Editor’s Note: Just Security is holding a “mini forum” on the new Defense Department Law of War Manual. This post is the first in a series. Stay tuned for more from Eric Jensen and others.

On June 12, the US Defense Department’s Office of the General Counsel released its long-awaited Law of War Manual. Although the manual will prove a treasure trove for academic commentary, its primary purpose is to inform and assist practicing US lawyers charged with advising armed forces during armed conflict. The question of whether its format, size, organization, and content will prove appropriate or adequate to the task will doubtless provoke strong opinions.

Prof. Eric Jensen and I have invited, and Just Security has generously agreed to host, a selection of international lawyers to comment on the manual in these respects. Each commentator is deeply familiar with US perspectives on the law of war. Many have instructed or advised US forces directly. And many were involved in the formulation and drafting of US government instructional materials and legal doctrine during the nearly 60 years that passed since publication of the manual’s predecessor.

To kick things off, I will comment briefly on the new manual’s treatment of the principles of the law of war. I will note especially differences from preceding expressions and understandings of these principles. Overall, the manual offers a significant recalibration of many military lawyers’ understandings of both the content and operation of law of war principles. The manual is in many ways a rejection of the rule-like refinements military lawyers had developed to operationalize these principles and signals a return to very broad, generally applicable legal principles in a truer sense.

In 1956, the US Army Field Manual on the Law of Land Warfare noted the basic principles of military necessity, humanity, and chivalry. Since then other manuals and commentaries have offered various expressions of the principles of the law of war. Reputable law of war sources identify as few as two and as many as six principles. Recent DOD instructional materials and manuals appeared to settle on four principles including: military necessity, discrimination, proportionality, and unnecessary suffering. Informed and improved by extensive practice in armed conflict, successive US military sources refined these principles such that on the eve of the new manual’s publication each enjoyed a relatively high degree of clarity, precision, and acceptance. Each principle featured routinely and figured prominently in the legal advice given to US military commanders. 

The new manual’s most deliberate and comprehensive expression of the principles of the law of war is found at paragraph 2.1, which states, “Three interdependent principles – military necessity, humanity, and honor – provide the foundation for other law of war principles, such as proportionality and distinction, and most of the treaty and customary rules of the law of war.”

Neither the manual’s expression of military necessity nor that of distinction will present much surprise to the eyes of military lawyers. However, the principles of humanity, proportionality, and honor will likely require significant recalibration of US military lawyers’ thinking and practice.

The manual’s reference to humanity is perhaps its most drastic adjustment to existing doctrine. Overall, the manual’s notion of humanity abandons recent refinements of that concept in favor of a more general approach.

Military legal doctrine issued in the long period following publication of the manual’s 1956 predecessor eventually identified “unnecessary suffering” as the principle prohibiting resort to means or methods unrelated to or beyond those required to accomplish a military objective. One might even say that these refinements had reduced unnecessary suffering from a principle into something more closely resembling a rule or criminal law charge. Under the US view, unnecessary suffering even included a specific element of scienter, requiring that suffering be calculated or deliberate in order to constitute a violation.

The manual does not abandon the concept of unnecessary suffering entirely — it remains an important, though not exclusive aspect of humanity. In fact, the manual’s first reference to principles appears at paragraph 1.3.4, which observes that “[t]he main purposes of the law of war are: protecting combatants, noncombatants, and civilians from unnecessary suffering.”

To most readers, this will appear an entirely uncontroversial observation. However, some lawyers, especially those indoctrinated to the law of war through modern US instructional materials and legal doctrine produced by the various services, may find inclusion of civilians in the concept of unnecessary suffering somewhat surprising.

As a cardinal principle of the law of war, unnecessary suffering has traditionally concerned protections exclusively for combatants and other persons who may be lawfully targeted. Civilians and noncombatant have not been regarded within the ambit of the principle of unnecessary suffering as they more usually derive protection from the principle of discrimination which prohibits, subject to their not taking direct part in hostilities, combatants from targeting them entirely.

Still, the manual’s view is not unprecedented. In fact, its predecessor, the 1956 Army Field Manual extended its view of unnecessary suffering to noncombatants, though not to civilians (para. 2). It is possible the new manual incorporates noncombatants and civilians to account for instances of their direct participation in hostilities. Recall that civilians and noncombatants may be targeted with lethal force if they take direct part in hostilities. However, a far simpler way to achieve that purpose would have been simply to incorporate the phrase.

The manual’s resurrection of the term “humanity” broadens the reach of the principle in other respects as well. According to paragraph 2.3.2, it is the principle of humanity that animates treatment standards during capture, the protection of civilian objects and medical personnel, and prohibits the use of certain inherently indiscriminate weapons. In this regard, humanity appears now to connect quite closely with the principle of discrimination, whereas it had recently evolved to be quite usefully distinct.

The manual’s expansion of previously expressed principles extends to proportionality as well. Recent US instructional materials and legal doctrine had certainly included proportionality as a principle of the law of war. Yet, these sources most often limited proportionality to targeting operations. Rarely, if ever, did these sources recite the principle of proportionality in discussion of other operations.

As with respect to unnecessary suffering, US doctrinal expressions of the principle of proportionality had evolved into rule-like statements. Most sources articulated the principle of proportionality as prohibiting attacks producing injury to civilians and damage to civilian objects “excessive in relation to concrete and direct military advantage.” By contrast, the manual articulates proportionality far more broadly, associating it with evaluations of attacks, but also with defensive positioning, unnecessary suffering and weapons use, as well as with jus ad bellum decisions to resort to force at all. The manual thus describes a far more general requirement that all actions in armed conflict be neither unreasonable nor excessive.

Perhaps most surprising to military lawyers, however, will be the manual’s revival of the principle of honor. Since 1956, the principle of honor or chivalry had largely fallen out of US law of war expressions, leaving the increasingly narrow prohibition of perfidy as one of the only clearly expressed limitations on treacherous or bad faith means and methods of warfare. Even resort to the broad term “treachery” had grown increasingly rare. The cultural, religious, ethnic, and professional asymmetries of modern combatants likely made shared senses of what constitutes honorable conduct seem dubious. To many, it may have seemed that honor was a concept better left to bygone ages of armed conflict between belligerent forces steeped in shared professional military traditions.

Consistent with its approach to the preceding principles, the manual sketches honor in exceedingly broad terms and applies it to an extensive range of battlefield conduct. Examples span prohibited methods of attack, standards of treatment during captivity, as well as organization and supervision of armed forces. The general approach of the section is to trace existing, articulated rules drawn from treaties and widely accepted custom and to explain them as examples of honor between belligerents.

While the rules and their former relationship to honor noted by the manual are no doubt accurate, one wonders what remains of the practical utility of the principle outside these examples. Most of the rules in question are well established and sufficiently refined to permit operation on their own terms without significant resort to the principle. Unless the examples are an exhaustive list of rules of honor, the reader is left to wonder what role remains for the principle in practical terms.

Reaffirmation of the principle of honor marks an important, if abstract revival of good faith as a legal restraint on military operations. But whether the principle, as envisioned by the manual, will prove sufficiently concrete, and for that matter relevant to operate as a meaningful and practical restraint in combat remains to be seen. It is highly doubtful that many military lawyers will risk their professional reputations to offer commanders and present to higher commands’ legal staffs advice or opinions based on abstract conceptions of honor.

In sum, the new manual’s section on law of war principles seems a significant re-calibration. Following decades of refinements of the very general expressions found in the 1956 Manual, inspired no doubt by the complimentary needs of operational precision and instructional clarity during an inexcusably long absence of guidance, the new manual has returned the principles of the law of war to their original, very general and abstract forms. It is unclear to what extent the manual expects military lawyers to employ these principles other than as the intellectual groundings of existing rules. They appear now very much as overarching philosophies, even sensibilities that guide all operations and even inform application of a broad range of specific rules, rather than as rules unto themselves.