International Humanitarian Law (IHL) — The Laws of War

International Humanitarian Law encompasses two historical streams that have merged into a unified body of law. The Hague stream — originating from the 1899 and 1907 Hague Conventions — governs the means and methods of warfare: what weapons can be used, what targets can be attacked, how occupied territories must be governed. The Geneva stream — four conventions adopted in 1949, supplemented by the 1977 Additional Protocols — governs the protection of persons who are no longer fighting: wounded soldiers, prisoners of war, shipwrecked sailors, and civilians. Both streams are now considered part of customary international law binding on all states, regardless of treaty ratification. The International Committee of the Red Cross (ICRC) serves as the guardian of IHL, conducting confidential visits to prisoners of war and detainees and monitoring compliance.

The principle of distinction is IHL's foundational requirement: all parties must at all times distinguish between civilians and combatants, and between civilian objects and military objectives. Attacks may only be directed at military objectives — defined as objects that by nature, location, purpose, or use make an effective contribution to military action, whose partial or total destruction offers a definite military advantage. Civilian objects — hospitals, schools, places of worship, cultural property, residential neighborhoods — may not be targeted. The civilian status of a person or object is presumed in cases of doubt. This principle is violated when military forces deliberately target civilian infrastructure, use civilian shields, or employ weapons incapable of discriminating between military and civilian targets.

Proportionality and precaution operate as limits on attacks against legitimate military objectives. Even if a target is a genuine military objective, an attack is prohibited if it may be expected to cause incidental civilian casualties or damage excessive in relation to the concrete and direct military advantage anticipated. The proportionality analysis requires commanders to assess expected civilian harm against expected military gain — not in hindsight, but based on information reasonably available at the time. The precaution obligation requires parties to take all feasible measures to avoid or minimize incidental civilian casualties, including giving effective advance warning of attacks affecting the civilian population when feasible. These principles are not merely aspirational — violations of distinction, proportionality, or precaution constitute war crimes under Additional Protocol I and the Rome Statute.