A deeply troubling provision in the Defense Department’s new Law of War Manual suggests that commanders are not legally required to minimize civilian casualties when selecting between different targets. According to the manual, even if commanders expect to gain the same or similar military advantage from striking target A as from striking target B, commanders are under no legal obligation to select the target that places the fewest civilians in harm’s way.

As military and humanitarian lawyers know, Protocol I to the Geneva Conventions provides that “[w]hen a choice is possible between several military objectives [that is, targets] for obtaining a similar military advantage, the objective to be selected shall be that the attack on which may be expected to cause the least danger to civilian lives.” Let us call this rule “the target selection rule.” However, according to the manual, “this rule is not a requirement of customary international law.” Since the United States is not a party to Protocol I, it follows that, according to the DOD, the United States is not legally required to select targets so as to reduce collateral harm to civilians.

In my view, the manual’s position on target selection, like its stance on killing involuntary human shields, is both legally and morally unsustainable. This position misrepresents customary international law, fits uneasily with other provisions of the manual itself, and almost certainly does not describe actual US targeting practices. The DOD should abandon this untenable position.

According to the ICRC, “[s]tate practice establishes [the target selection] rule as a norm of customary international law.” The target selection rule is recognized by the law of war manuals of Australia, Canada, France, Italy, Spain, Sweden, and the United Kingdom, among others, as well as by the Group of Experts responsible for the Humanitarian Policy and Conflict Research Manual. Indeed, the ICRC could find “only one instance of apparently contrary practice,” namely a 1991 statement by the US Army.

Strikingly, the manual’s only support for its position is a citation to that 1991 Army statement. According to that statement, the target selection rule “is not mandatory. An attacker may comply with it,” but is not legally required to do so. On this view, an attacker faced with such a choice — between killing more civilians and killing fewer civilians to achieve the same military advantage — may simply flip a coin, so far as the law is concerned. Not surprisingly, no other country in the world agrees with the Army’s 1991 statement or shares the DOD’s current position.

To illustrate the DOD’s position, consider the following scenario:

Two Roads: Defenders use Road A to transport weapons and equipment from a well-fortified military base to a highway intersection and then use Road B to transport the same weapons and equipment from the intersection to the front line. Attackers can prevent the weapons and equipment from reaching the front line by destroying either road. However, Road A runs through a densely populated city, while Road B runs through empty countryside. If attackers destroy Road A then they expect to kill at least 10 civilians. In contrast, if attackers destroy Road B then they expect to kill no civilians.

Let us stipulate, for the sake of argument, that it would not be unlawfully disproportionate to collaterally kill 10 civilians in order to prevent the weapons and equipment from reaching the front line. Of course, in the scenario, it is unnecessary to kill any civilians to achieve this military advantage. Yet, according to the manual, the attackers may lawfully destroy Road A rather than Road B, collaterally killing 10 civilians in order to achieve a military advantage that they can achieve without killing any civilians. This result is morally intolerable, as is the position that generates it.

Indeed, the DOD’s position on target selection is difficult to reconcile with its own statements regarding precautions and proportionality. For example, the manual states that “[c]ombatants must take feasible precautions in conducting attacks to reduce the risk of harm to civilians” yet suggests that combatants need not select targets for attack so as to reduce the risk of harm to civilians (emphasis added). Similarly, the manual states that, when “the use of certain weapons rather than others may lower the risk of incidental harm, while offering the same or superior military advantage,” combatants are legally required to select the less risky weapons. In other words, according to the manual, combatants must select weapons that lower the risk of incidental harm but need not select targets that lower the risk of incidental harm. The conjunction of these views seems rationally inexplicable.

In addition, the manual accepts “the proportionality rule,” namely that “[c]ombatants must refrain from attacks in which the expected loss of life or injury to civilians … would be excessive in relation to the concrete and direct military advantage expected to be gained.” It is indeed wrong to disproportionately kill civilians to achieve a military advantage too small to justify killing them. However, if anything, it is even worse to kill more civilians to achieve a military advantage that one can achieve while killing fewer civilians or no civilians. To prohibit the former but not the latter gets things backwards.

Finally, the manual accepts that the principle of humanity “forbids the infliction of suffering, injury, or destruction unnecessary to accomplish a legitimate military purpose.” The DOD’s position on target selection appears to ignore this fundamental principle of customary international law.

I encourage readers who reject the manual’s position on target selection, or its position on killing involuntary human shields, to respond to the DOD’s invitation and contact them at osd.pentagon.ogc.mbx.ia-law-of-war-manual-comments@mail.mil.