In the previous article in this series on select principles of international humanitarian law (“IHL”, also referred to as “the law of armed conflict” or “LOAC”), we discussed military necessity and humanity as two interdependent principles that commanders and decision-makers must balance. In this article, we examine fundamental questions on humanity to clarify its meaning, legal nature and function in international humanitarian law. Readers wishing to explore specific aspects of humanity in armed conflicts beyond this article can do so by reading the sources highlighted in the discussion of each question.
Estimated reading time: 8 minutes
I. What is the Martens Clause and why is it instrumental for humanity in armed conflicts?
Historical origin of the Martens Clause
The Russian diplomat Fyodorov Fyodorovich Martens suggested the so-called Martens Clause to break a stalemate in negotiations. The stalemate arose during negotiations of the1899 Hague Convention II “Laws and Customs of War on Land”. Delegates of the participating states then adopted the clause in the Convention’s preamble and formulated it as follows:
“Until a more complete code of the laws of war is issued, the High Contracting Parties think it right to declare that in cases not included in the Regulations adopted by them, populations and belligerents remain under the protection and empire of the principles of international law, as they result from the usages established between civilized nations, from the laws of humanity and the requirements of the public conscience.” (emphasis added)
To this day, the Martens Clause has not lost its relevance for humanity in armed conflicts. The ICRC, Scholars and practitioners have progressively attributed a wider meaning to it.
Expansion of the Martens Clause by the International Committee of the Red Cross
In 1987, the ICRC Commentary on the Additional Protocol one to the Geneva Conventions of 1949 (AP I) suggested that
“the Martens clause prevents the assumption that anything which is not explicitly prohibited by the relevant treaties is therefore permitted.”
This view has not stirred up much controversy. However, more expansive interpretations of the Martens Clause and the notion of humanity have generated greater debate. Before addressing their legal character in Section III., we first clarify the operational meaning of humanity.
II. What does “humanity” stand for in armed conflicts?
The general public knows the notion of ‘humanity’ mainly from war crimes prosecutions under the Rome Statute. These prosecutions take place before the International Criminal Court (ICC). More recently, the United Nations started preparatory talks on a new international treaty on crimes against humanity
This article instead examines humanity through international humanitarian law. The concept of humanity was not new when it appeared in the Martens Clause. The Declaration of Saint Petersburg had already referred to it in 1868. According to the Declaration, the International Military Commission assembled in Saint Petersburg
“fixed the technical limits at which the necessities of war ought to yield to the requirements of humanity” and found that the laws of humanity would be violated by “the employment of arms which uselessly aggravate the sufferings of disabled men, or render their death inevitable.” (emphasis added)
Article 35 para. 2 AP I expressed this limitation in the basic rule that prohibits parties to the conflict
“to employ weapons, projectiles and material and methods of warfare of a nature to cause superfluous injury or unnecessary suffering.”
III. Is “humanity” an independent legal principle?
The Martens Clause expressly referred to ‘the laws of humanity.’ However, the legal nature of humanity in armed conflicts remains controversial to this day. Importantly, this controversy is not merely academic. It also influences military operations and public discourse on the use of force justified by military necessity.
Some authors question the role of humanity as an independent legal principle of international humanitarian law. They also argue that commanders must not treat humanity as a requirement of the law of armed conflict. For further discussion see Gary D. Solis, The Law of Armed Conflict, Third Edition, 7.5 Humanity: A Core Principle?” with further citations.
Other authors instead regard humanity as a “fundamental principle of the law of armed conflict.” See Geoffrey S Corn, Max-Planck Encyclopedia of International Law (IMPL).
Still other authors describe humanity as a “formative principle of IHL”. They argue that it can function as an independent source of legal obligations during armed conflict in some situations. See Jereoen van den Boogaard, Proportionality in international humanitarian law, Principle, Rule and Practice, chapter 3, p. 63.
Diverging doctrinal interpretations
Article 1 para. 2 AP I also recognizes the Martens Clause and humanity in international armed conflicts as “general principles”. It provides that
“In cases not covered by this Protocol or by other international agreements, civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience.” (emphasis added)
Scholars often describe developments in IHL as “the trend towards the humanisation of armed conflict”. However, compliance with humanitarian principles remains uneven in practice. Denying humanity’s role as a principle of humanitarian law has nevertheless become increasingly difficult.
But has the principle of humanity acquired the status of a general principle that requires no confirming state practice? This question remains contested. Readers seeking deeper analysis may consult the contributions of Mika Hayashi and Robert Ticehurst. Their work also guides readers to further sources.
In the next section, we show how several law of war manuals and rules of engagement have addressed the principle of humanity. Together, they show how the principle shapes modern warfare.
IV. How do Current Law of war Manuals and ROE operationally implement the Principle of Humanity?
Law of War manuals explain and interpret the international legal rules governing armed conflict for military personnel. Rules of engagement (ROE) complement these manuals. They determine the circumstances and limitations governing the deployment of armed forces, and often appear in mission-specific formats. The San Remo Handbook of Rules of Engagement provides a non-binding reference for rules of engagement usable by any nation. By contrast, national ROE provide guidance for the armed forces of the states that issue them.
Accordingly, manuals and ROE widely acknowledge the principle of humanity and translate it into operational guidance.
Implementation in national ROE and Law of War Manuals
For instance, the United Kingdom Manual of National Rules of Engagement addresses the principle of humanity in Section 10. That section governs the use of force within armed conflict and operations as follows:
“The concept of humanity forbids the infliction of suffering, injury or destruction not actually necessary for the accomplishment of legitimate military purposes. The principle of humanity is based on the notion that once a military objective has been achieved, the further infliction of suffering is unnecessary. Thus, if an enemy combatant has been put out of action by being wounded or captured, there is no military purpose to be achieved by continuing to attack him. For the same reason, the principle of humanity confirms the basic immunity of civilian populations and civilian objects from attack because civilians and civilian objects make no contribution to military action.”
The U.S. DoD Law of War Manual refers to this guidance and defines the principle of humanity as
“the principle that forbids the infliction of suffering, injury or destruction unnecessary to accomplish a legitimate purpose.”
The Military Manual on international law relevant to Danish armed forces in international operations concurs with this definition. It identifies several aspects of the principle of humanity, i.e.
- the obligation of belligerents to limit their use of means and methods of warfare
- the requirement to take precautions during the planning and execution of attacks and
- the requirement o take such precautions when defending against attacks, and
- adherence to a minimum standard of humane treatment for any person a belligerent State holds in its custody.
The current version of the German Law of Armed Conflict Manual also recognizes the humanitarian imperative in Section 141.
V. How does humanity in armed conflict impact military necessity?
Although many authors have written about balancing military necessity and humanity, concise guidance again appears in the U.S. DoD Law of War Manual which states in Section 2.3.1.1 that
“Humanity may be viewed as the logical inverse of the principle of military necessity. If certain necessary actions are justified, then certain unnecessary actions are prohibited. The principle of humanity is an example of how the concept of necessity can function as a limitation as well as a justification. Because humanity forbids those actions that are unnecessary, the principle of humanity is not in tension with military effectiveness, but instead reinforces military effectiveness.”
Moreover, readers seeking further analysis can consult our previous article on military necessity. They may also review the observations of Michael N. Schmitt.
Conclusion
Debate on the scope of the Martens Clause remains unsettled. Debate also continues on the nature of the principle of humanity in armed conflicts. Nevertheless, this article demonstrates several key findings. First, the Martens Clause continues to provide an interpretive safeguard where treaty law remains silent. Second, the humanitarian prohibition of unnecessary suffering has become firmly embedded in treaty law and military doctrine. Third, despite ongoing doctrinal debates, operational manuals and rules of engagement show that humanity already guides real-world military decision-making of democratic states.
Recent and ongoing armed conflicts show that balancing military necessity and humanity remains challenging in practice. The rise of artificial intelligence in the military domain now raises new questions about accountability and human control. Both issues remain closely linked to humanitarian needs. However, new means of warfare are not challenging IHL for the first time.
In its Advisory Opinion on Nuclear Weapons the ICJ concluded that the Martens Clause
“has proved to be an effective means of addressing the rapid evolution of military technology”.
Against this background, introducing new rules for every emerging technology is not sensible. This holds true even for technologies as significant as artificial intelligence. IHL has stood the test of time and will likely continue to do so in the foreseeable future.
Looking ahead: preserving humanity in future warfare
Looking ahead, preserving humanity in warfare is not an unattainable ideal. Armed forces, governments, and defence industries can meet this operational challenge through disciplined doctrine and responsible technological development. They must also rely on legally informed decision-making.
Modern warfare will continue to evolve, but the humanitarian principles guiding it are adaptable enough to evolve as well.
If you would like to discuss particular aspects of designing military AI systems for IHL compliance or if you have any questions on specific LOAC principles, get in touch with me by email or just give me a call.