International Humanitarian Law: The Rules of Armed Conflict

The Law That Governs How Wars Are Fought

On August 22, 1864, twelve nations signed the first Geneva Convention in Switzerland, establishing for the first time that sick and wounded soldiers must be cared for regardless of which side they fight on. That single document launched what is now called international humanitarian law (IHL) — a body of rules that has expanded over 160 years into one of the most codified areas of public international law. War may be sanctioned; how it is conducted is not left to discretion.

IHL is sometimes called the law of armed conflict or the law of war. Its core purpose is pragmatic rather than utopian: not to eliminate war, but to limit its destructiveness by protecting those who are not, or no longer, participating in hostilities. It applies to all parties to a conflict, whether or not the conflict was lawfully initiated.

The Geneva Conventions: Four Treaties, One Framework

The modern IHL framework rests on four Geneva Conventions adopted on August 12, 1949, which have achieved universal ratification — all 196 states in the world are parties. The four conventions address distinct categories of protected persons.

In 1977, two Additional Protocols strengthened the framework. Protocol I addresses international armed conflicts and significantly expanded civilian protection rules. Protocol II — ratified by 169 states — addresses non-international armed conflicts, filling the gap for civil wars and internal fighting that the 1949 Conventions addressed only minimally.

The Three Core Principles

Three foundational principles structure all of IHL. They apply to every tactical decision a commander makes.

Distinction

Parties must at all times distinguish between combatants and civilians, and between military objectives and civilian objects. Only military objectives may be intentionally attacked. Civilians lose protection only if and for such time as they directly participate in hostilities — a formulation that has generated substantial legal debate about duration and scope.

Proportionality

An attack that may be expected to cause incidental civilian casualties or damage to civilian objects must not be excessive in relation to the anticipated concrete and direct military advantage. The rule is not a prohibition on civilian harm — it is a prohibition on disproportionate civilian harm. The military advantage must be concrete and direct, not speculative or indirect.

Precaution

Commanders must take all feasible precautions in planning and conducting attacks to avoid, or minimize to the maximum extent possible, incidental loss of civilian life and damage to civilian property. Warnings must be given before attacks affecting civilian populations unless circumstances do not permit. Precaution is constant, not situational.

Common Article 3: The Minimum Floor

Every one of the four 1949 Geneva Conventions contains an identical provision — Common Article 3 — that applies to armed conflicts not of an international character. Its guarantees are the floor below which no party may fall, regardless of whether a formal state of war exists.

• Persons taking no active part in hostilities must be treated humanely without adverse distinction based on race, religion, sex, or similar criteria
• Prohibitions include: murder, mutilation, torture, cruel treatment, hostage-taking, humiliating and degrading treatment, and extrajudicial execution
• The wounded and sick must be collected and cared for
• The International Committee of the Red Cross (ICRC) may offer its services to parties to the conflict

The simplicity is intentional. Common Article 3 was designed to be so fundamental that no government could plausibly reject it.

The ICRC's Monitoring Role

The International Committee of the Red Cross is not a UN body — it is a Swiss private association founded in 1863 that has been granted a unique mandate under IHL. The ICRC acts as a neutral intermediary between conflicting parties, visits prisoners of war and detained civilians, traces missing persons, and publicly documents violations when confidential approaches fail.

ICRC visits are not inspections. Access depends on the consent of detaining powers. The ICRC regularly has access refused in armed conflicts — most recently in significant parts of Gaza and Myanmar. When access is denied, the ICRC's silence is itself informative. Its legal authority to monitor is soft: it depends on the political cost of exclusion, not on enforcement power.

Grave Breaches and War Crimes

The Geneva Conventions created the first treaty-based definition of war crimes through the concept of "grave breaches." States are obligated to enact domestic legislation criminalizing grave breaches and either to prosecute perpetrators found on their territory or to extradite them. This is the aut dedere aut judicare principle — prosecute or extradite.

• Willful killing of protected persons
• Torture or inhumane treatment, including biological experiments
• Willfully causing great suffering or serious injury
• Unlawful deportation, transfer, or confinement
• Taking of hostages
• Extensive destruction or appropriation of property not justified by military necessity

Individual criminal responsibility for grave breaches is now codified in the Rome Statute of the International Criminal Court, which explicitly incorporates IHL definitions into its Article 8 war crimes list.

Customary IHL vs. Treaty Law

Not all IHL rules are found in treaties. Customary international humanitarian law — rules derived from consistent state practice accompanied by a belief that the practice is legally obligatory (opinio juris) — binds all states, including those not party to specific treaties. The ICRC's 2005 study identified 161 rules of customary IHL covering both international and non-international armed conflicts.

Customary IHL is particularly important for armed groups operating in non-international conflicts. Non-state armed groups cannot ratify treaties, but customary IHL binds them through the obligations of the states on whose territory they operate and through the principle that parties to a conflict are bound by applicable international law regardless of their formal legal status.

Application Challenges: Syria and Ukraine

The gap between IHL rules and their enforcement is stark. In Syria, the UN Commission of Inquiry documented systematic violations by multiple parties from 2011 onward: attacks on hospitals, use of barrel bombs and chemical weapons against civilian populations, siege warfare, and torture in detention. Syria is party to the Geneva Conventions and their Additional Protocols. The violations were not the result of legal ambiguity — they were the result of impunity.

In Ukraine, Russia's 2022 invasion generated the largest IHL documentation effort in decades. The International Criminal Court issued arrest warrants for President Vladimir Putin in March 2023 for the unlawful deportation of Ukrainian children — a grave breach of Convention IV. The case illustrates both the reach of IHL and its enforcement limits: Russia is not a party to the Rome Statute and has not surrendered Putin.

IHL's authority rests on reciprocity, shame, and long-term interest — not on police power. Its rules are clear. Enforcement remains the unresolved problem of the international legal order.