War crimes and crimes against humanity are both serious international crimes, but they are defined by different legal circumstances. A war crime is a serious violation of international humanitarian law connected to an armed conflict. A crime against humanity is one of a specified group of acts—such as murder, torture, enslavement, deportation or persecution—committed as part of a widespread or systematic attack directed against a civilian population. Unlike war crimes, crimes against humanity do not require an armed conflict.
The distinction matters because the same underlying conduct can sometimes qualify as both. Torture, for example, can be a war crime when committed in connection with an armed conflict and can also constitute a crime against humanity when committed as part of a widespread or systematic attack against civilians. The legal label therefore depends not only on what happened, but on the surrounding circumstances, the applicable law and what the evidence establishes.
The simplest distinction
The easiest way to understand the difference is to ask two different questions.
For a war crime: Was the conduct connected to an armed conflict and did it seriously violate the rules governing that conflict?
For a crime against humanity: Was the conduct part of a widespread or systematic attack directed against a civilian population?
Those questions can overlap, but they are not interchangeable.
| Legal issue | War crime | Crime against humanity |
|---|---|---|
| Connection to armed conflict | Required | Not required |
| Central legal framework | International humanitarian law and international criminal law | International criminal law |
| Victims | Can include civilians, detainees, wounded combatants and others protected by IHL | Requires an attack directed against a civilian population |
| Typical conduct | Deliberate attacks on civilians, torture, hostage-taking, pillage, certain unlawful attacks and sexual violence | Murder, extermination, enslavement, deportation, imprisonment, torture, persecution, enforced disappearance and certain sexual violence |
| Contextual requirement | Must be sufficiently connected to an armed conflict | Must form part of a widespread or systematic attack |
| Can occur during peacetime? | No | Yes |
| Must be part of a large-scale pattern? | Not necessarily; some war crimes can be individual or isolated serious violations | Yes, the broader attack must be widespread or systematic |
| Main question | Were the laws of armed conflict seriously violated? | Was the act part of a widespread or systematic attack on civilians? |
What is a war crime?
War crimes are serious violations of international humanitarian law for which individuals can incur criminal responsibility.
International humanitarian law, also known as the law of armed conflict or the law of war, regulates conduct during armed conflicts. It protects civilians and people who are no longer participating in hostilities and limits the means and methods that parties can use to fight.
Examples can include:
- Intentionally attacking civilians
- Intentionally attacking civilian objects in circumstances prohibited by IHL
- Torturing or cruelly treating protected persons
- Taking hostages
- Pillage
- Certain forms of unlawful deportation or transfer
- Rape and other forms of sexual violence
- Recruiting or using children under 15 in hostilities
- Certain prohibited attacks, weapons or methods of warfare
The precise list varies according to the type of armed conflict and the applicable treaties and customary international law.
A war crime requires an armed conflict
This is the defining contextual feature.
There must be an international or non-international armed conflict, and the alleged conduct must have a sufficient connection to that conflict.
An act of torture committed by police during ordinary peacetime repression could be a serious crime and potentially engage international human-rights law, but it would not become a war crime simply because the torture was severe.
If the same type of torture occurred in connection with an armed conflict and satisfied the elements of a recognized war crime, the legal classification could be different.
What is a crime against humanity?
Under Article 7 of the Rome Statute, crimes against humanity consist of specified acts committed as part of a widespread or systematic attack directed against a civilian population, with knowledge of the attack.
The listed acts include:
- Murder
- Extermination
- Enslavement
- Deportation or forcible transfer
- Imprisonment or other severe deprivation of physical liberty in violation of fundamental international-law rules
- Torture
- Rape and specified forms of sexual violence
- Persecution
- Enforced disappearance
- Apartheid
- Other inhumane acts of comparable character under the applicable law
The critical point is that the individual act is not enough.
A murder does not automatically become a crime against humanity because the victim was a civilian. Investigators must establish the required broader context.
What does “widespread or systematic” mean?
These two words describe alternative ways of satisfying the contextual requirement.
Widespread generally concerns the scale of the attack—such as the number of victims, geographical reach or extent of the conduct.
Systematic concerns an organized or methodical pattern rather than random or isolated acts.
UN investigative mechanisms describe the distinction in broadly these terms: an attack can be widespread because of its large scale or geographic extent, while a systematic attack involves organized, non-random violence.
Importantly, the word “or” matters.
An attack does not necessarily have to be both widespread and systematic under the Rome Statute. Evidence establishing either characteristic can satisfy the contextual requirement, provided the other legal elements are also established.
A crime against humanity does not require a war
This is probably the biggest difference.
Crimes against humanity can occur during an armed conflict, but they can also occur in peacetime.
A government that systematically imprisons, tortures and murders civilians as part of a widespread or systematic attack can potentially commit crimes against humanity even if no armed conflict exists.
The UN’s Independent Investigative Mechanism for Myanmar, for example, notes that crimes against humanity do not require a connection to an armed conflict, unlike war crimes.
That makes crimes against humanity particularly relevant to situations involving state repression, mass persecution or organized violence that fall short of the legal definition of an armed conflict.
The same act can be both
The categories are not mutually exclusive.
Imagine a hypothetical conflict in which government forces deliberately torture hundreds of captured civilians as part of an organized campaign.
If the conduct violates the applicable rules of armed conflict, the torture could constitute a war crime.
If it is also part of a widespread or systematic attack directed against a civilian population, the same conduct could constitute a crime against humanity.
The two offenses would be based on different contextual elements.
The ICRC specifically notes that acts such as torture, rape, enslavement and unlawful imprisonment can potentially be punishable as ordinary crimes, war crimes or crimes against humanity depending on the circumstances.
Why civilian status matters differently
The two categories also approach victims differently.
War crimes can protect a range of people under international humanitarian law, including civilians and people who are no longer participating in fighting, such as wounded combatants and detainees.
Crimes against humanity, by contrast, require the underlying attack to be directed against a civilian population.
That does not mean every individual victim must be completely uninvolved in a conflict in every conceivable circumstance. The legal analysis focuses on the civilian population that is the object of the broader attack and the circumstances of the particular conduct.
The distinction is therefore about the context of the attack, not simply whether an individual victim happened to be carrying a weapon at a particular moment.
Why an isolated act can be a war crime but not a crime against humanity
Suppose a soldier deliberately tortures a detainee during an armed conflict.
If the legal requirements for torture as a war crime are satisfied, that individual incident can potentially constitute a war crime.
But a single incident would ordinarily not establish a crime against humanity by itself because the latter requires the act to form part of a widespread or systematic attack directed against a civilian population.
This is one reason the two categories should not be treated as synonyms.
War-crimes law focuses heavily on the relationship between the conduct and the armed conflict. Crimes-against-humanity law focuses on the relationship between the individual act and a broader attack against civilians.
What about murder?
Murder illustrates the difference particularly well.
A deliberate killing during an armed conflict can be a war crime when the victim is protected under IHL and the applicable legal requirements are satisfied.
But the killing does not automatically become a crime against humanity.
For that classification, prosecutors would need evidence connecting the murder to a widespread or systematic attack directed against a civilian population.
The surrounding pattern therefore matters.
One unlawful killing and thousands of killings carried out as part of an organized campaign may involve very different international-criminal-law questions.
What about torture?
Torture can fall into all three categories of ordinary crime, war crime and crime against humanity, depending on the circumstances.
During an armed conflict, torture of a protected person can constitute a war crime.
During peacetime, torture can still violate international human-rights law and national criminal law.
If torture is part of a widespread or systematic attack against a civilian population, it can additionally constitute a crime against humanity.
The physical act may look similar in each case. The surrounding legal circumstances determine the classification.
War crimes focus on the conduct of war
International humanitarian law is sometimes described as jus in bello: the law governing how parties conduct themselves once an armed conflict exists.
It regulates matters such as:
- Who may be attacked
- Who must be protected
- How attacks must be conducted
- Treatment of detainees
- Protection of medical personnel and facilities
- Treatment of the wounded
- Certain weapons and methods of warfare
- Humanitarian access
IHL does not, by itself, determine whether a state was legally entitled to start the war. That is a separate question governed principally by the UN Charter and the law on the use of force.
Consequently, a state might have an unlawful reason for using force while particular conduct during the conflict could still have to be assessed separately under IHL.
Likewise, the fact that a war was lawfully initiated does not give either side permission to commit war crimes.
Crimes against humanity focus on attacks against civilians
Crimes against humanity address another kind of international criminality: serious acts carried out as part of a broader attack against civilians.
The concept is therefore capable of covering organized repression that occurs outside conventional warfare.
The contextual requirement is central because it separates crimes against humanity from ordinary isolated offenses.
A government official committing one unauthorized assault is not, without more, committing a crime against humanity. Evidence would need to establish the broader attack and the individual’s connection to it.
Is genocide the same thing?
No.
Genocide is a separate international crime.
Under the Rome Statute, genocide requires certain prohibited acts committed with the specific intent to destroy, in whole or in part, a national, ethnic, racial or religious group, as such.
That specific intent is what makes genocide legally distinct from both war crimes and crimes against humanity.
There can be overlap. For example, killing civilians during an armed conflict might potentially be relevant to war-crimes, crimes-against-humanity and genocide investigations.
But each offense has different legal elements.
The presence of one does not automatically establish the others.
Why the distinction matters in an investigation
When an international investigation examines alleged mass abuses, investigators cannot simply determine that an incident was “atrocious” and assign a legal label.
They have to establish the elements of a particular offense.
For a suspected war crime, investigators might ask:
- Was there an armed conflict?
- Was the conduct sufficiently connected to that conflict?
- Who was the victim?
- What rules of IHL applied?
- Was the conduct prohibited?
- What did the accused know or intend?
For a suspected crime against humanity, investigators might ask:
- Was there an attack directed against a civilian population?
- Was that attack widespread or systematic?
- Was the particular act part of that attack?
- Did the accused know about the broader attack?
- Which underlying crime was committed?
Those questions explain why international investigations can take considerable time even when individual incidents appear straightforward.
What does this mean for UN investigations?
A UN fact-finding mission or commission of inquiry can investigate allegations of either war crimes or crimes against humanity, depending on its mandate.
It may conclude that available evidence provides reasonable grounds to believe particular violations occurred or that a broader pattern meets the legal definition of a particular international crime.
But such a finding is not itself a criminal conviction.
The ICRC notes that serious violations of IHL can give rise to individual criminal responsibility and that states have mechanisms for investigating and prosecuting war crimes.
A separate court or prosecutor would have to determine whether it has jurisdiction and whether the evidence satisfies the requirements for criminal proceedings.
Why the distinction matters in the Iran context
The difference becomes especially important when reports describe both wartime attacks and domestic repression.
An alleged unlawful attack during an armed conflict raises questions under the law of armed conflict and may constitute a war crime if the necessary elements are established.
By contrast, allegations that security forces carried out killings, torture, arbitrary imprisonment or disappearances as part of a widespread or systematic attack against civilians raise the separate legal question of crimes against humanity.
The same government could therefore face allegations under both categories arising from different conduct—or, in some circumstances, from overlapping conduct.
The legal analysis should not begin with the political identity of the accused. It should begin with the evidence and the elements of the alleged offense.
The key distinction is context
The clearest way to remember the difference is:
War crime = a serious violation of the laws of armed conflict connected to an armed conflict.
Crime against humanity = a specified serious crime committed as part of a widespread or systematic attack against a civilian population.
The two categories can overlap, but neither automatically implies the other. A war crime does not have to be part of a widespread or systematic attack, while a crime against humanity does not require a war.
That distinction is more than terminology. It determines what investigators must prove, what evidence matters and which legal framework applies.
**The most important question in any alleged international crime is therefore not simply what happened, but what legal context surrounded it. The same act—murder, torture, rape or unlawful imprisonment—can carry different legal classifications depending on whether it was connected to an armed conflict, formed part of a widespread or systematic attack against civilians, or satisfied the distinct elements of another international crime.**