreted in three different ways. Firstly, one can consider that the means peculiar to war substitute the means peculiar to peace (war thus being the continuation of political relations conducted in times of peace but using different means). Secondly, it is possible to believe that the employment of warlike means would not necessarily require the cessation of peaceful means, but that only these particular means would now belong to war, properly speaking. Finally, one can interpret the passage as signifying that the means employed in times of peace remain available in times of war, and that, moreover, their use is an integral part of war itself, in the same way as is the use of violence.
38The first of these three interpretations must be discarded at the outset. In fact, it is clear that the decision to resort to violence is not automatically accompanied by the renunciation of all non-violent tools available to organized groups. Violence does not systematically substitute social groups’ other instruments of external action, but can co-exist with them. Consequently, the question that one should respond to relates to whether non-violent means should be considered to belong to the domain of war. In other words, if one admits that organized groups can persist in the use of non-violent means alongside the application of armed force, is it also necessary to consider that the use of these means is an integral part of war? An affirmative answer to this question implies a definition of war as the interaction between two organized groups who resort to a range of different means, one of which is armed violence. Violence is indispensable to war—it is war’s sine qua non—but it does not in itself constitute the only means by which war is carried out. A negative reply, however, is tantamount to refusing to include the use of non-violent means in the domain of war. War is reduced to being the military dimension of the interactions between social groups and co-exists alongside their non-violent interactions.
39The everyday use of language would seem to support the second hypothesis. Popular expressions such as “setting off for war”, or “theater of war” locate war in a specific spatial framework: they confine war to the geographic location in which armies act and confront each other. In the same way, the ordinary use—or omission—of the expression “wage war” is revealing. One accepts that soldiers wage war; on the other hand, one would not say that diplomats wage war. Thus war would be a military affair, which diplomats do not engage in. All these expressions therefore associate war exclusively with the use of violence. Beyond everyday language, the same tendency to reduce war to the mere conduct of military operations is evident in the numerous works relating to strategic thinking. The tendency is noticeable when authors engage in a classic—if not indispensable—exercise of strategic thinking: the enunciation of principles of war. The aim of these principles is to explain how war should be undertaken. Yet, it seems that these lists relate  systematically to the conduct of an army in the theater of war, even—as Antulio J. Echevarria II points out—to the study of battle.  In this respect, the art of war has long been defined as the art of carrying out military operations. Thus, there is a long and rich tradition at the heart of strategic thinking that reduces war to the confrontation of armies and confines war to the military sphere. Clausewitz’s thought is broadly in line with this tradition. Indeed, his first works are consistent with traditional strategic thinking and in them he sets out to discover the secrets of the art of war, which he confuses with the military arts. For example, in a text dated 1804, Clausewitz demonstrates his preference for “the most decisive operations, even if they demand supreme effort! This principle is in the nature of the art of war”. 
40Several lines later he goes on to say:
The art of war prefers the most decisive operation to the most certain. 
42In the same way, in an 1812 text addressed to his former pupil, the crown prince of Prussia, Clausewitz attempts to highlight the “essential principles in the conduct of war”.  Advice on war planning—including a sketch of the principle of the concentration of forces—rubs shoulders with some more original ideas, which prefigure certain ideas found in his treaty, On War—notably the importance of moral forces.
The theory of war is concerned in the first instance with the manner of obtaining a decisive advantage in terms of armed forces and other physical advantages; but if this goal cannot be attained, theory teaches us to count on facts of a moral nature: probable faults of the enemy, the impression produced by an audacious venture, etc. and even our own despair. None of this is foreign to the domain of the military art and its theory, being nothing but a considered examination of all the situations where war might place us. 
44This quotation betrays the fact that Clausewitz identifies the military arts with the art of war. This propensity to reduce war to the military relations between social groups is not limited to the early work of the Prussian theorist: it is also found to a large extent in his mature major work, On War. Clausewitz dedicates five of the eight books in this work to explicitly military questions: strategy, engagement, military force, defense, and attack. In the three remaining books, dedicated to the nature of war, the theory of war, and planning for war, almost all his analysis is concerned, directly or indirectly, with questions related to the military arts and combat. When he reflects upon moral forces, the genius for war, the permanence of danger, and so on, he makes an essential contribution to our understanding of the violent dimension of war, but he tends to ignore war’s non-violent aspects. Clausewitz seems to consider that war only has one means at its disposal: armed violence. Thus he writes
The conduct of war, then, consists in the planning and conduct of fighting. 
46He expresses himself even more clearly in Chapter Two of Book One, which is dedicated to the purpose and the means of war:
Let us now turn to the means. There is only one: combat. However many forms combat takes, however far it may be removed from the brute discharge of hatred and enmity of a physical encounter, however many forces may intrude which themselves are not part of fighting, it is inherent in the very concept of war that everything that occurs must originally derive from combat. 
The Distinction between War and the Violent Confrontation of Armies
48Clausewitz tended to reduce war to the violent interaction of warring parties, in other words, to define it as exclusively the confrontation between rival armies. Yet, some passages of the treaty On War, and notably the modified version of the Formula in Chapter Six of Book Eight, reveal a different, broader conception of war:
War is simply a continuation of political intercourse, with the addition of other means. 
50He goes on:
We deliberately use the phrase “with the addition of other means“ because we also want to make it clear that war in itself does not suspend political intercourse or change it into something entirely different. In essentials that intercourse continues, irrespective of the means it employs. 
52These quotations contain two ideas that seem essential: firstly, the idea of the ongoing nature of political intercourse between organized groups, in times of peace as in times of war, and secondly, the idea that war is distinct from peace by the addition of reciprocal violence. This two-fold understanding was not fully exploited by Clausewitz, who either didn’t perceive it or didn’t spell out the logical implications. In fact, it is impossible to know if these passages indicate a possible evolution in the writer’s thinking, or if they reveal difficulties experienced by the theorist in clarifying his ideas.  The fact remains that they contain the seeds for an expansion of our understanding of war.
53The modified version of the Formula, by alluding to “the mixture” of mutual violence, implies that all non-violent means available to social groups can be employed as part of intercourse during times of peace and times of war. This means that resorting to non-violent means—alongside violence—is an integral part of war itself. As Aron has pointed out, “war, without losing its violent character, is found to be inserted in the course of relations between states, a course which does not interrupt the eruption of violence. Combat should thus [...] lose its character of being the exclusive means.”  He goes on to say that because relations between states are maintained during hostilities, the means of peace continue to be available in times of war, and that one goes into battle instead of just sending notes, but one carries on sending notes, or the equivalent of notes, whilst one is in battle.  Hence, war cannot be reduced simply to the reciprocal use of violence but also encompasses the non-violent means available to organized groups. This conception of war no longer recognizes the exclusive nature of mutual violence but does not negate its specificity. To say that war is not reduced simply to violence does not imply that violence is considered to be a means like any other. On the contrary, it is precisely because violence is seen to be an exceptional means of action that its use constitutes the criterion that differentiates war from the absence of war.
54This way of perceiving war has gradually become more common during the twentieth century, particularly with the emergence of the idea of “total war”, which was posited by Erich Ludendorff following the First World War.  War here is described as total because it implies the unprecedented mobilization of the population as well as the participation of all sectors of society in the war effort; it also accepts that the confrontation legitimizes all means of action and cannot be limited only to armed violence. General André Beaufre thus wrote that “everyone knows that war today is total [...]; in other words it will be carried on in all fields, political, economic, diplomatic and military”.  This recognition of the non-military dimensions of war has led to an expansion of another concept closely linked to the conduct of war, the concept of strategy. Initially defined as the “the art of distributing and applying military means to fulfil the ends of policy”  and thus restricted to the military sphere, it has become, under the influence of André Beaufre, the art of selecting from amongst “a whole gamut of means, both material and moral, ranging from nuclear bombardment to propaganda or a trade agreement” and, according to Beaufre, combining them in the pursuit of a sufficiently effective psychological result to produce a decisive moral effect.  Thus, all the different domains of war can be involved in strategy: alongside military strategy, General Beaufre introduces the concepts of economic, diplomatic, and political strategies, which are all subordinated to total strategy, which governs the conduct of total war. As a result, strategy is no longer confined to the domain of military operations, but is concerned rather with the conduct of the war as a whole and the multiplicity of means available.
55The expansion of the concept of war has profound consequences when it comes to defining the nature of war itself. In fact, if war encompasses the employment of all the means at the disposal of social groups, this can no longer be limited to the mere violent expression of the rivalry between organized groups. It is now necessary to conceive of war not as the geographically delimited confrontation of two armies, but rather as the name given to relations maintained by two groups, when they employ notably, but not exclusively, the specific means of armed violence. Such an approach makes it possible to see peace and war as two alternative forms of bilateral relations between social groups. This, we believe, is the central message of Clausewitz’s Formula: war and peace have a common nature—from which the idea of continuity is derived—and they are only distinguished by whether reciprocal violence is used or not—from which the idea of the addition of violence is derived. Raymond Aron has summed up this idea brilliantly, stating that war simply constitutes one of the phases of commerce between states, a phase that requires the [reciprocal] use of physical violence. “War does not suspend relations between states, rather it gives them a supplementary dimension—that of [mutual] violence”.  According to this approach, war and peace do not constitute general situations, or systemic states, but are applied to each of the interactions between organized groups. Hence, a social group is not simply “at war”, it is “at war with.”—and as a result, it can be logically both at war (with one group) and at peace (with another group).
56From these arguments, which Clausewitz did not formalize, but which can be deduced from the modified version of the Formula, emerges an important distinction between, on the one hand, war, and on the other, the violent confrontation of armies. War is the name given to the interaction of two organized groups which resort notably, but not exclusively, to violence against each other. The violent confrontation of armies is only the military dimension of that interaction. It is included in war, but war is the global, social, and political framework within which the violent confrontation of armies takes place. To put it more simply, one should think of war not as the violent confrontation itself, but as the context for that confrontation.
57* * *
58We have shown that the Formula constitutes one of Clausewitz’s most ambiguous contributions, in that it contains three different and contradictory definitions of war, which lead to war being conceived as a tool available to social groups, as the violent, geographically constrained interaction of two armies, and as one of the phases of relations adopted by organized groups. In order to overcome these ambiguities we have undertaken to elucidate the conception contained within the Formula. Firstly, we demonstrated that the conception of war as a political instrument is at odds with the importance accorded to the interactional dimension of war by Clausewitz; we then proposed that this conception was based in reality on a confusion between war, on the one hand, and armed violence, on the other. Secondly, we analyzed the nature of war interaction. Lastly, focusing principally on the reworded version of the Formula in Chapter Six of Book Eight, we advocated the idea that war does not mean the confrontation of two rival armies, but is one of the alternative phases of interaction between social groups. Thus we linked the three contradictory definitions of the Formula to three distinct concepts: armed violence, the violent confrontation of armies, and war.
59This distinction has an important implication with which we would like to conclude. It should lead us to rethink, or at least to clarify, our use of the expression “win a war”. This expression is generally used in two different ways. Firstly, it is used to describe the fact that an army has defeated its adversary militarily and has won a victory. It is also used to explain the success of one of the adversaries in achieving its political ends in the war. The expression “win the war”, therefore, is used to mean either military superiority within the context of the violent confrontation of armies, or the achievement of the political aims of one of the groups of combatants. It is thus related to the violent confrontation of armies, to violence, but not to war itself. So it seems to us that the current meanings of the expression “win the war” originate in confusion between the three notions which we have attempted to distinguish: violence, the violent confrontation of armies, and war. Hence, a further question should be raised: What would the expression “win the war” mean, if the definition of war that we have advocated is retained? Our reply is that one should probably cease using the expression. We have conceived of war as one of the forms of relations between organized groups, yet, while it is certainly possible to benefit from a relationship, to gain the upper hand in a relationship, or even end a relationship, it is impossible to win a relationship: one actor cannot win the relationship with another actor. Thus it must follow that war, just like peace, cannot be won. 
John Lewis Gaddis, The Long Peace: Inquiries into the History of the Cold War, New York, Oxford University Press, 1989.
John Mueller, Retreat from Doomsday: The Obsolescence of Major War, New York, Basic Books, 1989; Jean-Vincent Holeindre and Frédéric Ramel (eds), La fin des guerres majeures?, Paris, Economica, 2010.
Dario Battistella, Paix et guerres au xxie siècle, Auxerre, Sciences Humaines, 2011, 8. Note from Cadenza Academic Translations: Unless otherwise stated, all translations of foreign language material cited in this article are our own.
Steven Pinker, The Better Angels of Our Nature, New York, Viking, 2011; Joshua S. Goldstein, Winning the War on War: The Decline of Armed Conflict Worldwide, New York, Plume Reprint, 2012;
Human Security Research Group, Human Security Report 2013: The Decline in Global Violence. Evidence, Explanation, and Contestation, Vancouver, Human Security Press, 2013.
Pascal Vennesson, “Renaissante ou obsolète? La guerre aujourd’hui”, Revue française de science politique, 48(3-4), June-August 1998, 515-34.
Following the attacks in November 2015, President François Hollande began his speech to the Congress of the French Parliament in Versailles with the following words: “France is at war” (François Hollande, “Discours du président de la République devant le Parlement réuni en Congrès”, 16 November 2015).
Thierry Balzacq, Frédéric Charillon, Jean-Vincent Holeindre, Jean-Baptiste Jeangène Vilmer, Hugo Meijer, Alice Pannier, Frédéric Ramel, Jean-Jacques Roche, and Olivier Schmitt, “Penser la guerre”, Le Monde.fr, 27 November 2015, < http://www.lemonde.fr/idees/article/2015/11/27/penser-la-guerre_4819181_3232.html>.
Raymond Aron, Clausewitz: Philosopher of War, trans. Christine Booker and Norman Stone, New York, Simon & Schuster, 1986, 100.
Carl von Clausewitz, On War, ed. and trans. Michael Howard and Peter Paret, Princeton, Princeton University Press, 1984, 87. Translator’s note: The English translation of the German term politik, as employed by Clausewitz, varies from publication to publication, where it is rendered as either “policy” or “politics”. In order to retain Clausewitz’s original ambiguity, politik has been used throughout the article when referring to his conception of the term.
Éric Weil was the first person in France to advocate the “greatness of Clausewitz, the strategist and the political thinker” in a seminal article for the Revue française de science politiques (Éric Weil, “Guerre et politique selon Clausewitz”, Revue française de science politique, 5(2), April-June 1955, 291-314, on p. 293). Following him, Raymond Aron asserted in the preface to his work on Clausewitz, that On War constituted “a great work [...] of political philosophy” (Aron, Clausewitz, viii). Andreas Herberg-Rothe considered that Clausewitz had created a true “political theory of war” (Andreas Herberg-Rothe, Clausewitz’s Puzzle. The Political Theory of War, New York, Oxford University Press, 2007).
His doctoral thesis has been published: Benoît Durieux, Clausewitz en France: Deux siècles de réflexion sur la guerre (1807-2007), Paris, Economica, 2008.
Michel Dobry, “Clausewitz et “l’entre-deux”, ou de quelques difficultés d’une recherche de paternité légitime”, Revue française de sociologie, 17(4), 1976, 652-64; Emmanuel Terray, “Violence et calcul: Raymond Aron lecteur de Clausewitz”, Revue française de science politique, 36(2), April 1986, 248-68.
Weil, “Guerre et politique selon Clausewitz”.
André Glucksmann, Le discours de la guerre, Paris, L’Herne, 1967; Julien Freund, L’essence du politique, Paris, Dalloz, 2004, and “Guerre et politique: De Karl von Clausewitz à Raymond Aron”, Revue française de sociologie, 17(4), 1976, 643-51; Emmanuel Terray, Clausewitz, Paris, Fayard, 1999; René Girard, Achever Clausewitz. Entretiens avec Benoît Chantre, Paris, Carnets Nord, 2007.
Michel Dobry, “Lectures et lecteurs de Clausewitz”, cited in Durieux, Clausewitz en France, p. 624; Michel Dobry, Sociologie des crises politiques, Paris, Presses de Sciences Po, 2009, 1-5.
Numerous works have been published on Clausewitz and his thought in the English-speaking world in recent years, notably: Beatrice Heuser, Reading Clausewitz, London, Pimlico, 2002; Hugh Smith, On Clausewitz, Basingstoke, Palgrave Macmillan, 2004; Antulio J. Echevarria II, Clausewitz & Contemporary War, New York, Oxford University Press, 2007; Herberg-Rothe, Clausewitz’s Puzzle; Hew Strachan, Clausewitz’s On War. A Biography, New York, Atlantic Monthly Press, 2007; Hew Strachan and Andreas Herberg-Rothe (eds), Clausewitz in the Twenty-First Century, Oxford, Oxford University Press, 2007; Jon Tetsuro Sumida, Decoding Clausewitz: A New Approach to On War, Lawrence, University Press of Kansas, 2008; and Thomas Waldman, War, Clausewitz and the Trinity, Farnham, Ashgate, 2013.
Clausewitz, On War, 141.
Clausewitz, On War, 137.
Clausewitz, On War, 141.
Echevarria, Clausewitz & Contemporary War, 31.
Clausewitz, On War, 89.
Aron, Clausewitz, viii.
Robert E. Osgood, Limited War: The Challenge to American Security, Chicago, The University of Chicago Press, 1957; Bernard Brodie, War and Politics, London, Cassell, 1973; Aron, Clausewitz; Robert E. Osgood, Limited War Revisited, Boulder, Westview Press, 1979. For a critical point of view on the reception of Clausewitz, cf. Antulio J. Echevarria II, “On the Clausewitz of the Cold War”, Armed Forces & Society, 34(1), October 2007, 90-108.
For a study on the main authors who have “inverted” the Formula, cf. Jean-Vincent Holeindre, “Violence, guerre et politique: Étude sur le retournement de la “Formule” de Clausewitz”, Res Militaris, 1(3), Summer 2011, < http://resmilitaris.net/ressources/10144/29/res_militaris_violence_guerre_et_politique-jean-vincent_holeindre.pdf>.
The historians Martin Van Creveld and John Keegan have condemned the Formula respectively as a “modern invention” (Martin Van Creveld, The Transformation of War, New York, The Free Press, 1991, 126), and as
“incomplete, parochial and ultimately misleading”, which therefore has no universal validity (John Keegan, A History of Warfare, London, Hutchinson, 1993, 24). The two historians are very hard on Clausewitz, whom they see as out of date. They substitute their own visions of war, with the former seeing it as a continuation of sport and the latter as an expression of culture.
Clausewitz writes, “War is more than a true chameleon that slightly adapts its characteristics to the given case. As a total phenomenon its dominant tendencies always make war a paradoxical trinity–composed of primordial violence, hatred, and enmity, which are to be regarded as a blind natural force; of the play of chance and probability within which the creative spirit is free to roam; and of its element of subordination, as an instrument of policy, which makes it subject to reason alone” (Clausewitz, On War, 89).
The three-fold definition occupies a central place in the interpretation proposed recently by several authors, including: Echevarria, Clausewitz & Contemporary War; Herberg-Rothe, Clausewitz’s Puzzle; and Waldman, War, Clausewitz and the Trinity.
Aron, Clausewitz, 40.
Christopher Bassford, “Tip-Toe Through the Trinity”, The Clausewitz Homepage, April 2014, < https://www.clausewitz.com/mobile/trinity8.htm>.
Antulio J. Echevarria II notes that “Cold War interpretations of Clausewitz tended to use the term policy and politics interchangeably, though individual scholars naturally had their own preferences: Brodie preferred policy, and Osgood politics“. (Echevarria, “On the Clausewitz of the Cold War”, 94). The standard translation of Vom Kriege in English, by Michael Howard and Peter Paret, used to source the quotations in this article, prefers policy (Carl von Clausewitz, On War, Princeton, Princeton University Press, 1984, first edition 1976). Certain authors, including Christopher Bassford and Thomas Waldman, consider that the Formula refers to politics as both policy and politics (Christopher Bassford, “Clausewitz and his Works”, The Clausewitz Homepage, March 2016; Waldman, War, Clausewitz and the Trinity). Pascal Vennesson advocates the idea that Politik could also be understood as polity, and stresses the influence of organized groups and social structures and policies in war (Pascal Vennesson, “War Without the People”, in Hew Strachan and Sibylle Scheipers (eds), The Changing Character of War, Oxford, Oxford University Press, 2011, pp. 241-58).
Walter Bryce Gallie defines an “essentially contested concept” as one “whose proper use inevitably involves endless disputes about [its] proper [use]” (Walter Bryce Gallie, “Essentially Contested Concepts”, Proceedings of the Aristotelian Society: New Series, 56, 1955-56, 169). The criteria proposed by Gallie to determine whether a concept is contested or not have been debated and analyzed by David Collier, Fernando Daniel Hidalgo, and Andra Olivia Maciuceanu in “Essentially Contested Concepts: Debates and Applications”, Journal of Political Ideologies, 11(3), 2006, 211-46. Also Cf. John N. Gray, “On the Contestability of Social and Political Concepts”, Political Theory, 5, 1977, 331-48. To apply this notion to concepts similar to war, cf. David A. Baldwin, “The Concept of Security”, Review of International Studies, 23, 1997, 5-26; Willem de Haan, “Violence as an Essentially Contested Concept”, in Sophie Body-Gendrot and Pieter Spierenburg (eds), Violence in Europe: Historical and Contemporary Perspectives, Dordrecht, Springer, 2008, pp. 27-40.
Collier et al., “Essentially Contested Concepts: Debates and Applications”, 212.
The difficulties posed by the differentiated use of the same concept and the consequent importance of concept formation in social science has been the subject of numerous discussions following the seminal work of Walter Bryce Gallie (see note above) and Giovanni Sartori (in particular in Giovanni Sartori (ed.), Social Science Concepts: A Systematic Analysis, Beverly Hills, Sage, 1984). Sartori is in particular responsible for the notion of “conceptual stretching” and the “ladder of abstraction” (Giovanni Sartori, “Concept Misformation in Comparative Politics”, American Political Science Review, 64(4), 1970, 1033-53). Sartori’s contributions have been presented and discussed by: David Collier and James E. Mahon, Jr., “‘Stretching’ Revisited: Adapting Categories in Comparative Analysis”, American Political Science Review, 87(4), 1993, 845-55; Peter Mair, “Concepts and Concept Formation”, in Donatella della Porta and Michael Keating (eds), Approaches and Methodologies in the Social Sciences, Cambridge, Cambridge University Press, 2008, pp. 177-97. Cf. the equally important contribution of John Gerring: “What Makes a Concept Good? A Criterial Framework for Understanding Concept Formation in the Social Sciences”, Polity, 31(3), 1999, 357-93.
Clausewitz, On War, 88.
Clausewitz, On War, 607.
Aron, Clausewitz, 374-5.
Clausewitz, On War, 87.
Clausewitz, On War, 605.
Waldman, War, Clausewitz and the Trinity, 153.
Herbert Rosinski, “La structure de la stratégie militaire”, Stratégique, 2009, 20.
Battistella, Paix et guerres, 12.
Raymond Aron, Sur Clausewitz, Brussels, Complexe, 2005, 63.
Vincent Desportes, Comprendre la guerre, Paris, Economica, 2001, 14.
Clausewitz, On War, 87.
For a study on the choice of instruments of action, cf. Pierre Lascoumes and Patrick Le Galès, Gouverner par les instruments, Paris, Presses de Sciences Po, 2005.
Battistella, Paix et guerres, 12.
Dario Battistella, Théories des relations internationales, Paris, Presses de Sciences Po, 2009, 125
Clausewitz, On War, 75.
Alain Rey (ed.), Dictionnaire historique de la langue française, Paris, Le Robert, 1998, 1659.
Raymond Aron, Peace and War: A Theory of International Relations, New Brunswick, NJ, Transaction Publishers, 2003, 350.
Gaston Bouthoul, Traité de polémologie, Paris, Payot, 1991, 26.
Clausewitz, On War, 77.
Clausewitz, On War, 149.
Clausewitz, On War, ibid.
We will thus define peace in a negative manner, as the simple absence of war, contrary to the positive conception of peace advocated notably by Johan Galtung and the Journal of Peace Research (Johan Galtung, “Violence, Peace, and Peace Research”, Journal of Peace Research, 6(3), 1969, 167-91, and Peace by Peaceful Means: Peace and Conflict, Development and Civilization, London, Sage, 1996). The negative conception of peace is more faithful to the etymological origin of the word, which comes from the Latin “pax“, “pacis”, which refers to the “fact of making an agreement between two warring parties” (Rey, Dictionnaire historique, 2528).
It is useful here to specify that “use of violence” does not mean the effective use of violence, but rather the decision to resort to violence. Indeed, war is not one single long battle, but is instead a succession of episodes of the (bilateral and unilateral) effective use and non-use of violence. The discontinuous nature of violence in war therefore makes it impossible to define war using criteria related to the effectiveness of violence. As such, Thomas Hobbes proposed a definition of war using the criteria of the proven willingness of two adversaries to resort to violence (Thomas Hobbes, Leviathan, Peterborough, Ont., Broadview Press, 2002).
Clausewitz, On War.
Battistella, Paix et guerres, 12
Brodie, War and Politics, 2.
Thomas C. Schelling, Arms and Influence, New Haven, Yale University Press, 1966, 227.
The interactional nature of war is notably at the origin of one of the most important and most debated ideas of Clausewitz, which is developed in Chapter One of Book One: the idea of the escalation to extremes. Clausewitz identifies three reciprocal actions, which, when reasoning in the abstract, engage belligerents to resort to limitless violence and bring about the necessary escalation to extremes (Clausewitz, On War).
Raymond Aron, “Réponse au professeur Hepp”, Stratégique, 2009, 72.
Aron, Clausewitz, 295.
Benoît Durieux, Relire De la guerre de Clausewitz, Paris, Economica, 2005, 28.
Aron, Peace and War in International Relations, 23.
Amongst the main authors to have enunciated principles of war, one should highlight: Sun Tse, L’art de la guerre, Paris, Pocket, 1993; Nicolas Machiavel, L’art de la guerre, Paris, Flammarion, 1991; Antoine-Henri Jomini, Précis de l’art de la guerre, Paris, Perrin, 2001; Ferdinand Foch, Des principes de la guerre, Paris, Economica, 2007; John Frederick Charles Fuller, The Foundations of the Science of War, London, Hutchinson, 1926; Basil H. Liddell Hart, Strategy, New York, Praeger, 1967. Hervé Coutau-Bégarie provides a summary of them in his work Traité de stratégie, Paris, Economica, 1999.
Antulio J. Echevarria II, “Principles of War or Principles of Battle?”, in Anthony D. Mc Ivor (ed.), Rethinking the Principles of War, Annapolis, Naval Institute Press, 2005, pp. 58-78.
Clausewitz, “Stratégie”, in De la Révolution à la restauration. Écrits et lettres, Paris, Gallimard, 1976, p. 35.
Clausewitz, “Les principes essentiels de la conduite de la guerre en complément de mon enseignement auprès de son altesse royale, le prince héritier de Prusse”, in Clausewitz, De la Révolution à la restauration, p. 88
Clausewitz, “Les principes essentiels [...]”, pp. 88-9.
Clausewitz, On War, 128.
Clausewitz, On War, 95.
Clausewitz, On War, 605. The emphasis is our addition.
Clausewitz, On War, ibid.
It was not until 1827 that Clausewitz must have realized the importance of the political dimension of war, which must have led him to wish for his manuscript to be “thoroughly reworked”, as he writes in a note dated July 1827 (Clausewitz, On War, 69). In the same note he admitted that he was having difficulties in elucidating his ideas. It is thus possible that Clausewitz may have experienced a belated development in his ideas and that he had “never succeeded in entirely clarifying his own ideas” (Aron, Clausewitz, 6).
Aron, Clausewitz, 107
Aron, Clausewitz, ibid.
Hans Speier, “Ludendorff: The German Concept of Total War”, in Edward Mead Earle (ed.), Makers of Modern Strategy, Princeton, Princeton University Press, 1944, pp. 306-21.
André Beaufre, An Introduction to Strategy, New York, Praeger, 1965, 13.
Liddell Hart, Strategy, 335.
Beaufre, An Introduction to Strategy, 24.
Aron, Clausewitz, 381. The text in square brackets is our addition.
I would like to thank Gilles Bertrand, Sophie Panel, Éric Rouby, Cécile Vigour, and the anonymous reviewers of the Revue française de science politique for their comments and advice.