War Crimes: History, Basic Concepts, and Structures

Ukraine’s prosecutor general, Iryna Venediktova, announced that the government had evidence of “over 13,000” war crimes committed by invading Russian troops. In Russia, prosecutors announced that war crimes trials of captured Ukrainians would also take place, pointing particularly to the more than 1,900 Ukrainian fighters who had surrendered from the Azovstal steel plant in Mariupol. Experts worried that the Russian justice system, under strong state control, could result in show trials for soldiers accused of being “Nazis” by Vladimir Putin. Those fears appear to be confirmed with death sentences imposed on two British nationals fighting with the Ukrainian army in June, who should have been treated as prisoners of war.

Stories of war crimes, sadly, have become an almost daily occurrence in global news outlets, as have broader questions of criminal responsibility in that conflict. Could Russia’s military leadership, indeed Vladimir Putin himself, for example, face charges or trial for war crimes? If so, where? Are all war crimes trials merely glorified show trials? Many have suggested that Russia’s military and civilian government leaders may be guilty of the most serious of war crimes: genocide, crimes against humanity, or waging aggressive war. Pundits abound.

For many in the United States, even experienced lawyers working in the criminal justice system, war crimes are a different animal, something seldom prosecuted in the United States, and certainly not familiar terrain for most prosecutors and defense counsel, let alone judges. This article will attempt to give shape to some of the basic concepts involved in the history and evolving structures of war crimes prosecutions. It does not pretend to be a comprehensive guide to all war crimes; such a task is far beyond the scope of this work. Indeed, scholars have filled volumes on the nature of war crimes and the issues involved in accountability for them. Instead, it will introduce some basic concepts and structures, with examples as guidance. It is not a comprehensive catalog of all available offenses in domestic or international law, or of the defenses that can be raised against such charges. Because this is an area increasingly addressed by international law and institutions, the article will also address broader questions such as how international humanitarian law—the law of war—comes into play, and whether war itself is legal. The latter is a question we seldom ask anymore, but it should always be somewhere in legal and political discussions. States as well as individuals can be legally responsible for aggressive war, and, in international law, tribunals can ascertain both individual and state responsibility.

What Are War Crimes?

The very idea that war can produce criminal liability seems somewhat anomalous. Ancient rules permitted, indeed applauded, the killing or wounding of legitimate opponents in war, as well the destruction, occupation, or seizure of physical military objectives. In times of peace, these acts would be crimes of murder, assault, destruction of property, or other serious offenses. However, in wartime, the principle of combatant immunity provides such actions with a cloak of protection. But the immunity is not unlimited. Telford Taylor, one of the Nuremberg prosecutors and author of the modern classic Nuremberg and Vietnam: An American Tragedy (1970), argues that the term “war crime” is a misnomer, “for it means an act that remains criminal even though committed in the course of war, because it lies outside the area of immunity prescribed by the laws of war.” Id. at 20. This article will not explore the more complex questions of what constitutes an armed conflict, when conflicts begin or end, or what constitutes an occupying or neutral power. However, it will offer brief analysis of each of the four categories of crimes in war that are most recognized today: war crimes, crimes against humanity, genocide, and aggressive war, or crimes against peace.

War Crimes. The most significant and fullest articulation of what constitute war crimes came with the Nuremberg trials after World War II—about which more below—and the adoption of the four Geneva Conventions in 1949, together with their Additional Protocols in 1977. In 1949, the International Committee of the Red Cross (ICRC), which has led the way on the systematic development of the law of war, set out the four Geneva Conventions, which deal with a wide range of topics but focus most heavily on the protection of civilian populations and prisoners of war. They are about how war is conducted, not whether and how to go to war at all. They are now universally adopted treaties—the United States has long been a party to them—and they use the term “grave breaches” to refer to what constitutes commission of a war crime. The list is long, but representative examples include the willful killing of protected civilians or legitimate prisoners of war; torture or inhuman treatment, including biological experiments; the taking of hostages; extensive destruction of property not justified by military necessity; and willfully depriving a prisoner of war of the right to a fair and regularly constituted trial. Other international treaties, adopted as the Hague Conventions, deal with the means and methods of war and forbid the use of poison or poisonous weapons, the use of weapons calculated to cause unnecessary suffering, pillage, and bombardment of undefended buildings, villages, or towns, among other limitations. Together, these two bodies of treaty law give shape to most domestic and international definitions of war crimes: crimes committed during war and crimes using prohibited means.

Perhaps the most significant limitation on contemporary prosecution of war crimes, whether in the United States or elsewhere, is the inherent limitations of international humanitarian law. The Geneva Conventions, by their terms, apply overwhelmingly to international armed conflicts. Those are traditional wars between countries, such as the armed conflict between Russia and Ukraine. Such wars, however, are increasingly rare in contemporary history; most armed conflicts in recent decades are either what we call civil wars, wars that involve a state with some non-state actor, such as a rebel or insurgent force, or conflicts involving the various terrorist groups now operating on both a local and global level. For those “non-international” armed conflicts, as the Geneva Conventions call them, the formal rules are much more limited.

The most explicit provisions on non-international armed conflicts are in Common Article 3, a single provision that appears in identical form in each of the four Geneva Conventions. Those provisions provide more limited protections in non-international armed conflicts than those amply delineated in the Conventions. The US Supreme Court famously found that Common Article 3 applied to protect prisoners at Guantanamo Bay, in Hamdan v. Rumsfeld, 548 U.S. 557 (2006). The Court rejected arguments that, as what the government called nonprivileged enemy combatants, the detainees enjoyed no protection under the laws of armed conflict. Additional Protocol 2 to the Geneva Conventions, adopted in 1977, deals more fully with non-international armed conflicts. The United States, however, has not ratified that treaty. The ICRC argues that most provisions relating to international armed conflict also apply to internal conflicts by means of customary international law—the actual established practice of nations—but that position, too, is controversial and not accepted by the United States.

Crimes Against Humanity. Both this category and the next, genocide, are crimes of mass atrocity. Crimes against humanity first appeared in codified form as part of the Nuremberg Charter, with its further provisions for an International Military Tribunal, in article 6(c). It was included to cover

murder, extermination, enslavement, deportation, and other inhumane acts committed against any civilian population, before or during the war, or persecutions on political, racial or religious grounds in execution of or in connection with any crime within the jurisdiction of the Tribunal, whether or not in violation of the domestic law of the country where perpetrated.

A similar provision was included for the Tokyo trials but did not play as important a role there. The Nuremberg provision was designed to reach issues that traditional war crimes could not, issues that were the defining features of the Nazi regime, particularly persecution of Jews and the ensuing Holocaust. Modern versions of the crime have expanded its scope to include rape and torture and have included language that the offending acts be committed “as part of a widespread or systematic attack directed against any civilian population.”

Genocide. The crime of genocide famously came into being through the efforts of a Polish jurist, Rafael Lemkin, who developed the idea of acts directed not at persons, in their individual capacity, as with crimes against humanity, but acts directed at the destruction of groups. Genocide, too, was discussed at Nuremberg, and even appeared briefly in the indictments and oral arguments, but was not included among the crimes charged or eventual verdicts. The crime came into being through the adoption of the first modern human rights treaty, the Convention on the Prevention and Punishment of the Crime of Genocide, adopted by the UN in 1948. The Convention, in its article II, included a definition of genocide that has largely stood the test of time: “acts committed with intent to destroy, in whole or part, a national, ethnical, racial or religious group,” by such means as killing or serious bodily or mental harm, measures to prevent births, forcibly transferring children to another group, or inflicting conditions to bring about the group’s destruction.

Philippe Sands, a British barrister and law professor, recently wrote a poignant and eloquent book, East West Street (2016), that documents the origins of the offenses of crimes against humanity and genocide. He links the history of his own ancestors with that of Hersch Lauterpacht and Rafael Lemkin, all Jews from the same town of what is now Lviv, in western Ukraine, who shaped the concepts. He notes that an “informal hierarchy” has developed in which genocide has evolved into the “crime of crimes,” whereby politicians and activists use the word to evoke the worst possible crime. That status may move prosecutors to charge the crime, when, in his view, it is harder to prove than crimes against humanity. Id. at 364. This may explain in part why US politicians are so reluctant to invoke the term for mass crimes committed outside of the United States, and why both Russia and Ukraine have charged genocide, Russia to justify its invasion, and Ukraine to describe the devastation wrought by the Russians in its territory. It is also noteworthy that the first modern conviction for genocide did not occur until 1998, with the conviction for that crime of Jean-Paul Akayesu, a former teacher and mayor of a small community in Rwanda, during the 1994 genocidal rampage in that country. Prosecutor v. Akayesu, ICTR Judgment (Sept. 2, 1998).

Aggression. The crime of aggression was intended to be the centerpiece of the Nuremberg prosecutions. It was hoped that all defendants would be found guilty of waging aggressive war, there called “crimes against the peace.” Eventually, 12 of the 21 defendants in the courtroom were convicted of that crime, while most were convicted of crimes against humanity. Aggression is particularly challenging in law because it easily slips into the moral terrain of which wars are “just” and which are “unjust,” a question that has plagued theologians and experts for centuries. One must decide if armed intervention in another’s territory is justified or unjustified, provoked or merely defensive. The Nuremberg Charter defined crimes against the peace as:

planning, preparation, initiation or waging of a war of aggression, or a war in violation of international treaties, agreements or assurances, or participation in a common plan or conspiracy for the accomplishment of any of the foregoing.

Charter of the Int’l Military Tribunal, art. 6(a). The definition leaves open what exactly is “a war of aggression,” though the judges of the Tribunal had no difficulty in finding guilt for what they considered, in an oft-quoted passage of their 1946 judgment, to be “the supreme international crime” because “it contains within itself the accumulated evil of the whole.” Current debates about the existence and definition of the crime of aggression are developed below.

War Crimes Prosecutions in US History

US law on war crimes is both old and new, both domestic and international. Trials of war crimes in the United States have traditionally been carried out in military tribunals, via courts martial or military commission. During the Civil War, President Lincoln adopted General Order No. 100, a document prepared by a German immigrant and veteran of European wars, Francis Lieber, who became a professor of the new field of law of war at Columbia University. The “Lieber Code” included provisions for punishment of war crimes and was the basis for the prosecution of Mary Surratt and others following President Lincoln’s assassination.

One reason so little is known about war crimes here in the United States is because war crimes prosecutions are so rare. The United States adopted a War Crimes Act (18 U.S.C. § 2441) in 1996, during the Clinton administration. That act defines war crimes as any of the “grave breaches” of the Geneva Conventions noted above, and others, and certain provisions of the Hague Conventions. There has never been a prosecution under the act. The statute follows the traditional list of what constitutes a war crime and limits application to US nationals who are involved as either perpetrators or victims. It does not allow for universal jurisdiction, which would give authority to US courts to hear evidence of certain serious war crimes against an accused within US jurisdiction, wherever in the world and whenever that offense may have been committed.

This is not to say that the United States does not have other means to address war crimes. The Departments of Justice (DOJ) and Homeland Security each have units that deal with war crimes violations. In DOJ, the Criminal Division has a Human Rights and Special Prosecutions Section, while in DHS, Immigration and Customs Enforcement (ICE) runs a Human Rights Violators & War Crimes Center. The DOJ program deals with war crimes and other violations of human rights, while the ICE program enforces immigration laws barring the entry of war criminals into the United States, and deporting those who enter illegally as war criminals. However, war crimes trials within the United States are still unusual.

Telford Taylor points to early war crimes trials during the American Revolution, during which both Captain Nathan Hale and British Major John André were convicted of spying and hanged. Taylor, Nuremberg and Vietnam, supra, at 21. A book-length global bibliography on war crimes, published in 1986, touches on a few of the other most significant war crimes trials in US history. They are as noteworthy for their rarity as for their notoriety. One of the earliest trials for war crimes included in the bibliography occurred after the Civil War, when Confederate Captain Henry Wirz was tried in 1865 for war crimes. He was convicted and hung for his role as administrator of the Andersonville Prison in Georgia. The book documents wide reports of war crimes by US troops in the Korean conflict (1950–53), mostly during air attacks, but no one was charged. N.E. Tuterow, War Crimes, War Criminals, and War Crimes Trials—An Annotated Bibliography and Source Book (1986).

A conspicuous oversight in the book is its failure to mention anything about war crimes trials arising from the relentless campaign by the US military against Native American populations, particularly in the last decades of the 19th century. No mention is made, for example, of the trial of 392 Dakota men for war crimes after their surrender in the Dakota War of 1862. Those trials, lasting only days and profoundly lacking in any due process, resulted in the conviction and death sentences for 303 of the Native Americans. President Lincoln commuted all but 39 sentences, and 38 of those men were hanged for their crimes. Another famous trial was that of the 20-year-old Brulé Sioux man, Tasunka Ota, known as Plenty Horses, in South Dakota in 1891. He shot and killed Lieutenant Edward Casey, a Seventh Cavalry soldier who had ridden into a tribal gathering to explore diplomatic solutions to an ongoing conflict. Plenty Horses’ defense counsel argued that the Sioux were at war with the United States, and since both men were soldiers, the killing was not murder. Plenty Horses had been held by the US Army as a prisoner of war, thus recognizing his status as a combatant, and a jury had no problem acquitting him of the charges based on the combatant’s privilege.

Yet another oversight in the bibliography was the World War II trial, in the United States, of eight German soldiers, all of whom had entered the United States clandestinely by submarine in 1942 to carry out acts of sabotage. All wore uniforms at the time they came ashore, presumably so they could later claim combatant status. They were quickly captured and later tried by military commission as spies and war criminals. All were convicted and sentenced to death. Their unsuccessful appeal to the US Supreme Court is reported in Ex Parte Quirin, 371 U.S. 1 (1942); all were soon executed. Lieutenant Colonel Kenneth Royale ably conducted their defense at trial and on appeal, and later became the last Secretary of War, serving under President Truman until forced into retirement for his unwillingness to enforce or carry out Truman’s executive order to desegregate the military.

A much more contemporary example comes from the conflict in Iraq, during the Battle of Mosul in 2017. Navy SEAL Eddie Gallagher was charged with the serious war crime of killing a captured enemy soldier, a 17-year-old ISIS fighter in military custody. The case was unusual because it was Gallagher’s own men who reported what they saw as his erratic and possibly illegal behavior. After his conviction by court martial and subsequent demotion, President Donald Trump intervened, reversed the demotion, and restored Gallagher’s Trident Pin, the SEAL emblem. He later granted Gallagher clemency despite severe criticism from military leaders.

Without a doubt, however, the best remembered and most notorious of US war crimes trials in contemporary history arose from events in March of 1968, in My Lai, a hamlet in Quang Ngai province in South Vietnam. There, US soldiers, acting on orders from superiors to destroy a Viet Cong enclave (subsequently shown to be mistaken), killed more than 500 unarmed civilian men, women, and children, essentially the entire village. Some women, one as young as 12, were gang-raped before their murders. Twenty-six soldiers were charged, but one soldier, Lieutenant William Calley, became the focus of blame, and his trial for war crimes made international news. It also gave increasing momentum to both accountability of US leadership and the ending of the Vietnam conflict. Subsequent publication of the Pentagon Papers in The New York Times in 1967 also revealed the depths of US disinformation about the war. The My Lai incident left an indelible mark on the actions of the US military in that war. No other superior officer was ever tried, and Calley himself, though initially sentenced to life imprisonment at hard labor, eventually served only three years of house arrest. The events in My Lai also garnered intense focus within the academic community, giving rise to an acerbic volume called Crimes of War, published in 1971 in the wake of the massacre.

Most recently, some have called for war crimes prosecutions of US leaders following the initially secret detention, starting in 2002, of more than 770 suspected terrorists at Guantanamo Bay following the attacks of September 11, 2001. The US government has released or repatriated all but 37 of the detainees, and only eight have been convicted of any crime. Many of the detainees were interrogated under torture in “black sites” or otherwise mistreated. The US invasion of Iraq in 2003, based on spurious evidence of the existence of weapons of mass destruction, again drew calls by some experts for prosecution of leaders, with massive peace marches taking place in Europe and the United States, calling for the end of the conflict. Iraqi leader Saddam Hussein, captured in ignominious circumstances, stood trial in Iraq for crimes against humanity and was convicted and executed.

International War Crimes Prosecutions

Although the US experience with war crimes is somewhat limited, international war crimes prosecutions, though relatively recent, are significantly more developed. Again, this is not to give primacy to international prosecutions; there are many who believe that only states should conduct war crimes prosecutions. This section will explore the issue of war crimes at the international level, with focus on the landmark post–World War II trials; the ad hoc international criminal tribunals in the former Yugoslavia and Rwanda; the International Criminal Court; the International Court of Justice. and the European Court of Human Rights.

War Crimes Trials After the World Wars. The trial of wartime leaders is relatively new to history. Napoleon was exiled—twice—rather than standing trial for possible war crimes. After World War I, there were calls for accountability of German leadership. The Treaty of Versailles contained a provision “arraigning” Kaiser Wilhelm II of Germany for his offenses against “international morality” and the “sanctity of treaties,” without any formal legal charge. The Dutch government, where he had fled, refused his release to the Allies and granted him asylum in the Netherlands, where he lived out his life. After World War II, many leaders within the Allied forces, including Churchill, called for summary execution of the captured Nazi leadership. Instead, the Allied powers—Russia, Great Britain, France, and the United States—adopted the Nuremberg Charter and its accompanying Charter of the International Military Tribunal, leading to war crimes trials in that German city in 1946. General Douglas MacArthur adopted a similar charter for the later Tokyo war crimes trials in Japan.

The best known of the Nuremberg trials is the International Military Tribunal (IMT), which tried the Nazi leadership in 1945–46 before a tribunal made up of four judges and four alternates, two each from the Allied countries of Russia, the United Kingdom, France, and the United States. Alternates sat through the trial and took part in the judgment. Of the 24 Nazi leaders charged, 21 well-known if infamous individuals appeared in the dock for trial. Martin Bormann was tried in absentia. The defendants included Hermann Göring, Rudolph Hess, Albert Speer, and other notorious leaders of the Reich. Members of the group faced three categories of charges: traditional war crimes, crimes against humanity, and crimes against peace—the waging of aggressive war. The latter two categories were new, but prosecutors argued that they were well grounded in prior treaties or the customary law of nations, which allowed prosecutors to avoid ex post facto claims, but have been part of the lasting critique of that trial.

Robert Jackson, on leave from the US Supreme Court, served as US chief counsel at the Tribunal. The IMT trial opened on November 20, 1945, and, after 403 sessions held over 216 days, the Tribunal delivered its verdict on October 1, 1946. Often overlooked in the process is the trial and conviction of criminal organizations within the Nazi hierarchy. The tribunal found the Nazi leadership; the Gestapo; the SS, a paramilitary security organization; and the SD, the intelligence agency of the SS, to be culpable as organizations. Of the individual defendants, 12 were convicted of engaging in aggressive war while only two of the defendants were found not guilty of war crimes or crimes against humanity. Ten of the defendants were hanged, seven were sentenced to prison terms, and three were acquitted. Göring committed suicide before his execution.

Lesser known, but important to development of the law on war crimes, are the Nuremberg Military Tribunals, or Subsequent Trials, which took place under US aegis from 1946 through 1949. These 12 trials, under Control Council Law No. 10, grouped various Nazi elements for trial, including, for example, doctors, industrialists, judges, and the Einsatzgrupen, or mobile SS death squads. Those trials, together, provided a solid groundwork for future war crimes prosecutions. It would be several decades before the international community had the will to create new tribunals with jurisdiction over war crimes. However, this is not to suggest that there were not war crimes prosecutions at the domestic level. After World War II, there were hundreds of prosecutions in various countries of Europe for war crimes and related offenses, and many countries have brought war crimes charges within the domestic regime since.

In the historical shadows of their European counterparts, the Japanese war leadership also stood trial for their war crimes—minus Emperor Hirohito, who retained his throne in the face of strong criticisms that he too should be in the dock. Much of what happened in Tokyo at the International Military Tribunal for the Far East (IMTFE) replicated the structures of the Nuremberg IMT. The tribunal used the same structure for its charges, and roughly the same number of defendants stood in the dock: 28. Many countries were involved in discussions about that structure, unlike the four major powers in Europe. They included Australia, Canada, China, France, India, the Netherlands, New Zealand, the Philippines, the Soviet Union, the United Kingdom, and the United States. Overall design and operation of the IMFTE finely rested solely in the hands of General Douglas MacArthur, Supreme Commander of the Allied Powers. The charter for the tribunal came out on January 19, 1946, and required that anyone standing trial be charged with crimes against the peace. The 11 judges of the Tribunal came from the Allied Powers: one each from the United States, France, Philippines, China, Canada, New Zealand, India, United Kingdom, Netherlands, the Soviet Union, and Australia.

The trial lasted for over two years, from May of 1946 through November of 1948. It heard testimony from 419 witnesses, with 4,336 pieces of evidence. Many former US POWs testified to atrocities during their detention. The best known of the defendants, most of whom were military leaders, was probably Hideki Tojo, a general in the Imperial Japanese Army and prime minister for much of the war. The final opinion of the judges ran to 1,500 pages; all defendants were found guilty, with dissents issued by three of the judges. One of the defendants was acquitted by virtue of his mental unfitness, and two defendants died during the proceedings. Six defendants, including General Tojo, received death sentences for war crimes, crimes against humanity, and crimes against peace. Another was sentenced to death for war crimes and crimes against humanity. All of those defendants were hanged in 1948. The others received sentences ranging from life imprisonment to a term of years. Like Nuremberg, there were many “subsequent” war crimes trials in the Far East, although they were carried out by many governments in the region rather than the United States. The last ended in 1951; more than 5,500 individuals were tried and convicted, and many were executed.

Defenses in the international tribunals remain largely the same now as they did then. The classic “Nuremberg defense” of superior orders is probably the most common and was explicitly excluded in the Nuremberg Charter’s article 8. Another common defense, particularly in the early days of war crimes trials, was nullum crimen sine lege, the ex post facto argument. Prosecutors went to great lengths to prove the provenance of various newly codified crimes of war, but some still argue that the early trials had no proper basis in law. Other common defenses include necessity, combatant’s privilege, head-of-state immunity, or amnesty. Finally, the tu quoque defense is unique to war. It argues, as the name implies, that “you too” did the offense, arguing that if one side breaches the law, the other’s breach on the same grounds is justified. German Admiral Karl Dönitz, who also served as head of state of Germany briefly after Hitler’s suicide, was one of the Nuremberg defendants. He was charged with the war crime of waging unrestricted submarine warfare. It alleged the sinking of merchant ships and freighters without warning and the shooting of survivors in the water. He was found not guilty because of similar orders having been issued early in the war by the Allied powers. The defense was definitively rejected as “flawed in principle” in Prosecutor v. Kupreskic, ICTY, Judgment of Jan. 14, 2000.

Israel’s trial of Adolph Eichmann also deserves mention here because of its international celebrity then and now. In 1960, Israeli agents successfully kidnapped Eichmann from his anonymous and hidden redoubt in Argentina, a country that became a haven for many fleeing Nazis, and which was not likely to extradite the general, who had been one of the principal authors and administrators, in 1942, of the “final solution” for extermination of Europe’s Jews. Eichmann was convicted of 15 counts of war crimes and crimes against humanity, and he was hanged on May 31, 1962.

New life came to domestic prosecutions for war crimes with the emergence of expanded use of universal jurisdiction. In October of 1998, while seeking medical treatment in England, Chilean dictator Augusto Pinochet was put under house arrest on an international warrant issued by Spanish judge Baltasar Garzón. The judge charged Pinochet with crimes against humanity, grounded in extensive claims of torture. Garzón based his actions on his court’s universal jurisdiction, which permitted him to charge the most serious crimes, committed anywhere in the world and without a statute of limitations, so long as the defendant could be apprehended by judicial order. The House of Lords, then the highest court in Britain, struggled with the issue for nearly two years, ultimately ruling that Pinochet was not immune from prosecution as a head of state. His extradition to Spain failed, however, when UK Home Secretary Jack Straw ruled that Pinochet was too ill to stand trial. He returned to Chile, whose judges revived interest in trying the leader for his acts of terror; ultimately, he died there in disgrace, much of his ill-gotten fortune seized by courts. The innovative use of universal jurisdiction gave rise to a veritable cascade of charges under that norm by domestic courts, primarily in Europe. As recently as January of 2022, for example, a German court found Anwar Raslan, a 58-year-old former intelligence officer from Syria, guilty of crimes against humanity involving torture, killing, rape, and sexual abuse under his direction. The crimes took place in the notorious Al Khatib unit in Damascus, where Raslan had worked until he immigrated to Germany. He was sentenced to life imprisonment.

Ad Hoc and Hybrid Tribunals. As the Cold War began to wane, the UN took action in two important instances, creating “ad hoc” tribunals, designed to address war crimes and other offenses committed in the specific countries in question within a specific timeframe. In 1993, the UN established an International Criminal Tribunal for the Former Yugoslavia, headquartered in The Hague, Netherlands, to address widespread claims of what was referred to as “ethnic cleansing,” during the breakup of Yugoslavia, carried out by Serbs and Croats against the Muslim populations of Bosnia-Herzegovina. The charges included systematic sexual violence against women and genocide. In 1994, the UN again acted to create an ad hoc International Criminal Tribunal for Rwanda, to be headquartered in Arusha, Tanzania. Again, that tribunal dealt with the mass killing of some 800,000 ethnic Tutsi civilians by the majority-population Hutus and other crimes committed in that year. Both tribunals carried out their missions with more sharply defined definitions of war crimes, crimes against humanity, and genocide, and resulted in hundreds of convictions. The UN has played a role in the creation of several other ad hoc or “hybrid” tribunals in Cambodia, Sierra Leone, East Timor, Lebanon, and Kosovo, sometimes combining international and domestic elements to bring about accountability.

The International Criminal Court. The next major step in international prosecution of war crimes occurred in 1998 with the creation of the International Criminal Court (ICC), which sits in The Hague. It should be noted at the outset that the ICC was not set up as a “final court of appeal” in international criminal matters, but as a compliment to domestic jurisdiction, in cases where a country is unable or unwilling to act to punish criminal conduct occurring in the international realm. Grounded in the Rome Statute setting up its jurisdictional scope and structures, the Court now has 123 States Parties, with another 31 states that have signed but not ratified the Statute. Of the 41 states that have neither signed nor ratified, China and India are conspicuous in their absence and their ongoing criticisms of the Court. In addition, the United States and Russia, both of which initially signed the treaty, effectively withdrew all participation with the Court. The Trump administration went so far as to impose sanctions against its chief prosecutor when there was discussion of US accountability for war crimes in Afghanistan. Since the invasion of Ukraine by Russia, however, the Senate, in a unanimous resolution proposed by Senator Lindsey Graham (R-SC), urged “member states to petition the ICC or other appropriate international tribunal to take any appropriate steps to investigate war crimes and crimes against humanity” by Vladimir Putin and others in Ukraine. Press Release, Off. of Sen. Lindsey Graham (Mar. 15, 2022).

The ambit of the ICC is broader than war crimes and other offenses during armed conflict but continues to follow the time-honored structures for crimes committed during armed conflict: war crimes, crimes against humanity, genocide, and, most recently, the revival of the crime of aggression, sometimes called the crime against peace. The addition of the crime of aggression was—and is—one of the most controversial decisions to amend the Rome Statute. The amendment took full effect only in 2018, and to date, only 43 countries have ratified those amendments.

Ukraine did accept the limited jurisdiction of the Court in 2013, which allows prosecution by the ICC of crimes against humanity, war crimes, or genocide after February 20, 2014. Many have called for prosecution of Vladimir Putin and others for various war crimes, and the ICC is actively carrying out investigations, with the cooperation of many countries, into possible international crimes carried out in Ukraine. However, Ukraine’s acceptance of jurisdiction does not include the most recent amendments relating to aggression. The definition of aggression, moreover, is very narrow. The amendment includes only “the planning, preparation, initiation or execution, by a person in a position effectively to exercise control over or to direct the political or military action of a State, of an act of aggression” that violates of the Charter of the United Nations. Rome Statute, art. 8 bis (1) (2010). Thus, the ICC limits prosecution of aggression to the leader of a state who has the power to determine that state’s policies. Whether such jurisdiction extends beyond Putin himself is the subject of many current academic and activist debates.

The International Court of Justice. The ICJ, sometimes called the “World Court,” is one of the oldest international tribunals still in operation, founded in conjunction with the United Nations in 1945. It is the principal judicial organ of the United Nations, and its 15 judges sit in an imposing building in The Hague called the Peace Palace. It is often overlooked as a tribunal that deals with war crimes, insofar as its jurisdiction is primarily limited to disputes between states and the issuance of advisory opinions on specific and limited legal questions. It has, however, dealt with a broad range of issues relating to armed conflict over its history, including, for example, genocide in Bosnia-Herzegovina, the legality of the threat or use of nuclear weapons, and armed conflict in the Democratic Republic of Congo. Most relevant here are its recent actions, largely overlooked in the press, relating to armed interventions by Russia in Ukraine and the Republic of Georgia.

First, with regard to Ukraine, as recently as March 2022, the ICJ issued what are called provisional measures against Russia after the government of Ukraine had sought their intervention only weeks before, arguing that Russia was violating its obligations to prevent genocide under the 1948 Genocide Convention by invading Ukraine. Russia used the pretext that it was engaging in its “special military operation” to prevent genocide in Ukraine. By a vote of 13 to 2, the Court ordered that Russia “shall immediately suspend the military operations that it commenced on 24 February 2022 in the territory of Ukraine.” Request for the Indication of Provisional Measures (Ukraine v. Russian Fed’n), Order, 2022 16 Mar. General List No. 182 (ICJ), ¶ 86(2) (Mar. 16). The order further stated that the “Parties shall refrain from any action which might aggravate or extend the dispute before the Court or make it more difficult to resolve.” This is standard formulation for an order of provisional measures, which are issued when the court takes up a legal question that will require lengthy litigation. Provisional measures seek to prevent changes on the ground before the court’s final decision on the issue.

The order is noteworthy for three reasons. First, the ICJ acted extremely fast for a body known for its lengthy and deliberate actions—only 18 days from Ukraine’s initial filing on February 27. Russia had failed to appear for oral arguments, though it did submit a written pleading. Second, the court noted that it has the power to indicate provisional measures when “irreparable prejudice could be caused to rights which are the subject of judicial proceedings or when the alleged disregard of such rights may entail irreparable consequences.” Id. ¶ 65. The court’s recognition of the risks of delay is heartening. Third, though the measures are not enforceable, they express the legal views of the international community in the strongest possible terms. The litigation will continue as the fighting in Ukraine continues unabated, at this writing.

The ICJ action against Russia in this case, however, was not its first consideration of a matter involving Russia. That honor goes to a case filed against the Russian Federation in 2008 by Georgia, following Russia’s armed interventions into the regions of South Ossetia and Abkhazia of that country. While those regions had autonomous status during the Soviet era, they had become a part of the Republic of Georgia after the dissolution of the Soviet Union. The action was grounded in alleged violations by Russia of the Convention on the Elimination of Racial Discrimination (CERD), to which both countries are states parties. Georgia sought to protect its citizens from actions by “Russian armed forces, acting in concert with separatist militia and foreign mercenaries” that constituted what was asserted to be ethnic cleansing of Georgians from those territories. The ICJ also issued provisional measures in that case, but ultimately found that it had no jurisdiction to decide the dispute. Application of the International Convention on the Elimination of All Forms of Racial Discrimination (Georgia v. Russian Fed’n), Preliminary Objections, 2011 I.C.J. 70 (Apr. 1). It found that there were no grounds for Georgia’s allegations of racial discrimination, nor was there a basis for intervention by the court under the CERD to decide such an issue.

The European Court of Human Rights. As noted at the outset of this article, the Ukrainian defense lawyer in that country’s first prosecution of a Russian for war crimes indicated that he would take his case, if necessary, to the European Court of Human Rights (ECHR). That human rights tribunal, which has existed in Europe since 1950, is part of the legal structures of the Council of Europe, which now includes 46 member states, a much broader constituency than the European Union, at 27 countries, or even NATO, with 30 member states. Notably, the member states of the Council of Europe include Russia, Ukraine, Georgia, and several other countries that were part of the Soviet Union before its breakup. Russia’s membership was suspended immediately after its invasion of Ukraine, but it remains subject to the ECHR. The court operates within the legal framework of the European Convention on Human Rights and its 16 Protocols, amendments or supplements to it added over the years. Each country elects a judge to the court, and the court operates in panels that vary in size from three to 17. The ECHR is one of three regional human rights systems worldwide, with others in the Americas and Africa. Its judgments are generally honored and respected.

While one normally thinks of human rights law as a field separate and distinct from that of the law of war, the European Court, after avoiding the issue for many years, has played a repeated role in adjudicating human rights issues arising from armed conflicts within its jurisdiction. That change of heart follows on the pioneering work by the Inter-American Commission on Human Rights in application of the law of war by a human rights tribunal, in such cases as Juan Carlos Abella v. Argentina, Case 11.137, Report No. 55/97 (Nov. 18, 1997). While cases at the European Court allege violations of human rights norms embodied in the European Convention, many could constitute war crimes for which the state in question is accountable. Prominent examples of the court’s intervention in armed conflicts within or among its members include that between Turkey, a member state, and the Workers’ Party of Kurdistan, or PKK; the conflict in Bosnia-Herzegovina in the 1990s; the conflicts in the Chechen Republic of the Russian Federation; and even NATO operations in Afghanistan, involving European troops there. Fact Sheet—Armed Conflicts, ECHR (Apr. 2022).

The most significant cases for our purposes are those that involve inter-state complaints, one of the procedural mechanisms established by the court to allow member states in conflict to seek intervention by the tribunal. The court presently has “five inter-State applications lodged by Ukraine against Russia and over 8,500 individual applications concerning the events in Crimea, Eastern Ukraine and the Sea of Azov pending before the Court.” Id. at 20. These cases cover a timeframe from Russia’s first incursions into Crimea in 2014 through to the present. In 2018, the court issued a press release indicating that it would design a systematic way of dealing with the many cases, combining the inter-state mechanism with individual complaints while assuring that domestic jurisdiction was not available prior to seeking review in the court. Press Release, ECHR (Dec. 17, 2018). The court has opened the case for decision and has reiterated its own interim measures (similar to those of the ICJ, above), in language that echoes of concern for war crimes violations.

In a more recent press release, the ECHR spoke to submissions by Ukraine charging violations since the military intervention by Russia in February and asking the court for protection. The court agreed. It imposed interim measures and reiterated earlier ones. They variously ask “the Russian Federation to refrain from military attacks against civilians and civilian objects, including residential premises, emergency vehicles and other specially protected civilian objects such as schools and hospitals, and to ensure immediately the safety of the medical establishments, personnel and emergency vehicles within the territory under attack or siege by Russian troops.” It cautioned that this covered all attacks against civilians, “including with the use of any form of prohibited weapons, measures targeting particular civilians due to their status, as well as the destruction of civilian objects under the control of Russian forces.” Finally, it said that Russia “should ensure unimpeded access of the civilian population to safe evacuation routes, healthcare, food and other essential supplies, rapid and unconstrained passage of humanitarian aid and movement of humanitarian workers.” Press Release, ECHR (Apr. 1, 2022). All of these measures are firmly grounded in principles and norms of humanitarian law, the law of war.

Conclusion—War, What Is It Good for?

In his magisterial work on violence, The Better Angles of Our Nature (2011), Harvard psychology professor Steven Pinker argues that, despite our intuitive sense to the contrary, over history violence has diminished throughout the world, in virtually every way, from fewer wars to not spanking our children. “The belief that [violence] has decreased,” he argues, “suggests that we started off nasty and that the artifices of civilization have moved us in a noble direction, one that we can hope to continue.” Id., preface, at xxi–xxii. Systematic war crimes trials at either the domestic or the international level are a relatively recent phenomenon. Most have occurred from the mid-20th century, after Nuremberg, and today have become relatively common. War, on the other hand, seems depressingly eternal.

As it drags on without respite, the conflict between Russia and Ukraine has given rise to one of the most aggressive investigations of war crimes in history. The International Criminal Court has received requests to begin an investigation by 43 countries. Private organizations and the governments of Poland, France, Germany, and Lithuania have all begun to gather evidence of war crimes among the massive refugee populations who have fled Ukraine to seek protection in those countries. Ukraine’s prosecutor general Venediktova says that Estonia, Latvia, the Czech Republic, and Slovakia are in the process of signing on to cooperate. All of them will collaborate with a team of 42 investigators dispatched from the ICC, its largest investigation in history. Eurojust, the European Union’s agency for judicial cooperation, will establish files of shareable evidence, such as DNA profiles, audio and video recordings, and satellite images. Loveday Morris, Hope for Justice Imbues the Vast Effort to Document War Crimes, Wash. Post, May 29, 2022, at A20. War crimes investigations must be coordinated, but they seem to have reached a level of maturity and sophistication unheard of at the global level.

In 1928, 15 nations, including the Great Powers, attempted to put a stop to war forever with the Kellogg-Briand Pact, sometimes called the Pact of Paris. It was a simply worded treaty that attempted to stop war entirely. The first of its three short articles declared that its signatories “condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy in their relations with one another.” Forty-seven additional nations eventually signed the agreement; the US Senate voted 85-1 to ratify the treaty. Within just over a decade, World War II was under way, causing most academics and diplomats to conclude that the treaty had been relegated to the cynical waste bin of history. Some argue, however, that Kellogg-Briand was the beginning of a new world order in foreign relations, one in which wars are fought less frequently and less intensively, where conquest no longer occurs and empires have disappeared. Oona A. Hathaway & Scott J. Shapiro, The Internationalists (2017). While this article focuses on accountability for war crimes, we should never lose hope that one day there will be no war at all.