This doctoral thesis, now published as a monograph, provides a thorough analysis of one of the most crucial concepts of the modern law of armed conflicts (LOAC), namely military objectives. The concept is crucial because the targeting of such objectives is directly linked to the principle of distinction, which in turn is a cardinal tenet of LOAC. It requires that the belligerents must always make the distinction between civilian objects and persons on the one hand, and military objectives (persons and objects) on the other, and attack only the latter to the exclusion of the former (Article 48 of the Additional Protocol I of 1977 (AP I)). Thus, the concept of military objectives is cast amidst the protection of civilians during the conduct of hostilities (whereas Geneva Convention IV of 1949 concerns their protection outside the context of combat action). It stands to reason that this protection is an essential part of the modern law of armed conflicts. Moreover, it is only superficially surprising that AP I was the first treaty to generally define military objectives. In the nineteenth century, the civilian hardly appeared in the LOAC. It was at that time simply taken for granted that civilians were outside the reach of military action; they would not participate in it and concomitantly would be spared from attacks. The social environment of the past was such that military action and civilian presence were reasonably distinct: the battlefield was the pitch for military action, other areas were bluntly aloof from such action. The twentieth century completely changed these parameters. Air power allowed a belligerent to wreak heavy havoc into all the lands of the adverse party. Industrialization and modernization of the army made civilian objectives relevant from a military standpoint, in particular industrial plants. Finally, the difference between civilians and military personnel was blurred, since civilians participated in a variety of forms to military operations (guerilla warfare is but one of the most emblematic forms of such participation). All these factors, among others, explain that the majority of victims in modern armed conflicts are civilians, not rarely up to a proportion of 90 per cent.1 The question of military objectives remains also highly relevant when viewed from another perspective. It is a concept often applied in modern military campaigns, where air power is of the essence. However, it gives rise to uncertainties at least on two accounts. First, the definition is open-ended and contextual; it must be operationalized in single cases and this gives rise to legal uncertainty. Indeed, Article 52, § 2, AP I, the cardinal provision in this regard, provides only for criteria which have to be applied by the belligerent to single sets of facts in order to determine if an object is a military objective. Second, there are marked differences of interpretation between the US and the continental European conceptions of military objectives, especially in certain areas of targeting such as ‘economic targets’ (i.e. targets chosen for their economic value to the war-sustaining effort). Notwithstanding the relevance of the concept of military objectives, there is hardly a wealth of monographic treatment of the subject matter. Indeed, no monograph in the English language was directly and exclusively devoted to that notion before the present publication. This new monograph is thus more than welcome.