During World War II, the Allies committed legally proven war crimes and violations of the laws of war against either civilians or military personnel of the Axis powers. At the end of World War II, many trials of Axis war criminals took place, most famously the Nuremberg Trials and Tokyo Trials. In Europe, these tribunals were set up under the authority of the London Charter, which only considered allegations of war crimes committed by people who acted in the interests of the Axis powers. Some war crimes involving Allied personnel were investigated by the Allied powers and led in some instances to courts-martial. Some incidents alleged by historians to have been crimes under the law of war in operation at the time were, for a variety of reasons, not investigated by the Allied powers during the war, or were investigated but not prosecuted.

The Abbeville massacre took place during the Battle of France in the French town of Abbeville on 20 May 1940. 21 political prisoners, mainly foreign nationals, were killed by the French soldiers who feared that they might become possible fifth columnists or collaborators with Nazi Germany.