On April 16, 2019, the annual seminar of the2035 Army Observatory was held on the theme: "What kind of army to fight tomorrow in high intensity? ». In his introductory remarks, the Chief of Staff of the French Army wondered about the very notion of "high intensity" (HI), even calling for a reflection on what this notion covers and the definition to be given to it.

Indeed, while strategic literature abounds to distinguish between "low intensity" conflicts and "real" warfare, military thinkers remain very discreet about "high intensity". Official doctrine is content with a rather vague definition that is open to interpretation and, while the specialist literature often mentions it, it does not explain it. Its characterization seems self-evident, belonging to the elementary military linguistic corpus, intuitive or obvious. For some, it is synonymous with "total war" and refers to Epinal's images of armoured divisions crossing the plains of Eastern Europe. For others, it is a special situation, a moment of exceptional violence that can occur in any theatre of operations.

HI therefore seems to take on more diverse and complex aspects than it might appear, depending to a large extent on the reference framework (legal or warlike) or the level of analysis (political, strategic or tactical) to which it is attached. At a time when a possible return to "high intensity" is more and more evoked [1], a precise definition of this notion and its implications seems necessary. Moreover, the exercise would not be insignificant: the choice of words could even be indicative of the ambition of armies to face future conflicts. The officially chosen meaning could well have important implications for military foresight, and even for the entire capability spectrum.

High intensity": a legal or a military concept?

High intensity refers to extremely different notions depending on the field (legal or military) to which it refers. While the legal profession has made this qualification very inclusive, so as to give the greatest number of people the benefit of a more protective law for the population, the military definition is no less ambiguous. It deliberately plays with possible interpretations and encompasses a very broad spectrum of situations. Intensity would therefore be, first and foremost, a matter of assessment.

Indeed, in the Law of Armed Conflict (LOAC) [2], as war between states is legally considered "total" in essence, the need to address the notion of intensity is not clear.Indeed, in the Law of Armed Conflict (LOAC) [2], since war between States is legally considered "total" in essence, the need to address the notion of intensity only became apparent with the discussions on non-international armed conflicts (NICAs), i.e. "prolonged confrontation(s) between government armed forces and non-governmental forces" [3] . 3] [3] Three criteria defining a "high-intensity" CANI were then used to delimit the scope of the Law. They relate essentially to the capabilities of non-state actors: to have a responsible command, to control a territory that allows them "to conduct continuous and concerted military operations " and to be able to apply IHL [4] . The legal qualification of intensity does not therefore relate to the volume of forces engaged, the quantity of destruction or the typology of weapons used, but rather to the capacity for action and mobilisation of all strategic resources on the part of the belligerents. The level of violence is only taken into account - although it is difficult to find precise criteria - to define whether there is a situation of armed conflict (and therefore of application of IHL) or only internal disturbances, which are then subject to the internal legislation of the State concerned. 5] In sum, according to the legal understanding, all inter-State conflicts would by definition be of high intensity, and many existing asymmetric conflicts could be considered as such.

However, the military view of high intensity is not unambiguous either. French doctrine defines it as "an operation in which all operational functions are activated to oppose the adversary's characterized violence" [6] . 6] Perhaps voluntarily, almost every word in this sentence is subject to interpretation. An "operation" initially refers to an entire campaign in a given theatre [7] (e.g., Operations Harmattan or Barkhane), which begins with entry first and ends with the withdrawal of the engaged force. It characterizes the operational level. However, the same word is used when referring to "operations", i.e. a "series of coordinated actions with a defined goal " at the tactical level [8] . The rest of the definition does not help to dispel the semantic vagueness. The criterion of integrating all operational functions is inept today: this principle being, down to the lowest levels, one of the characteristics of modern combat. Finally, the notion of "characterized violence" is completely subjective in the absence of precise criteria. Thus, even according to the military definition, "high intensity" could concern a multinational expeditionary force as well as a leader of a joint battle group, facing a symmetrical enemy such as a handful of terrorists.
Whether from a legal or military point of view, no definition seems precise enough to delimit the contours of HI. A large inclusive vagueness, perhaps deliberately maintained, finally makes it possible to integrate almost any military action into it.

1] "The likelihood of a confrontation [with state actors] is reinforced by the increased strategic competition of power states and the resulting risks of escalation. More symmetrical and tougher, such a prospect requires modern combat capabilities capable of integrating into high-intensity operations". Revue stratégique de défense et de sécurité nationale, DICOD, Ministry of the Armed Forces, October 2017.

2] Or international humanitarian law (IHL).

3] Purpose of the Second Protocol Additional to Article 3 common to the Geneva Conventions of 1949, to be found at https://www.icrc.org/fr/guerre-et-droit/traites-et-droit-coutumier/conventions-de-geneve, accessed 2 May 2019.

4] Original texts and commentaries to be found at https://ihl-databases.icrc.org/applic/ihl/dih.nsf/Comment.xsp?documen-tId=26144B48AA09DF15C12563BD002DF215&action=OpenDocument, accessed 3 May 2019.

5] The jurisprudence of the International Criminal Tribunal for the former Yugoslavia (ICTY) takes into consideration a multitude of indicators (the use of the army, the length of time spent in detention, the number of days in detention, the number of persons in detention, etc.).5] The case law of the International Criminal Tribunal for the former Yugoslavia (ICTY) takes into consideration a multitude of indicators (the use of the army, the duration of the conflict, the frequency of acts of violence and military operations, the nature of the weapons, the displacement of civilian populations, the territorial control exercised by the opposition forces, the number of victims, etc.).). Sylvain Vité, Typology of armed conflict in international humanitarian law: legal concepts and realities, International Review of the Red Cross, 873, 2009 available at https://www.icrc.org/fr/doc/resources/documents/article/review/review-873-p69.htm.

6] DC-004, Joint Glossary of Operational Terminology, Joint Command of Concepts, Doctrines and Experiments, Ministry of Defence, December 2013, amended June 2015.

7] "An organized set of actions carried out by a generally joint, or even combined or multinational, force in one or more fields of operation with a view to achieving one or more military objectives. "EMP 60.641, Glossaire de l'armée de Terre, CDEF, Ministry of Defence, 2013, p. 346.

8] DC-004, op. cit . p.102.