On 20 November 1945, in a courtroom in the bombed-out German city of Nuremberg, twenty-one of the most powerful surviving leaders of Nazi Germany sat in the dock to face trial before judges from four nations. It was the first time leaders of a state had been tried before an international court for waging aggressive war and for mass atrocities against civilians. To understand why it happened, and why it was controversial, we start with the decision to hold a trial at all.

The crimes

The Second World War in Europe, from 1939 to 1945, killed tens of millions of people. Nazi Germany invaded Poland, then much of Europe, and in 1941 the Soviet Union. Behind its armies came a policy of conquest, enslavement and extermination. In the Holocaust, Nazi Germany and its collaborators murdered about six million Jews, around two thirds of the Jews of Europe, in mass shootings, ghettos and death camps such as Auschwitz and Treblinka. Millions of others were murdered too: Roma, Soviet prisoners of war, Polish and other civilians, people with disabilities, political opponents and others the regime targeted.

As Allied armies liberated the camps in 1944 and 1945, soldiers and journalists saw the evidence with their own eyes: piles of bodies, starving survivors, gas chambers and crematoria. The question of what to do with those responsible became unavoidable.

Early warnings

The Allies had promised punishment during the war. In January 1942, representatives of governments in exile from occupied countries met in London and declared that punishing war crimes was one of their principal war aims. In the Moscow Declaration of October 1943, the United States, Britain and the Soviet Union announced that Germans responsible for atrocities would be sent back to the countries where they had committed their crimes to be judged there, while the major criminals, whose crimes had no particular geographical location, would be punished by joint decision of the Allies. How that joint decision would be made was left open.

Shoot them?

Many leaders initially favored a quick solution. The British prime minister Winston Churchill and some of his ministers proposed that the top Nazi leaders be declared outlaws and shot once identified, without trial. They feared that a trial would be long, give the Nazis a platform and risk acquittals on technicalities. According to Churchill's later account, at the Tehran Conference in 1943 Soviet leader Joseph Stalin proposed, half in jest or perhaps not, that fifty thousand German officers be shot, and Churchill walked out of the room in protest.

In the United States, Treasury Secretary Henry Morgenthau also supported summary execution of leading Nazis. But Secretary of War Henry Stimson argued strongly for a trial. He believed that punishing the defeated without proof would look like vengeance and would teach the wrong lesson. A trial, he argued, would establish the facts beyond dispute and show that the Allies held themselves to standards of law and fairness that the Nazis had abandoned.

The decision

Stimson's view won out. After President Franklin Roosevelt's death in April 1945, President Harry Truman supported a trial, and the Soviet Union, which had its own tradition of show trials, agreed. Britain came around. In June 1945, representatives of the four main Allied powers, the United States, Britain, the Soviet Union and France, met in London to design a court.

Three reasons for a trial

Supporters of a trial gave several reasons that remain central to debates about justice after atrocity.

• Truth. A trial would create a permanent, public record based on evidence, making it harder for anyone to deny what had happened.
• Individual responsibility. It would hold specific individuals accountable rather than blaming a whole nation.
• The rule of law. It would show that even the worst crimes would be met with law rather than revenge.

Worked example: three choices after atrocity

Imagine you are an Allied leader in 1945 with the surviving Nazi leaders in custody. Weigh three options.

• Summary execution. Quick and certain. It prevents the defendants from using a courtroom as a stage. But it establishes no public record, invites the charge of vengeance, and lowers the victors to the methods of the defeated.
• Amnesty and forgetting. Some argue that a defeated nation must be allowed to rebuild without endless prosecution. But after crimes of this scale, forgetting would insult the victims and teach future leaders that atrocity can go unpunished.
• A trial. Slow, expensive and risky; some defendants might be acquitted. But it can establish facts, separate the guilty from the innocent and affirm that every person, even the worst criminal, is judged by law.

The choice of a trial reflected a conviction that later became central to human rights: even those accused of the worst crimes are entitled to a fair hearing, because justice that denies the dignity of the accused is not justice. That conviction would be tested at every stage of what followed.