War crime | History, Examples, & International Rules (2024)

war crime, in international law, serious violation of the laws or customs of war as defined by international customary law and international treaties.

Definition and conceptual development

The term war crime has been difficult to define with precision, and its usage has evolved constantly, particularly since the end of World War I. The first systematic attempt to define a broad range of war crimes was the Instructions for the Government of Armies of the United States in the Field—also known as the “Lieber Code” after its main author, Francis Lieber—which was issued by U.S. Pres. Abraham Lincoln during the American Civil War and distributed among Union military personnel in 1863. For example, the Lieber Code held that it was a “serious breach of the law of war to force the subjects of the enemy into service for the victorious government” and prohibited “wanton violence committed against persons in the invaded country,” including rape, maiming, and murder, all of which carried the penalty of death. More recently, definitions of war crimes have been codified in international statutes, such as those creating the International Criminal Court and the war crimes tribunals in Yugoslavia and Rwanda, for use in international war crimes tribunals. In contrast to earlier definitions, modern definitions are more expansive and criminalize certain behaviours committed by civilians as well as by military personnel.

Immediately following World War I, the victorious Allied powers convened a special Commission on the Responsibility of the Authors of the War and on Enforcement of Penalties. The commission’s report recommended that war crimes trials be conducted before the victors’ national courts and, when appropriate, before an inter-Allied tribunal. The Allies prepared an initial list of about 900 suspected war criminals and submitted the list to Germany. Although heads of state traditionally had enjoyed immunity from prosecution, the commission’s main target was Germany’s Emperor (Kaiser) William II, whom most of the Allies (though not the United States) wished to hold responsible for numerous violations of the laws of war. William, however, took refuge in the Netherlands, which refused to extradite him, and he was never tried. Most of the remaining suspected war criminals on the list similarly managed to avoid prosecution, because Germany was reluctant to turn them over to the Allies. Instead, a compromise was reached whereby the Allies permitted a small number of suspects to be tried in Germany before the Supreme Court in Leipzig. These prosecutions resulted in few convictions, with most sentences ranging from a few months to four years in prison.

The Nürnberg and Tokyo trials

The next major attempt to prosecute war criminals occurred in Europe and Asia after World War II. Throughout the war, the Allies had cited atrocities committed by the Nazi regime of Adolf Hitler and announced their intention to punish those guilty of war crimes. The Moscow Declaration of 1943, issued by the United States, Great Britain, and the Soviet Union, and the Potsdam Declaration of 1945, issued by the United States, Great Britain, and China (and later adhered to by the Soviet Union), addressed the issue of punishing war crimes committed by the German and Japanese governments, respectively.

At the war’s conclusion, representatives of the United States, the United Kingdom, the Soviet Union, and the provisional government of France signed the London Agreement, which provided for an international military tribunal to try major Axis war criminals whose offenses did not take place in specific geographic locations. This agreement was supported by 19 other governments and included the Nürnberg Charter, which established the Nürnberg tribunal and categorized the offenses within its jurisdiction. The charter listed three categories of crime: (1) crimes against peace, which involved the preparation and initiation of a war of aggression, (2) war crimes (or “conventional war crimes”), which included murder, ill treatment, and deportation, and (3) crimes against humanity, which included political, racial, and religious persecution of civilians. This last category included what is commonly called genocide.

The term genocide was coined by the Polish American legal scholar Raphael Lemkin and first appeared in print in his work Axis Rule in Occupied Europe: Laws of Occupation, Analysis of Government, Proposals for Redress (1944). The Convention on the Prevention and Punishment of the Crime of Genocide, adopted by the General Assembly of the United Nations in 1948, defined genocide as including killing or inflicting serious physical or mental injury on members of a national, ethnic, racial, or religious group with the intention of bringing about the group’s destruction, in whole or in part. The convention made genocide an international crime that could be prosecuted in the court of any country. Because the Nürnberg trials preceded the convention, however, Nazi war criminals were not prosecuted for genocide.

The International Military Tribunal in Nürnberg, Germany, tried 22 Nazi leaders, including one, Martin Bormann, who was tried in absentia. The trial was conducted in four languages and lasted nearly 11 months. All but three of the defendants were convicted; 12 were sentenced to death. The remaining defendants received lengthy prison terms, which they served at Spandau Prison in West Berlin. Subsequent trials were held under the auspices of Control Council Law No. 10, which was used to prosecute accused Nazi war criminals whose crimes took place in specific locales.

Japanese defendants accused of war crimes were tried by the International Military Tribunal for the Far East, which was established by a charter issued by U.S. Army Gen. Douglas MacArthur. The so-called Tokyo Charter closely followed the Nürnberg Charter. The trials were conducted in English and Japanese and lasted nearly two years. Of the 25 Japanese defendants (all of whom were convicted), 7 were sentenced to hang, 16 were given life imprisonment, and 2 were sentenced to lesser terms. Except for those who died early of natural causes in prison, none of the imprisoned Japanese war criminals served a life sentence. Instead, by 1958 the remaining prisoners had been either pardoned or paroled.

From their outset, the war crimes trials were dismissed by critics merely as “victor’s justice,” because only individuals from defeated countries were prosecuted and because the defendants were charged with acts that allegedly had not been criminal when committed. In support of the trials, the Nürnberg tribunal cited the Kellogg-Briand Pact (1928), which formally outlawed war and made the initiation of war a crime for which individuals could be prosecuted.