Cardinal Principles of International Humanitarian Law


International humanitarian law aims to impose limits on the destruction and distress caused by armed conflict. The law of armed conflict is essentially a compromise between two fundamental principles, of humanity and of military necessity.1Larissa Fast, Unpacking the principle of humanity: Tensions and implications <> The principle of military necessity permits force required to achieve the legitimate purpose of a conflict, and the principle of humanity forbids the infliction of all suffering, injury or destruction not necessary for achieving the legitimate purpose of a conflict.2Article 35(2), International Committee of the Red Cross (ICRC), Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977, 1125 UNTS 3 All other rules of international humanitarian law (IHL) are constructed on these principles.

This article shall explore any controversies in the construction of principles of IHL, and shed light on their application in contemporary conflicts. The International Court of Justice has held in the Nuclear Weapons Advisory Opinion that “a great many rules of humanitarian law applicable in armed conflict are so fundamental to the respect of the human person and ‘elementary considerations of humanity’…”, that they are “to be observed by all States whether or not they have ratified the conventions that contain them, because they constitute intransgressible principles of international customary law”.3Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports 1996, p. 226, International Court of Justice (ICJ), 8 July 1996, 257, para.79 However, these principles have been criticized as being dense, overly technical, and indeterminate, leading to a complexity which hinders their effective implementation and enhances the danger of non-compliance with IHL in the field.4Kaye, David A., Complexity in the Law of War. Progress in International Organization, 2007

Kaye argues that there is complexity in IHL principles which render it, problematically, a ‘lawyers’ law, given that “key provisions of the law of war have become difficult to interpret, frequently undermined by an inability to find consensus on the meaning of important provisions”.5ibid He argues that unambiguous and realistic legal rules best serve those who are supposed to apply them and instead this ambiguity and lack of clarity means that it is difficult to implement without legal advice. These criticisms will be explored in this article in relation to the cardinal principles of IHL.

Principles of Humanity

At the Hague Peace Conference of 1899, a Russian diplomat, Fyodor Fyodorovich Martens, successfully introduced the “Marten’s clause” into the preamble of the Hague Convention II, from which the principle of humanity is derived.6Hague Convention No. II of 1899 and Hague Convention No. IV of 1907. Convention [No. II] with Respect to the Laws and Customs of War on Land, with annex of regulations,July 29, 1899, 32 Stat. 1803, 1 Bevans 247 It reads, “the inhabitants and the belligerents remain under the protection and the rule of the principles of the law of nations, as they result from the usages established among civilized peoples, from the laws of humanity and the dictates of public conscience.”7Rupert Ticehurst, The Martens Clause and the Laws of Armed Conflict < >

Rupert Ticehurst has argued that this principle is ambiguous, and so is denied a place in legal dialogue as a powerful influence on international law.8Robin Coupland, Humanity: What is it and how does it influence international law? < > As a result, the widest interpretation of the Martens clause is that conduct in armed conflicts is not only judged according to treaties and custom but also to the principles of international law referred to by the Clause.9Ibid 3 In other words, in cases not covered by IHL treaties, the conduct of belligerents remains regulated at a minimum by the principles of the law of nations, the laws of humanity, and the dictates of public conscience.

However, the issue remains that these terms are very vague, not least that of ‘public conscience’. For instance, public conscience may be startled by selective cases of humanity, in which some are included, and others are excluded from our notions of humanity. Indeed, war itself requires an appeal to exclusive humanity for one party to the conflict and the dehumanisation of the other side in order to enable violence.10Larissa Fast, Unpacking the principle of humanity: Tensions and implications < >

In other words, the objective nature of the principle of humanity is questionable since the public conscience of armed parties might dictate and posit its humanity differently. Despite multiple interpretations of the principle of humanity, Jean Pictet has asserted that “the principle of humanity stands out on its own in the doctrine of the Red Cross, and all other principles hang from it.” As a principle, humanity implies an inherent worth and dignity of the person, which is preserved collectively by all principles of IHL.11Ibid 5 While important, its normative ambiguity undermines its significance and effectiveness in actually curtailing inhumane treatment on the battlefield.12Meron, T. (2000). The Martens Clause, Principles of Humanity, and Dictates of Public Conscience. The American Journal of International Law, 94(1), 78. page 88 The U.S. Department of the Army has also stated that “such broad phrases in international law are in reality a reliance upon moral law and public opinion.”13Ibid As a result, such broad principles are difficult to render into hard binding law. The principle of humanity therefore may be better pushed through reliance on other principles of IHL to which we now turn. 

Principle of Distinction

The parties to a conflict must at all times distinguish between civilians and combatants in order to spare the civilian population and civilian property. Attacks may be made solely against military objectives.14Article 48, Additional Protocol I Military objectives are limited to those objects which by their nature, location, purpose or use make an effective contribution to military action and offer a definite military advantage.15Article 52(2), Additional Protocol I; Scope of Military Objectives and Modern Warfare < > This definition leaves a lot to be desired given its abstract nature and the ICRC has even conceded that it is indeterminate.16Kaye (supra n. 4) It is unclear what an effective contribution to military action involves. Moreover, some argue that it includes war-sustaining capabilities which allow for economic targets to also be legitimate military objectives.17Ibid Others narrow the definition down to only including war-making functions which bring about a direct military advantage.18Ibid

Targeting of dual-use objectives, or objectives that can be used for both military and civilian application, demonstrates the vagueness of the definition of military objectives.19Laurent Gisel, “The Principle Of Proportionality In The Rules Governing The Conduct Of Hostilities Under International Humanitarian Law” < › download › file › 4358_002_ > Under the definition of military objectives, a dual-use object can be a legitimate military target if it makes an ‘effective contribution to military action’ and its destruction offers ‘a definite military advantage’.20Ibid 9 The lawfulness of some targets is debated. For instance, during the war between Israel and Hezbollah in Lebanon in 2006, it was questionable whether Beirut airport was a military target because it was used to bring in supplies and weapons from neighbouring countries. Moreover, whether a power station could constitute a military objective as it contributes to a party to the conflict’s effectiveness is also contested.  For example, the targeting of al-Jalaa Tower in Gaza may not be a legitimate military objective as a media facility. Even if it was used as a tool of propaganda by Hamas, it may not be justified to attack a civilian use facility, and such conflicts have to be judged on a case-by-case basis.21Ibid 9 Michael Schmitt suggests the answer depends on the extent to which the attacker used information to confirm the nature of the target and selected weapons and tactic designed to avoid causing harm to civilians and civilian objects, but he also admits that there are cases where it is impossible to verify that individual facilities on an installation are military objectives.22Ibid 9

At the same time, it is important to recognise that conflict zones today, witness an unparalleled intermingling of civilians and armed groups. It is argued by the defence counsel in Galic before the ICTY that the presence of some 40,000 Bosnian Muslim troops spread throughout the area under attack rendered the entire area, where civilians were killed by the shelling campaign, a military objective.23Ibid 9 The fact that conflicts occur more frequently in areas where there is increased intermingling makes it a difficult process to determine military objectives.

Principle of Proportionality

The principle of proportionality seeks to limit damage caused by military operations by requiring that the effects of the means and methods of warfare used must not be disproportionate to the military advantage sought.24ICRC, Proportionality < > However, the textual formulation of this principle is problematic as it is imprecise and indeterminate.25Clarke, Ben. “Proportionality in Armed Conflicts: A Principle in Need of Clarification.” Journal of International Humanitarian Legal Studies, vol. 3, no. 1, 2012, p. 73-123. p.73 It prohibits attacks against military objectives which are “expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated”.26Article 51(5)(b), Additional Protocol I Violating the rule of proportionality renders the attack indiscriminate.

However, it is important to realise that determining whether the loss is proportionate to the resulting military advantage is not so straightforward due to its subjective interpretation.  The question ultimately is “How do you assess the value of innocent human lives as opposed to capturing or destroying a particular military objective?”27W. Fenrick, ‘Applying IHL Targeting Rules to Practical Situations: Proportionality and Military Objective, 27 Windsor YB. AccessJust. 271 (2009) Clarke puts it aptly when he asks whether proportionality is “like beauty, too subjective to be taken seriously?”28Clarke (supra n. 25) p.73 It requires comparing the anticipated military advantages with anticipated civilian losses or injury, rather than looking at actual advantage or actual civilian losses or injury.29Ibid This allows a margin of appreciation for military commanders, however, the term “may be expected” incorporates an aspect of objective reasonableness, in that the military commander should act as a reasonable person would with the information at the time.30Ibid Where civilian losses or harm would be deemed excessive, the military commander is expected to call off the attack or he or she would incur individual responsibility for war crimes. However, it remains clear how certain commanders are to be that the resultant civilian loss or injury is to be excessive, another problem with the overall subjectivity of the principle’s formulation, and one that works in the favour of the military to the detriment of civilians.31Ibid Most importantly, it results in proportionality as a principle losing its normative force owing to the lack of operational clarity and its inability to guide decision makers.32Dill, Applying the Principle of Proportionality in Combat Operations, Policy Briefing December 2010, University of Oxford

This calculation is also harder to make  for ‘emerging’ targets as opposed to preselected ones for which there is time to ensure compliance with the principle of proportionality through advance planning and information collection.33Clarke (supra n.25) However, for emerging targets it is difficult to plan in advance at such short notice and therefore, an accelerated analysis on proportionality is required. In the Iraq war of 2003, it was noted that “where insufficient time was available to carry out precise assessments, the result was often disproportionate bombing”.34Ibid

Another question is what constitutes ‘excessive’ force? In clarification, ICRC’s commentary on Article 51(5) of 1977 Additional Protocol I states, “Of course, the disproportion between losses and damages caused and the military advantages anticipated raises a delicate problem; in some situations there will be no room for doubt, while in other situations there may be reason for hesitation. In such situations the interests of the civilian population should prevail…”.35Claude Pilloud, Yves Sandoz, Christophe Swinarski, Bruno Zimmermann, Commentary on the Additional Protocols: of 8 June 1977 to the Geneva Conventions of 12 August 1949, Martinus Nijhoff Publishers, 1987,  page 626; Proportionality in attacks (under IHL) < > Although the interest of civilians is a subjective question, it is clear that IHL aims to preserve the wellbeing of civilians and non-combatants in armed conflicts.

An example of how difficult it is to gauge proportionality is indicated by the targeting of ISIL fighters in Syria. On 4 October in Aleppo Governorate, ISIL fighters were targeted killing up to 25 people. Multiple sources reported that up to 13 of those killed were civilians, including nine children while only between two and four ISIL fighters were killed.36ICRC, “Syria, Report by UN Commission of Inquiry (March 2017)” < > If 13 civilians were killed and only between two and four ISIL fighters, does this indicate that the proportionality principle was violated? Local sources also reported that ISIL fighters had forced citizens to gather to watch the implementation of a punishment when the airstrike occurred.37Ibid 26 It is difficult to argue whether or not the loss of civilian lives was proportionate to the military advantage of weakening ISIL’s stranglehold. Again, conflicts have to be analysed on a case-by-case basis due to ambiguity in defining what constitutes as disproportionate. This is not an easy calculation and the definition leads to more questions than it answers. 

Principle of Precaution

Even if from the abovementioned example, a party to the conflict’s attack on civilians was proportionate to the military advantage of weakening the opposing armed group, should it have taken more precautions in minimising harm to civilians? The precautionary principle requires taking feasible measures to ensure that civilians or civilian objects are not being attacked.38Article 57, Additional Protocol I It requires the taking of precautions in choosing weapons and tactics to minimise incidental injury and collateral damage and the selecting of military objectives among those giving similar military advantage expected to cause least danger to civilian lives or objects.39Ibid It obliges those responsible to ascertain that objectives are military and not civilian and to cancel the attack in the event that it is civilian, or give a warning, if possible, if the attack may affect civilians.40Kaye (supra n 4) However, the obligation is to ‘everything feasible’ to ‘verify’ targets are in fact military objectives. Something which may be very difficult to determine and it may further be unclear when it is apparent that a target is not military and the attack should be called off.

For instance, the recent destruction of a tower in Gaza which hosted Associated Press and Al-Jazeera arguably did not comply with the precautionary principle. The building was targeted on the grounds that it was also used by Hamas’s military intelligence, however, it is unclear whether it was a legitimate military objective given that it contained press groups and journalists.41Gross, The 2021 Gaza War and the Limits of International Humanitarian Law < >  In its defence, the attacking party has argued that the journalists were warned that an attack was coming and given an hour to get out before the tower was destroyed.42Ibid 30 It is unclear if this was sufficient demonstration of precaution because Hamas members had left with their equipment before the airstrike.43Adil Ahmad Haque, The IDF’s Unlawful Attack on Al Jalaa Tower < > There was no military objective left behind, and so the military advantage anticipated from the attack is questionable. Moreover, the notion that abiding by the precautionary principle would render an otherwise unlawful attack lawful is also a worrying argument that it is hoped states will not follow. 


While the principles of IHL form a powerful regulatory force for conduct in modern conflicts, there are issues with their application owing to their complexity and indeterminacy. It is arguable that they fall short in creating more precise rules of warfare so that states and armed groups cannot escape liability for violating them. While the principles are important rules of war which endeavour to reduce human suffering and protect those most vulnerable in an armed conflict, they also leave a lot to be desired. This is particularly so because ambiguous rules which are difficult to interpret and apply to real-life scenarios are frequently undermined. A lawyers’ law, as Kayes puts it, is hard to implement by not only armed groups but even advanced armies who then focus on circumventing or moulding them to fit their own ends. It is hoped that further clarity is brought to these principles in order to better ensure and enhance compliance.

The opinions expressed in the articles on the Diplomacy, Law & Policy (DLP) Forum are those of the authors. They do not purport to reflect the opinions or views of the DLP Forum, its editorial team, or its affiliated organizations. Moreover, the articles are based upon information the authors consider reliable, but neither the DLP Forum nor its affiliates warrant its completeness or accuracy, and it should not be relied upon as such.

The DLP Forum hereby disclaims any and all liability to any party for any direct, indirect, implied, punitive, special, incidental or other consequential damages arising directly or indirectly from any use of its content, which is provided as is, and without warranties.

The articles may contain links to other websites or content belonging to or originating from third parties or links to websites and features in banners or other advertising. Such external links are not investigated, monitored, or checked for accuracy, adequacy, validity, reliability, availability or completeness by us and we do not warrant, endorse, guarantee, or assume responsibility for the accuracy or reliability of this information.

Similar Posts