There are many reported war crimes committed by Allied military forces in World War II. The armed forces of the Soviet Union, in particular, engaged in the mass killing, deportation, forced labour and mistreatment of prisoners of war and civilians, as well as mass rapes and widespread looting in occupied territories. War crimes were also committed by British, American and other Allied forces, but not on the same scale as those of the Axis powers and the Soviet Union. There has been continued debate over whether the British and American strategic bombing campaigns, in which an estimated 800,000 civilians were killed, were war crimes.

After the war, many trials of Axis war criminals took place, most famously, the Nuremberg trials and Tokyo Trials. However, Allied war crimes were not prosecuted by the post-war international military tribunals. The Western Allies prosecuted a number of war crimes committed by their own forces, but these prosecutions represented only a small proportion of the crimes the Allies probably perpetrated.

In the 21st century, historians and other commentators have paid more attention to Allied war crimes, while warning against arguments suggesting a "moral equivalence" between the actions of the Allies and the crimes of the Axis powers.

Background The military of the major Western Allies the UK, France and United States were directed to adhere to the Hague Conventions and Geneva Conventions. The Soviet Union had not signed these conventions. In August 1945, the Charter of the International Military Tribunal (IMT) defined war crimes as any violation of the customs of war including the deportation, murder or mistreatment of civilians and prisoners of war (POWS) and any plunder or wanton destruction of property or human settlements not justified by military necessity. The IMT charter also defined crimes against humanity to include the extermination, enslavement, deportation, persecution or inhumane treatment of civilians.

Major Allies War crimes were committed by the Western Allied powers, but not on the same scale as those of the Axis powers and the Soviet Union. The Western Allies prosecuted a number of war crimes committed by their own forces, but Allied war crimes were not prosecuted by the post-war international military tribunals.

Allied soldiers in all theatres sometimes killed enemy soldiers who were attempting to surrender or after they had surrendered. This was particularly common on the Eastern Front and in the Asia-Pacific theatre.

There has been continued debate over whether the area bombing of cities in Germany and Japan and the atomic bombing of Hiroshima and Nagasaki were war crimes. Although there was no international treaty or customary law at the time specifically prohibiting the aerial bombardment of civilians, there were general principles of international law which might have applied. Philosopher Douglas P. Lackey argues that the Hague Conventions, which restricted artillery bombardment of undefended cities, could be applied by analogy to aerial bombardment. A. C. Grayling, however, states that "any competent lawyer could easily defend the area-bombing campaign against imputations of having violated its provisions." Eric Markusen and David Kopf argue that the Allied strategic bombing met the IMT definitions of both war crimes and crimes against humanity. However, the issue was not considered at the Nuremberg and Tokyo war crime trials.

Grayling writes that the unclear legal position means that arguments over the Allied bombing of civilians often concern ethical issues. Critics of area bombing have argued that deliberate attacks on civilian populations are a moral crime, whereas defenders of Allied area bombing often argue that it was a military necessity in a total war where the distinction between the enemy military and civilians aiding the war effort was blurred.

Soviet Union

The Soviet Union was responsible for imprisoning, deporting and often massacring hundreds of thousands of civilians and POWs from occupied or annexed territories.Robert Gellately (2007). Lenin, Stalin, and Hitler: The Age of Social Catastrophe. Knopf, pp. 391-396 This included the Katyn massacre of 22,000 Polish officers and intellectuals in 1940 and the Gegenmiao massacre of over 1,000 Japanese women and children in 1945.

The Soviet Union inflicted high death rates on POWs through executions, starvation, forced labour and other mistreatment. The mistreatment of prisoners was common on the Eastern Front partly because the Soviet Union had not ratified the Geneva Convention on treatment of POWs, and Germany regarded itself as exempt from the convention on that front. Nevertheless, the Nuremberg Tribunal held that the Hague Conventions and other customary laws of war were binding on all belligerents.

About a third of Germans taken prisoner by the Soviet Union died in captivity. In comparison, The mortality rate of German and Japanese prisoners of the Western allies was 1 to 2 per cent. According to Soviet data, 594,000 Japanese soldiers of the Kwantung Army were interned after the Soviet invasion of Manchuria in August 1945. Of these, about 10% died in captivity by 1956. The Japanese government states that about 314,000 Japanese soldiers remain unaccounted for following the Soviet invasion of Manchuria, North Korea, Sakhalin and the Kuril Islands.

The Soviet Union made extensive use of forced labour of foreign civilians and POWs. POWs were interned in the Soviet forced labour camps of the Main Administration for Affairs of Prisoners of War and Internees, a camp system parallel to that of the Gulag, but distinct from it. Many died from malnutrition, the harsh climate and overwork.

Soviet soldiers committed mass rapes in occupied territories, especially Germany. Antony Beevor describes the Soviet rape of German women during the occupation of Germany as the "greatest phenomenon of mass rape in history", and has estimated that at least 1.4 million women were raped in East Prussia, Pomerania, and Silesia alone. He writes that Soviet women and girls liberated from slave labour in Germany were also violated. Soviet premier Joseph Stalin refused to punish the offenders.

The expulsion of 12 million to 14 million ethnic Germans from Soviet occupied territories is estimated to have caused between 500,000 and 2 million deaths from 1944 to 1946.

United Kingdom

Area bombing of cities

In June 1938, the British prime minister, Neville Chamberlain, stated that the bombing of civilians was contrary to international law. In the early years of the war, Britain's policy was to restrict aerial bombing to military targets. In February 1942, Britain adopted a policy of area bombing aimed at undermining the morale of enemy civilians, which the head of RAF Bomber Command, Arthur Harris, later stated was not contrary to international law. Although Britain's area bombing of German cities, including the bombing of Dresden (which killed at least 25,000 people), is sometimes considered a war crime, the legality of aerial bombing of civilian areas was unclear at the time.

Unrestricted naval warfare On 4 May 1940, in response to Germany's intensive unrestricted submarine warfare, the British Admiralty announced that all vessels in the Skagerrak were to be sunk on sight. This commenced Britain's unrestricted naval warfare campaign. Sociologist Nachman Ben-Yehuda argues this was contrary to the terms of the Second London Naval Treaty and other relevant international law at the time.

Alfred de Zayas writes that while it was British policy to rescue shipwreck survivors, German military documents provide credible evidence that the Royal Navy and Royal Air Force sometimes fired on survivors after the sinking of German vessels. In July 1941, the submarine commander Anthony Miers of HMS Torbay twice ordered his crew to kill enemy shipwreck survivors in the Mediterranean. Historian Jürgen Rohwer calls this "the only instance of a war crime committed by a British submarine commander." Miers was reprimanded but later was awarded the Victoria Cross and promoted to admiral.

Britain refused to recognise small hospital ships and often attacked them. They also refused to recognise hospital ships which they believed were used for military purposes in contravention of the Hague Convention. By May 1943, Britain had attacked nine German and 10 Italian hospital ships. On 12 September 1942, the Italian hospital ship Arno was sunk by RAF torpedo bombers off Tobruk. On 1 December, the British sank another Italian hospital ship, the Città di Tapani. The sinkings followed British intercepts of German coded messages showing that the ships were reportedly carrying military supplies, which was in contravention of the Hague Conventions.

On 18 November 1944, the German hospital ship Tübingen was sunk by two Beaufighter bombers off Pola, in the Adriatic Sea. Four crewmembers were killed and 16 wounded. A German military investigation concluded that the sinking was a war crime. A British investigation found that the ship was attacked in error. There was no official order to attack the ship and British policy was not to attack red cross vehicles and vessels.

Abuses against enemy military and POWs On the Western Front from June 1944 to May 1945, there were numerous cases of British troops killing enemy POWs, violating and looting the bodies of dead enemy troops, and forcing POWs to undertake military work in contravention of the Geneva Convention. Longden states that the killing of prisoners and enemy soldiers attempting to surrender was not on a large scale. However, it was more common when the British believed the enemy had previously killed British POWs or had fired on British troops after pretending to surrender, and when the British encountered SS troops and guards at liberated concentration camps.

Longden states that the desecration of corpses was uncommon on the Western Front, but did occur. In the Asia-pacific theatre, during the Burma campaign, there are cases of British soldiers removing gold teeth from dead Japanese troops and displaying Japanese skulls as trophies.

German POWs were sometimes forced to undertake tasks on the frontline such as digging trenches, carrying wounded soldiers, and digging graves for dead soldiers. There were also reports of German POWs being forced to clear minefields and fire on German positions. The British classified German military personnel captured after the German surrender as "Surrendered Enemy Personnel" rather than prisoners of war, thus avoiding the protections provided to them under the Geneva Convention.

The "London Cage", a MI19 prisoner of war facility in the UK during and immediately after the war, was subject to allegations of torture. The Bad Nenndorf interrogation centre in occupied Germany, managed by the Combined Services Detailed Interrogation Centre, was the subject of an official inquiry in 1947, which found that there was "mental and physical torture during the interrogations" and that "personal property of the prisoners were stolen".

Abuses against civilians On the Western Front in 1944–1945, British troops sometimes killed civilians or destroyed their homes if they had undisclosed weapons in them or showed support for the Nazis.