What Is a War Crime? Acts, Responsibility, and Prosecution

A war crime is a serious violation of the rules that govern armed conflict, serious enough that the person who commits it can be prosecuted as an individual under international law. The main modern reference is Article 8 of the Rome Statute, the 1998 treaty that created the International Criminal Court, which lists more than 50 specific acts that qualify.¹ What separates a war crime from an ordinary atrocity is its connection to a war: the same act committed in peacetime might be murder or assault, but when it happens during armed conflict and breaks the rules that govern how wars are fought, it becomes something the entire international community can prosecute.

What Makes an Act a War Crime

Two things have to line up. First, there must be an armed conflict, either between countries or inside one. Second, the act must have a direct connection to that conflict. A robbery that happens to occur during a war is still just a robbery. But if soldiers execute prisoners, deliberately bomb a hospital, or use starvation as a weapon against a civilian population, the link to the conflict transforms those acts into crimes under international law. This “nexus” requirement is what separates war crimes from ordinary domestic offenses.

The ICC pays particular attention to acts committed as part of a plan or policy, or on a large scale, though a single incident can qualify if it is grave enough.¹

When Internal Violence Counts as Armed Conflict

Not every outbreak of domestic violence triggers war crimes law. For an internal situation to qualify as a non-international armed conflict, two conditions must be met: the armed group fighting the government or another group must be organized enough to sustain military operations, and the violence must reach an intensity that goes well beyond riots, isolated incidents, or short-lived unrest.² There is no fixed casualty threshold. Courts assess it case by case, weighing the duration of fighting, the weapons used, the displacement of civilians, and whether the armed group has a real command structure. The classification matters enormously, because once a situation crosses the line into armed conflict, the entire body of war crimes law switches on.

Crimes Against Prisoners and Other Protected Persons

The Geneva Conventions create a category of “protected persons” who are entitled to humane treatment under all circumstances: wounded and sick soldiers, prisoners of war, medical and religious personnel, and civilians in occupied territory.³ Violating these protections can constitute a “grave breach,” the most serious category of war crime.

The Fourth Geneva Convention spells out what grave breaches look like in practice: willful killing, torture, biological experiments, deliberately causing great suffering or serious bodily injury, unlawful deportation, denying a fair trial, taking hostages, and wanton destruction of property without military justification.⁴ Humiliating or degrading treatment also qualifies, even when it causes no physical injury.

The practical obligations are concrete. A force holding prisoners must provide adequate food, shelter, clothing, and medical care. Failing to do so, or deliberately withholding these necessities, is a crime in itself. Conditions of detention, not just acts of violence, can form the basis of charges. Once someone is in your custody and out of the fight, the rules shift sharply, and ignorance of those rules is not a defense.

Crimes Against Civilians and Civilian Infrastructure

The principle of distinction sits at the heart of the laws of war: combatants must differentiate between military targets and everyone else. Deliberately attacking civilians who are not participating in the fighting is one of the clearest war crimes that exists.¹ U.S. law reinforces this by making it a crime triable by military commission to intentionally attack a civilian population, with the death penalty available if any victims are killed.⁵

The protection extends beyond people to objects. Homes, schools, places of worship, and other structures without military significance cannot be targeted. Hospitals and medical facilities receive even stronger protection, and any deliberate attack against them is punishable. Indiscriminate attacks also violate the law. Using weapons that cannot be aimed at a specific military target, or launching attacks you know will cause civilian casualties wildly out of proportion to the military advantage, crosses the line even if you were not specifically trying to hit civilians.

Starvation as a Weapon

Starving civilians by cutting off food, destroying water infrastructure, or blocking humanitarian aid is a recognized war crime. The prohibition covers the deliberate destruction of crops, water treatment facilities, and irrigation systems when the goal is to harm the population rather than achieve a legitimate military objective.

Human Shields

Using civilians or other protected persons to shield military objectives is specifically listed as a war crime. That means deliberately moving civilians to military sites, or positioning military assets in civilian areas to deter attacks.⁶ Forcing detainees to enter mined buildings, scout dangerous areas, or move suspicious objects also falls under this prohibition. The crime attaches to the party using the shields; it does not relieve the attacking side of its own obligation to avoid excessive civilian harm.

Cultural Property

Historic monuments, archaeological sites, museums, libraries, and archives receive specific protection under the 1954 Hague Convention. Signatory nations must both safeguard cultural property within their own territory and refrain from directing hostilities against such property in enemy territory. The ICC’s 2016 conviction for the destruction of historic mausoleums in Timbuktu, Mali, is the clearest modern example of this rule enforced in court.

Sexual Violence and Crimes Against Children

The Rome Statute explicitly lists rape, sexual slavery, forced prostitution, forced pregnancy, enforced sterilization, and other forms of sexual violence as war crimes when connected to an armed conflict.¹ Treating these as standalone offenses was a major shift. Earlier tribunals had prosecuted sexual violence, but often only as a component of torture or persecution. The Rome Statute treats it as a distinct category, reflecting that sexual violence in conflict is frequently systematic rather than incidental.

Recruiting or using children under 15 in armed conflict is also a war crime, whether through forced conscription or voluntary enlistment, and the prohibition applies in both international and internal conflicts.⁷ The ICC’s first-ever conviction, against Congolese militia leader Thomas Lubanga in 2012, was built entirely on charges of enlisting and using child soldiers.

Prohibited Weapons and Tactics

Certain weapons and battlefield tactics are banned regardless of the military advantage they might provide. The Rome Statute prohibits the use of poison or poisoned weapons.¹ The prohibition exists independently of the separate ban on chemical weapons and has been described in military manuals worldwide as grounded in the weapons’ indiscriminate and inhumane nature.⁸ Expanding bullets, designed to flatten or fragment inside the body and cause maximum tissue damage, are also classified as a war crime when used in armed conflict.

Declaring that no survivors will be taken is a war crime in its own right. So is killing or wounding an enemy through treachery, which includes faking surrender or misusing protected emblems like the Red Cross symbol to lure opponents into lowering their guard.¹ These rules protect combatants on every side. If fighters cannot trust a white flag or a Red Cross vehicle, those protections collapse for everyone, including the side that abused them.

Landmines and Cluster Munitions

Two major treaties ban entire categories of weapons. The Ottawa Convention, which entered into force in 1999, prohibits the use, stockpiling, production, and transfer of anti-personnel landmines.⁹ The Convention on Cluster Munitions imposes similar restrictions on cluster bombs, which scatter smaller submunitions over wide areas and leave behind unexploded ordnance that kills civilians for decades after a conflict ends.¹⁰ Several major military powers, including the United States, Russia, and China, have not joined either treaty.

Environmental Destruction

Launching an attack in the knowledge that it will cause widespread, long-term, and severe environmental damage clearly excessive to the anticipated military advantage is a war crime under the Rome Statute.¹¹ A separate treaty, the ENMOD Convention, goes further by prohibiting the deliberate manipulation of natural processes, such as weather modification or disruption of ecological systems, as a weapon of war.¹² These cases remain difficult to prosecute because the damage often unfolds over years, making the required intent at the moment of attack hard to establish.

Who Can Be Held Responsible

Individuals bear criminal responsibility for war crimes, not just the governments or armies they serve. A soldier who commits one is personally liable. A commander who orders one is personally liable. And a commander who knows or should know that troops under their control are committing crimes and fails to stop or punish them is also personally liable, even without giving a direct order.¹

This command responsibility doctrine is where many high-profile prosecutions are built. Proving that a general personally pulled a trigger is rarely necessary. Prosecutors instead show that the commander had effective control over the forces, knew or had reason to know about the crimes, and failed to take reasonable measures to prevent them or submit the matter for investigation.

The “Following Orders” Defense

The Rome Statute takes a middle position on whether obeying orders can excuse a war crime. A defendant can raise this defense only if they were legally obligated to follow the order, did not know it was unlawful, and the order was not “manifestly unlawful.”¹³ All three conditions must be met. Orders to commit genocide or crimes against humanity are automatically considered manifestly unlawful, so the defense can never apply to those crimes. For war crimes, the defense is theoretically available but rarely succeeds, because most of the prohibited conduct is so obviously wrong that claiming ignorance is a tough sell in any courtroom.

How War Crimes Are Prosecuted

The ICC is the primary international institution for prosecuting war crimes, but it is designed as a backstop. Under the complementarity principle built into the Rome Statute, the ICC can only take a case when the country that would normally have jurisdiction is unwilling or unable to genuinely investigate and prosecute it.¹ If a national court conducts a real prosecution, the ICC stays out. It steps in when governments shield suspects, when proceedings are a sham designed to produce an acquittal, or when a justice system has effectively collapsed.

The ICC’s reach is limited by its membership. 125 countries are states parties to the Rome Statute.¹⁴ The United States signed the Rome Statute in 2000 but declared in 2002 that it did not intend to become a party. Russia signed in 2000 and withdrew its signature in 2016. China and India never signed.¹⁵ The UN Security Council can refer situations to the ICC regardless of whether the country involved is a member.

Universal Jurisdiction

War crimes are among a small number of offenses so serious that any country can prosecute them, regardless of where they occurred or the nationality of the perpetrator or victim. This principle is rooted in the Geneva Conventions’ requirement that every signatory pass domestic laws enabling prosecution of grave breaches and either try suspects found on their territory or extradite them.¹⁶ Under customary international law, this right extends to all war crimes, including those committed in internal conflicts.

The United States has its own federal war crimes statute, which criminalizes grave breaches of the Geneva Conventions and violations of the Hague Conventions when committed by or against U.S. nationals or members of the armed forces.¹⁷ The Justice for Victims of War Crimes Act expanded this law to cover situations where the suspect is simply found within the United States, closing a gap that had previously allowed some alleged war criminals to live in the country without facing prosecution.¹⁸

Sentences and Reparations

When the ICC convicts someone of a war crime, it can impose a prison sentence of up to 30 years. Life imprisonment is available when the extreme gravity of the crime and the circumstances of the defendant justify it.¹ The ICC does not impose the death penalty. National courts prosecuting war crimes under their own laws may have different sentencing ranges, and some jurisdictions permit capital punishment for the most serious offenses.

Prosecution is not the only goal. The Rome Statute established a Trust Fund for Victims in 2004, which both implements reparations ordered by the court after a conviction and provides physical, psychological, and material support to victims and their families, including rehabilitation programs, livelihood support, and community reconciliation efforts in conflict-affected areas.¹⁹

1
International Criminal Court. Rome Statute of the International Criminal Court
2
United Nations Office for Disaster Risk Reduction. Non-International Armed Conflict
3
Office of the United Nations High Commissioner for Human Rights. Geneva Convention Relative to the Treatment of Prisoners of War
4
International Committee of the Red Cross. Fourth Geneva Convention – Article 147
5
Office of the Law Revision Counsel. 10 USC 950t – Crimes Triable by Military Commission
6
International Criminal Court. Elements of Crimes
7
International Criminal Court. Policy on Children
8
International Committee of the Red Cross. Customary IHL – Rule 72 Poison
9
United Nations Office for Disarmament Affairs. Anti-Personnel Landmines Convention
10
United Nations. Convention on Cluster Munitions
11
International Criminal Court. Policy on Addressing Environmental Damage Through the Rome Statute
12
United Nations Office for Disarmament Affairs. Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques
13
International Committee of the Red Cross. Rome Statute of the International Criminal Court – Article 33
14
International Criminal Court. The States Parties to the Rome Statute
15
United Nations Treaty Collection. Rome Statute of the International Criminal Court
16
International Committee of the Red Cross. Universal Jurisdiction Over War Crimes
17
Office of the Law Revision Counsel. 18 USC 2441 – War Crimes
18
Congress.gov. Justice for Victims of War Crimes Act
19
International Criminal Court. Trust Fund for Victims