Legal Sidebari
War Crimes: A Primer
March 15, 2022
The Russian invasion of Ukraine has given rise to numerous accusations of war crimes. This Insight
addresses the sources and content of the law of war, also known as the law of armed conflict or
international humanitarian law (IHL) as it pertains to war crimes that occur in an international armed
conflict. IHL applies to the conduct of war; it does not address the legality of the war itself. For
information about potential accountability for war crimes in international tribunals, see CRS Legal
Sidebar LSB10704, The Role of International Tribunals in the Response to the Invasion of Ukraine, by
Nina M. Hart and Stephen P. Mulligan.
Sources of International Humanitarian Law
IHL is a combination of international treaties and customary international law. The Hague Convention of
1907 generally prescribes rules of conduct for armed forces, while the Geneva Conventions and Protocol
Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of
International Armed Conflicts 1 (Protocol 1) address the rights of protected persons, such as civilians and
prisoners of war, in an international armed conflict. Not all states are parties to these and other treaties
pertaining to the law of war, but many provisions are regarded as reflecting customary international law,
which is binding on all states.
Principles of International Humanitarian Law
Certain principles undergird IHL and form the basis for the content of war crimes and serve to reduce
unnecessary suffering during war. The most important principles are military necessity, humanity, and
honor. The principles of distinction and proportionality flow from the first three. The Department of
Defense’s Law of War Manual describes their interaction as follows:
Military necessity justifies certain actions necessary to defeat the enemy as quickly and efficiently
as possible. Conversely, humanity forbids actions unnecessary to achieve that object.
Proportionality requires that even when actions may be justified by military necessity, such actions
not be unreasonable or excessive. Distinction underpins the parties’ responsibility to comport their
behavior with military necessity, humanity, and proportionality by requiring parties to a conflict to
apply certain legal categories, principally the distinction between the armed forces and the civilian
population. Lastly, honor supports the entire system and gives parties confidence in it. (Citations
omitted).
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The main purposes of the law of armed conflict are:
Protecting combatants, noncombatants, and civilians from unnecessary suffering;
Providing certain fundamental protections for persons who fall into the hands of the
enemy, particularly prisoners of war, military wounded and sick, and civilians;
Facilitating the restoration of peace;
Assisting the commander in ensuring the disciplined, ethical, and effective use of military
force;
Preserving the professionalism and humanity of combatants; and
Preventing the degeneration of warfare into savagery or brutality.
United States Law: The War Crimes Act of 1996
The War Crimes Act (18 U.S.C. §2441) sets forth conduct the United States punishes as war crimes, albeit
only when U.S. nationals are involved as either perpetrator or victim. The act implements the United
States’ obligation under treaties and international law to hold perpetrators of war crimes accountable,
although some observers argue that the act is insufficient because Congress decided not to provide for
universal jurisdiction. The United States has never prosecuted anyone for violating the act.
A war crime under the act includes conduct “defined as a grave breach” in the Geneva Conventions of
1949 or prohibited by certain provisions of the Annex to the Hague Convention IV, Respecting the Laws
and Customs of War on Land of 1907. The act further proscribes the willful killing of or causing serious
injuries to civilians contrary to the provisions of the Protocol on Prohibitions or Restrictions on the Use of
Mines, Booby-Traps and Other Devices. It also proscribes certain violations defined as “a grave breach of
common Article 3” of the Geneva Conventions.
The Geneva Conventions
Grave breaches as defined in the Geneva Conventions include the following acts if committed against
protected persons or property (as applicable):
Willful killing;
Torture or inhuman treatment, including biological experiments;
Willfully causing great suffering or serious injury to body or health;
Extensive destruction and appropriation of property not justified by military necessity
and carried out unlawfully and wantonly;
Compelling a prisoner of war or other protected person to serve in the forces of a hostile
power;
Willfully depriving a prisoner of war or other protected person of the rights of fair and
regular trial;
Unlawful deportation or transfer or unlawful confinement; and
Taking of hostages.
The Hague Convention
Violations of the Annex to the Hague Convention punishable under the War Crimes Act include
provisions forbidding combatants:
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To employ poison or poisoned weapons.
To kill or wound treacherously individuals belonging to the hostile nation or army.
To kill or wound an enemy who, having laid down his arms, or having no longer means
of defense, has surrendered at discretion.
To declare that no quarter will be given (“take no prisoners”).
To employ arms, projectiles, or material calculated to cause unnecessary suffering.
To make improper use of a flag of truce, of the national flag or of the military insignia
and uniform of the enemy, as well as the distinctive badges of the Geneva Convention.
To destroy or seize the enemy’s property, unless such destruction or seizure be
imperatively demanded by the necessities of war.
To declare abolished, suspended, or inadmissible in a court of law the rights and actions
of the nationals of the hostile party. A belligerent is likewise forbidden to compel the
nationals of the hostile party to take part in the operations of war directed against their
own country, even if they were in the belligerent’s service before the commencement of
the war.
The attack or bombardment, by whatever means, of towns, villages, dwellings, or
buildings that are undefended.
The attack of buildings dedicated to religion, art, science, or charitable purposes;
historical monuments, hospitals, and places where the sick and wounded are collected,
provided they are not being used at the time for military purposes.
The pillage of a town or place, even when taken by assault.
Common Article 3
Article 3 Common to the four Geneva Conventions of 1949 provides protections during armed conflicts
not of an international nature and also protects persons during international armed conflicts who are not
entitled to protected status under any of the four conventions. Title 18, Section 2441(d), of the U.S. Code
defines grave breaches of Common Article 3 to include committing, or attempting or conspiring to
commit:
Torture (defined in a manner similar to that used by the federal torture statute [18 U.S.C.
§§2340-2340A]),
Cruel or inhuman treatment,
The performing of biological experiments,
Murder of a person taking no active part in the hostilities,
Mutilation or maiming persons taking no active part in the hostilities,
Intentionally causing serious bodily injury,
Rape,
Sexual assault or abuse, and
The taking of hostages.
The proscriptions against murder, mutilation or maiming, and causing bodily injury do not apply in cases
of collateral damage or results incident to lawful acts of warfare.
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International Law
Although the War Crimes Act sets forth conduct the United States considers serious war crimes, the
United States is not party to all treaties regarding the law of armed conflict, including notably the
Additional Protocol I to the Geneva Conventions (regulating international armed conflicts). The Rome
Statute of the International Criminal Court (ICC) probably provides the best compendium of serious war
crimes as accepted by the international community. The United States is not party to the Rome Statute but
took part in its negotiation, including regarding the inclusion of the covered war crimes. Neither Ukraine
nor Russia is party to the agreement, but Ukraine has agreed to accept the jurisdiction of the ICC for
activities that occur on its territory since 2014—an issue discussed in this CRS Legal Sidebar.
In addition to grave breaches of the Geneva Conventions set forth above, the Rome Statute provides for
punishment of:
(i) Intentionally directing attacks against the civilian population as such or against individual
civilians not taking direct part in hostilities;
(ii) Intentionally directing attacks against civilian objects, that is, objects which are not military
objectives;
(iii) Intentionally directing attacks against personnel, installations, material, units or vehicles
involved in a humanitarian assistance or peacekeeping mission in accordance with the Charter of
the United Nations, as long as they are entitled to the protection given to civilians or civilian objects
under the international law of armed conflict;
(iv) Intentionally launching an attack in the knowledge that such attack will cause incidental loss of
life or injury to civilians or damage to civilian objects or widespread, long-term and severe damage
to the natural environment which would be clearly excessive in relation to the concrete and direct
overall military advantage anticipated;
(v) Attacking or bombarding, by whatever means, towns, villages, dwellings or buildings which are
undefended and which are not military objectives;
(vi) Killing or wounding a combatant who, having laid down his arms or having no longer means
of defence, has surrendered at discretion;
(vii) Making improper use of a flag of truce, of the flag or of the military insignia and uniform of
the enemy or of the United Nations, as well as of the distinctive emblems of the Geneva
Conventions, resulting in death or serious personal injury;
(viii) The transfer, directly or indirectly, by the Occupying Power of parts of its own civilian
population into the territory it occupies, or the deportation or transfer of all or parts of the population
of the occupied territory within or outside this territory;
(ix) Intentionally directing attacks against buildings dedicated to religion, education, art, science or
charitable purposes, historic monuments, hospitals and places where the sick and wounded are
collected, provided they are not military objectives;
(x) Subjecting persons who are in the power of an adverse party to physical mutilation or to medical
or scientific experiments of any kind which are neither justified by the medical, dental or hospital
treatment of the person concerned nor carried out in his or her interest, and which cause death to or
seriously endanger the health of such person or persons;
(xi) Killing or wounding treacherously individuals belonging to the hostile nation or army;
(xii) Declaring that no quarter will be given;
(xiii) Destroying or seizing the enemy’s property unless such destruction or seizure be imperatively
demanded by the necessities of war;
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(xiv) Declaring abolished, suspended or inadmissible in a court of law the rights and actions of the
nationals of the hostile party;
(xv) Compelling the nationals of the hostile party to take part in the operations of war directed
against their own country, even if they were in the belligerent’s service before the commencement
of the war;
(xvi) Pillaging a town or place, even when taken by assault;
(xvii) Employing poison or poisoned weapons;
(xviii) Employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or
devices;
(xix) Employing bullets which expand or flatten easily in the human body, such as bullets with a
hard envelope which does not entirely cover the core or is pierced with incisions;
(xx) Employing weapons, projectiles and material and methods of warfare which are of a nature to
cause superfluous injury or unnecessary suffering or which are inherently indiscriminate in violation
of the international law of armed conflict, provided that such weapons, projectiles and material and
methods of warfare are the subject of a comprehensive prohibition [to be set forth in an annex];
(xxi) Committing outrages upon personal dignity, in particular humiliating and degrading treatment;
(xxii) Committing rape, sexual slavery, enforced prostitution, forced pregnancy, … enforced
sterilization, or any other form of sexual violence also constituting a grave breach of the Geneva
Conventions;
(xxiii) Utilizing the presence of a civilian or other protected person to render certain points, areas or
military forces immune from military operations;
(xxiv) Intentionally directing attacks against buildings, material, medical units and transport, and
personnel using the distinctive emblems of the Geneva Conventions in conformity with international
law;
(xxv) Intentionally using starvation of civilians as a method of warfare by depriving them of objects
indispensable to their survival, including wilfully impeding relief supplies as provided for under the
Geneva Conventions;
(xxvi) Conscripting or enlisting children under the age of fifteen years into the national armed forces
or using them to participate actively in hostilities.
For more information about these war crimes, see the ICC list of elements of crimes.
Author Information
Jennifer K. Elsea
Legislative Attorney
Disclaimer
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This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
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