II - Principles

2.2 MILITARY NECESSITY
Military necessity may be defined as the principle that justifies the use of all measures needed to defeat the enemy as quickly and efficiently as possible that are not prohibited by the law of war. Military necessity has been defined in military publications, judicial decisions, and scholarly works.

2.2.1 Military Necessity as a Justification. Military necessity justifies actions, such as destroying and seizing persons and property. Thus, military necessity underlies law of war concepts that explain when persons and property may be the object of attack, e.g., the concepts of “taking a direct part in hostilities” and “military objective.”
Military necessity may justify not only violence and destruction, but also alternative means of subduing the enemy. For example, military necessity may justify the capture of enemy persons, or non-forcible measures, such as propaganda and intelligence-gathering.
Military necessity also justifies certain incidental harms that inevitably result from the actions it justifies. The extent to which military necessity justifies such harms is addressed by the principle of proportionality.