|By Françoise Hampson
Military necessity is a legal concept used in international humanitarian law (IHL) as part of the legal justification for attacks on legitimate military targets that may have adverse, even terrible, consequences for civilians and civilian objects. It means that military forces in planning military actions are permitted to take into account the practical requirements of a military situation at any given moment and the imperatives of winning. The concept of military necessity acknowledges that even under the laws of war, winning the war or battle is a legitimate consideration, though it must be put alongside other considerations of IHL.
It would be overly simplistic to say that military necessity gives armed forces a free hand to take action that would otherwise be impermissible, for it is always balanced against other humanitarian requirements of IHL. There are three constraints upon the free exercise of military necessity. First, any attack must be intended and tend toward the military defeat of the enemy; attacks not so intended cannot be justified by military necessity because they would have no military purpose. Second, even an attack aimed at the military weakening of the enemy must not cause harm to civilians or civilian objects that is excessive in relation to the concrete and direct military advantage anticipated. Third, military necessity cannot justify violation of the other rules of IHL.
Moreover, the action in question has to be in furtherance of a military, not a political, goal. This poses obvious problems of characterization. Is persuading the enemy to surrender a military or political goal? Is “persuading” the enemy to surrender by aerial bombardment a military or political goal.
What constitutes a military objective will change during the course of a conflict. As some military objectives are destroyed, the enemy will use other installations for the same purpose, thereby making them military objectives and their attack justifiable under military necessity. There is a similarly variable effect on the determination of proportionality. The greater the military advantage anticipated, the larger the amount of collateral damage—often civilian casualties—which will be “justified” or “necessary.” This flexibility also appears with regard to the prohibition of the use of weapons that cause “superfluous injury or unnecessary suffering.” The greater the necessity, the more suffering appears to be justified. Thus, even in the Advisory Opinion on the Legality of the Use of Nuclear Weapons the majority of judges in the International Court of Justice in The Hague left open the possibility that a State might be able to justify its use of nuclear weapons where the very survival of the State was under serious threat.
State practice recognizes that judgments about military necessity often require subjective evaluations with incomplete information on the battlefield and imperfect knowledge of where the failure to take action might lead. For this reason, great discretion has always been attached to commanders’ judgments, especially those made under battlefield conditions. Rarely, if ever, is the judgement of a field commander in battle—balancing military necessity and advantage—subject to legal challenge, let alone criminal sanction. An exception would be when the method of warfare used by the commander was illegal per se, and therefore not covered by the claim of military necessity.
In some cases, there is a presumption that certain actions are unlawful; it was not possible to prohibit them in absolute terms but they are unlawful unless justified by “imperative military necessity.” This qualification of “absolutely necessary” or “for reasons of imperative military necessity” puts a significant burden of proof on those invoking the exception. Examples include the Fourth Geneva Convention, which restricts the internment of protected persons and the transfer or deportation from an area of occupied territory; Additional Protocol I, which would normally prohibit a scorched-earth policy but which allows it in exceptional circumstances in national territory; and Additional Protocol II, which normally prohibits the internal displacement of the civilian population.
In the course of hostilities, these rules impose significant restraints on the conduct of law-abiding forces, but those forces may be able lawfully to invoke military necessity where their very survival or the requirements of winning the conflict are at stake.