Lieber Studies Series – Military Investigations

Editors’ note: This post is based on the author’s chapter in Civilian Protection in Armed Conflict: Select Issues (Jelena Pejic and Margaret Kotlik eds. 2025), the eleventh volume of the Lieber Studies Series published with Oxford University Press.

Military investigations form an essential element of civilian protection during armed conflict. When a belligerent causes civilian deaths, injury, or damage, an investigation is necessary to identify the causes of that harm, learn lessons for the future, and assess whether the incident involved any violation of the law of armed conflict (LOAC). Normally, it falls to the armed forces of the party that caused the harm to conduct the initial investigation.

Yet military investigations during armed conflict present significant challenges. First, the involvement of the armed forces raises concerns regarding the effectiveness of the investigation, particularly its independence and impartiality. Second, the requirement to investigate may divert scarce resources away from the military mission. Third, any investigation might face significant hurdles due to the ongoing armed conflict. For instance, the location of the incident might be behind enemy lines, witnesses might have fled or be unwilling to cooperate, and the armed forces might lack the requisite personnel or expertise to investigate effectively.

My chapter in the Lieber Studies volume Civilian Protection in Armed Conflict: Select Issues considers how States can strike a proper balance between the requirement to conduct an effective investigation and the military necessity to achieve the mission. It assesses not only States’ investigative duties under LOAC but also their obligations under international human rights law (IHRL) and the Rome Statute of the International Criminal Court (ICC). In practice, for those States that are party to the Rome Statute or to certain regional human rights treaties, it is these latter bodies of law that impose the highest investigatory burden.

This post addresses first the standards that armed forces’ investigations must satisfy. It then outlines some of the chapter’s conclusions regarding how States might balance compliance with the requisite investigatory standards against military considerations, including the need to accomplish the mission.

Investigatory Standards

LOAC does not stipulate the standards that armed forces’ investigations into potential violations must meet, either in treaty texts or in customary international law. Nevertheless, it is clear by implication that such investigations must be effective, in the sense that they must be capable of enabling a determination of whether LOAC has been violated and if so, the causes and the perpetrators of that violation (paras. 30-32).

The specific steps that a State must take to fulfil this obligation are highly context dependent. Factors such as ongoing hostilities, the availability of witnesses, and the number of incidents to investigate will influence the depth of the investigation a State is able to undertake, as well as its robustness (p. 79-82). From a pure LOAC perspective, a State will comply with its investigative obligations provided it acts reasonably and with due diligence, in light of the circumstances ruling at the time. Thus, a more detailed investigation may be required regarding grave allegations, when the armed forces are in control of the relevant location, than in respect of less serious allegations arising in the context of active hostilities.

When IHRL applies to situations of armed conflict, it imposes far more demanding investigative standards. The difference is particularly striking when considering the principles of independence and impartiality. LOAC imposes no requirement on States for investigations into civilian harm to be conducted outside the chain of command. Indeed, Additional Protocol I stipulates that it is the commander who bears the primary responsibility to initiate an investigation and, if appropriate, to take action against the perpetrators and report the matter to the competent authorities (art. 87). Under LOAC, the investigative obligation is thus a component part of normal military command and discipline.

Human rights bodies, however, take a stricter stance regarding the chain of command’s involvement in military investigations. In the Al-Skeini case, for instance, the European Court of Human Rights found that the United Kingdom had violated its legal obligations due to the commander’s key role in the investigatory process (paras. 171-72). Findings such as this, combined with due process concerns, have led European States to implement changes to their military justice systems to remove any command influence from military police investigations and subsequent prosecutions.

Human rights courts have additionally highlighted the necessity for investigations to be completed in a timely and transparent manner (see e.g., Al Skeini, para. 167). Nonetheless, they are not blind to the impacts of armed conflict on States’ abilities to investigate. This is evident from the Hanan case, in which the European Court of Human Rights took into account the fact that the deaths occurred during active hostilities when assessing whether Germany had complied with its investigative obligations (paras. 200-36). Although Germany’s investigation was far from perfect, the Court found that it was effective in view of the difficult circumstances in which the State was operating.

The challenge for the armed forces is how to know at the time of an investigation whether the steps they are taking are sufficient. As one report into the United Kingdom’s investigatory processes concluded,

with the legal landscape still so changeable, the only safe assumption must be that any [military] investigation should come as close to the Human Rights standards applied to civilian investigations as it possible given the operational context. Where there are legitimate reasons for not meeting the standard, these should be meticulously documented (p. 12).

This is sound advice for States party to the European Convention on Human Rights. However, the impact of IHRL on armed forces’ investigations into civilian harm varies considerably according to the human rights treaties to which the State is a party.

The same is true regarding the impact of the Rome Statute. If a State party to the Rome Statute does not effectively investigate alleged war crimes, there is a risk that the ICC could open its own investigation into the case, as it did regarding the United Kingdom’s operations in Iraq after 2003. Although the ICC ultimately closed its preliminary examination, it did so only after closely scrutinizing the United Kingdom’s investigative processes and criticizing the unjustified delay and the lack of independence and impartiality. Thus, although LOAC does not mandate professionalized and independent investigative processes outside the chain of command, a desire to avoid ICC investigations and prosecutions may lead States party to the Rome Statute toward this course.

Balancing Investigatory Standards Against Military Effectiveness

While the legal obligations that impact armed forces’ investigations into allegations of civilian harm vary from State to State, all military operations today are subject to unprecedented scrutiny. In the modern information environment, effective and transparent investigations into civilian harm have become a strategic imperative for all States.

Demonstrating LOAC compliance is crucial to maintaining public support for the military campaign, as well as international legitimacy and the support of allies. Moreover, conducting an effective investigation is advantageous to the armed forces concerned. Not only can this enhance a State’s military effectiveness by assisting in the identification of good practice and lessons learned, it is also an essential element of military discipline. To maintain effective command and control, soldiers must know that any incidents of concern will be promptly and appropriately investigated.

Yet the investigative standards that armed forces are required to satisfy must be balanced against the military necessity to accomplish the mission. In particular, they must take account of the very real challenges of conducting investigations in situations of armed conflict. Thus, any assessment of an investigation’s effectiveness depends heavily upon the context in which it takes place.

Several factors will influence the appropriate investigatory standards, as well as whether or not the investigation should remain within the chain of command. First, the armed forces have more latitude in the steps they take during an administrative, as opposed to a criminal, investigation. While criminal investigations are necessary when the evidence suggests the possible commission of a war crime or other criminal offense, administrative investigations can address other causes of civilian harm when there is no suggestion of any criminal conduct. Administrative investigations allow the armed forces a greater degree of flexibility in how they conduct the inquiry and can be extremely effective in establishing the truth of what happened and ensuring enhanced civilian protection.

Second, the operational context will heavily influence the investigatory steps that the armed forces can feasibly take. Numerous considerations may need to be weighed in the balance including the degree of control the State has over the situation, the security of investigative personnel, the location of witnesses, and the attitude of the local population.

A third key factor is the severity of the allegation. If the incident is serious, involving the suspected commission of a war crime or high numbers of unanticipated civilian casualties, for example, the State might be required to go to greater lengths to overcome investigatory hurdles. Moreover, in such circumstances, a commander would be well advised to refer the matter to an external and independent investigative body. This might be necessary not only to ensure compliance with the State’s obligations under IHRL and the ICC Statute, but also to enhance the legitimacy of the investigation and perceptions of fairness.

Fourth, to ensure that mission success is properly weighed in the balance, the wider circumstances are relevant, including the operational environment, the number of ongoing investigations, and the resources available to the unit concerned. Taking these factors into account, a degree of prioritization may be necessary so that the armed forces can allocate scarce resources to the most important tasks and to those investigative steps that are most likely to prove fruitful.

This may be a particularly important consideration in the conflicts of the future. While States have undertaken wide-ranging investigations during the counter-insurgency fights of recent decades, future conflict might involve higher intensity combat, greater numbers of civilian casualties, proportionally fewer military lawyers, and a requirement for units to continually disperse and relocate. In such circumstances, the feasibility of conducting many investigative steps may be limited and the military imperative to devote precious resources to the ongoing fight, rather than to investigating civilian harm, may be overwhelming.

Whatever the surrounding circumstances, the effectiveness of States’ investigations during armed conflict is likely to be enhanced through prior planning. States’ ability to plead the infeasibility of certain investigatory steps might be limited if, as part of the planning process, they have not anticipated the requirement to address allegations of civilian harm. Effective operational record keeping is also key, throughout the investigative process. This allows the armed forces to demonstrate the steps they have taken even if an allegation of civilian harm arises long after the relevant operation has concluded.

Finally, regarding transparency, LOAC imposes no obligation on States to inform the public regarding their armed forces’ investigations, or to notify victims or their families of the outcome. There may be strong operational reasons for not releasing information, such as the sensitivity of the relevant intelligence or operational tactics, or the possibility of putting witnesses at risk.

Nonetheless, a failure to keep victims and the public informed can lead to reputational harm and reduced public confidence in the armed forces and their mission. States’ armed forces should therefore seek to engage with victims and the public regarding their investigations when it is feasible to do so. Internal transparency within the State’s own armed forces is also essential to ensure that lessons can be learned from the investigations conducted and future harm to civilians can be minimized.

Concluding Thoughts

The wars of the future, like those of the past, will continue to be fought among the civilian population and to cause civilian harm. Faced with such incidents, armed forces must decide whether to investigate and if so, how those investigations should be conducted. These decisions are not straightforward. While legal obligations combined with considerations of legitimacy and accountability call for thorough investigations, the realities of combat might preclude many investigative steps.

A balance must therefore be struck. States’ armed forces must weigh the imperative to defeat the enemy and devote only those resources they can feasibly spare to investigations of potential civilian harm against the legal and other requirements that call for thorough and effective investigations. The choices made in this regard will vary from State to State. They will clearly be influenced by the State’s treaty obligations, as well as its domestic laws and military culture. The operational circumstances are also key.

Thus, it is entirely inappropriate to dictate either the investigatory steps States’ armed forces must take, or who must investigate. States must be accorded a discretion in this respect so that they can make investigatory decisions that account for the operational context and the seriousness of the allegations, as well as wider military concerns. Feasibility is key to all investigative procedures that States’ armed forces undertake. Whether imposed by policy or law, investigatory standards that ignore feasibility and operational realities would prove unacceptable to States and ultimately detrimental to the proper balance between humanity and military necessity in armed conflict.

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Jennifer Maddocks is an Assistant Professor in the Department of Law and Philosophy at the United States Military Academy, West Point and the Managing Editor for Articles of War.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published.

Photo credit: Cpl. Ryan C. Heiser