The Protection of Combatants from Unnecessary Suffering

Estimated reading time: 8 minutes

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I. Historical Roots and the Current Legal Basis

International humanitarian law primarily aims to limit the effects of armed conflicts on non-combatants. However, it also explicitly protects combatants from superfluous injury and unnecessary suffering. To understand how this protection applies, it is instructive to briefly recall the historical nascent of this objective.

The Lieber Code of 1863

As demonstrated in our discussion of military necessity, Article 16 of the Lieber Code stated that:

“Military necessity does not admit of cruelty– that is, the infliction of suffering for the sake of suffering or for revenge, nor of maiming or wounding except in fight, nor of torture to extort confessions.”

The Declaration of Saint Petersburg

In the preamble of the Saint Petersburg Declaration of 1868, the International Military Commission notably considered:

• “that the only legitimate object which States should endeavour to accomplish during war is to weaken the military forces of the enemy;

• that for this purpose it is sufficient to disable the greatest possible number of men;

• that this object would be exceeded by the employment of arms which uselessly aggravate the sufferings of disabled men, or render their death inevitable;

• that the employment of such arms would, therefore, be contrary to the laws of humanity”.

The Brussels Declaration

The Brussels Declaration of 1874, which remained unratified, picked up this consideration and specifically forbade

“the employment of arms, projectiles or material calculated to cause unnecessary suffering, as well as the use of projectiles prohibited by the Declaration of St. Petersburg of 1868”

The Hague Regulations

Article 23 (e) of the Hague Regulations (1907) also imposed the prohibition to employ “arms, projectiles or material calculated to cause unnecessary suffering”. Furthermore, the preamble to these regulations adopted the Martens Clause already discussed in our article on humanity in armed conflicts.

Additional Protocol I to the Geneva Conventions

Article 35 para. (2) of the 1977 Additional Protocol I (AP I) contains the most recent confirmation of this principle. It states that

“It is prohibited to employ weapons, projectiles and material and methods of warfare of a nature to cause superfluous injury or unnecessary suffering.”

Customary Humanitarian Law

Moreover, the International Committee of the Red Cross (ICRC) has adopted this principle as customary law. Rule 70 of the ICRC customary IHL database provides that:

“The use of means and methods of warfare which are of a nature to cause superfluous injury or unnecessary suffering is prohibited.”

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II.    Superfluous Injury and Unnecessary Suffering: By Nature or Design?

The difference between these two phrasings is not just semantic; it has significant legal consequences. The “calculated to cause” variant requires the intent to inflict injury or unnecessary suffering. If no such intent exists, the use of the weapon is legal. By contrast, the prohibition of means and methods “of a nature to cause” superfluous injury focuses on the objective effect. Consequently, the current wording of Article 35 (2) AP I is more restrictive as it prohibits weapons that are inherently excessive even if designers did not specifically intend to cause superfluous suffering.

The current understanding of the superfluous injury rule is heterogeneous, even among signatories of Additional Protocol I.

• The United Kingdom transcribed Article 35 (2) AP I verbatim into its Joint Service Manual.

• Section 4 of the German manual (“Kampfmittel und Kampfmethoden”) specifically mandates that: ‘it is in particular prohibited to use methods and means that are intended or likely to cause superfluous injury or unnecessary suffering”.

• The French Manual restricts these prohibitions to the primary and expected effects. This covers the weapon´s intended design or its performance in normal use, rather than incidental effects:  “…ces limitations et prohibitions s’appliquent aux effets principaux et attendus d’une arme, c’est-à-dire à ce pour quoi elle a été conçue ou auxquels on peut s’attendre en cas d’utilisation normale, et non aux effets fortuits et accidentels”.

• The U.S. DoD Law of War Manual (Section 6.6.2) uses a solely design-based standard for this rule. Section 6.6.2 posits: “The superfluous injury rule prohibits weapons that are designed to increase the injury or suffering of the persons attacked beyond that justified by military necessity.” This U.S. interpretation is narrower than the European manuals, as it suggests that the law only prohibits weapons specifically engineered for superfluous injury .

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III. When is Suffering “Unnecessary”?

State Practice and Proportionality

As Chapter 5 of the French manual observes, these notions are difficult to define precisely. Instead, their evaluation depends on their relationship to military necessity. Consistent state practice applies a proportionality test to this determination. This test assumes that IHL does not prohibit suffering that is the inevitable consequence of war, but only injuries and suffering that are excessive in relation to the military advantage pursued.

Section 402 of the German manual provides clear operational guidance. It provides that

“The use of methods or means of warfare results in superfluous injury or unnecessary suffering when the expected harm serves no military purpose, or when the effects of the weapons or projectiles cause injuries or suffering that are not required to neutralise opposing forces.”

Similarly, Section 6.6.3 of the U.S. DoD Law of War Manual states that:

“The test for whether a weapon is prohibited by the superfluous injury rule is whether the suffering caused by the weapon provides no military advantage or is otherwise clearly disproportionate to the military advantage reasonably expected from the use of the weapon.”

Unnecessary suffering in legal Literature and Case Law

LOAC literature also applies the proportionality test. Specifically, scholars emphasize that even terrible injuries do not per se make a weapon illegal. For instance, Gary D. Solis cites Yoram Dinstein who observed the fact that a weapon “causes “great” or even “horrendous” suffering or injury” does not per se make it illegal. (see Gary D. Solis, The Law of War” at 7.3, and Yoram Dinstein, The conduct of Hostilities under the Law of Armed Conflict at 59).

The case law of the International Court of Justice (ICJ) supports this view. The Court found in its Nuclear Weapons advisory opinion (para. 78) that:

“humanitarian law, at a very early stage, prohibited certain types of weapons either because of their indiscriminate effect on combatants and civilians or because of the unnecessary suffering caused to combatants, that is to say, a harm greater than that unavoidable to achieve legitimate military objectives.” (emphasis added).

From a military perspective, this interpretation is logical. Excessive force is inefficient, as it depletes military resources more rapidly than necessary to subdue enemy forces.

The Pursuit of a Medical Benchmark for unnecessary suffering

Humanitarian organizations have sought to establish a different approach. In 1996, the ICRC engaged in the “SIrUS Project,” which sought to quantify human suffering via objective criteria. The proposal suggested to determine superfluous injury by four criteria:

• Specific disease, abnormal physiological/psychological states, permanent disability, or disfigurement

• Field mortality >25% or hospital mortality >5%;

• Grade 3 wounds (Red Cross classification);

• Effects for which there is no proven treatment.

The project stated that it was “not anti-military,”. Still, its effects-based methodology faced stiff opposition from the U.S., Germany, the U.K., and other nations. Major Donna Marie Verchio condemned the project as “wholly inconsistent with the customary practices of nations” and flawed. Consequently, the ICRC no longer promotes it actively.

Recently, Jaroslav Krasny argued that

“the principle’s future (…) lies in its function as a humanitarian test: whether a weapon’s effects are medically indefensible regardless of military rationale.”

While this is a noteworthy contribution, it suggests that medical severity can entirely override military necessity. This effectively ignores the established IHL principle of proportionality. In the current threat landscape, characterized by aggression against democratic states, dismissing military necessity can be a risky proposition.

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IV. The Strategic Role of Emerging Disruptive Technologies (EDT) and AI for Avoiding Unnecessary Suffering

In this context, Emerging Disruptive Technologies (EDT) and Artificial Intelligence (AI) act as powerful tools for legal compliance. Traditional weapons often rely on “mass effects” that may cause incidental suffering to achieve a military objective. Conversely, AI-enabled precision systems allow for the “surgical” neutralization of threats. By enhancing accuracy and reducing the kinetic energy required to disable a target, AI can help military forces adhere to the St. Petersburg mandate: to disable the enemy while avoiding the “useless aggravation” of suffering. In modern maneuver warfare, these technologies ensure that the harm inflicted remains strictly necessary and proportionate.

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Conclusion

In summary, the protection of combatants from unnecessary suffering is not an absolute prohibition of harm, but a requirement for military efficiency and humanity. While humanitarian initiatives like the SIrUS Project have attempted to create objective medical benchmarks, state practice remains firmly rooted in the balancing of military necessity and proportionality. Looking forward, the integration of AI and EDT offers a promising path to reconcile these interests by allowing for more precise and, therefore, more humane military operations.

In our next blog post, we will explore the procedural safeguard that makes this possible: the Article 36 weapon review process.

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