Military Necessity

Military necessity is one of the foundational principles of international humanitarian law (IHL), alongside distinction, proportionality, and humanity. It allows a party to an armed conflict to use the level and kind of force required to achieve a legitimate military objective — the partial or complete submission of the enemy — provided that force is not otherwise forbidden by treaty or customary law.

The concept was first codified in modern form in the Lieber Code of 1863, drafted by Francis Lieber for the Union Army during the U.S. Civil War. Article 14 defined it as "those measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war." It later shaped the Hague Regulations of 1899 and 1907 and the Geneva Conventions of 1949 and their 1977 Additional Protocols.

Crucially, military necessity is not a stand-alone justification that overrides IHL. It operates within the rules: a commander cannot invoke necessity to attack civilians, torture prisoners, or use prohibited weapons. As the International Military Tribunal at Nuremberg stressed in cases such as United States v. List (the Hostages Trial, 1948), necessity cannot excuse violations of the laws of war except where a specific rule itself contains a necessity exception (for example, the destruction of property under Article 23(g) of the Hague Regulations, or Article 53 of Geneva Convention IV).

The principle has two operational functions:

• Permissive: authorising the use of force against lawful military objectives, defined in Article 52(2) of Additional Protocol I as objects that by their nature, location, purpose, or use make an effective contribution to military action.
• Restrictive: prohibiting destruction or suffering not required to secure a military advantage — sometimes called the prohibition on wanton destruction, reflected in Article 8(2)(b)(xiii) of the Rome Statute of the International Criminal Court.

In practice, military necessity is assessed alongside proportionality and distinction, and remains contested in debates over urban warfare, dual-use infrastructure, and cyber operations.