In 1942, after witnessing mass murders in the Belzec and Treblinka Nazi extermination camps, Gerstein gave a detailed report to Swedish diplomat Göran von Otter, as well as to Swiss diplomats, members of the Roman Catholic Church with contacts to Pope Pius XII, and to the Dutch government-in-exile, in an effort to inform the international community about the Holocaust as it was happening.

Kurt Gerstein was born in Münster, Westphalia, on 11 August 1905, the sixth of seven children in a Prussian middle-class family that was described as strongly chauvinistic and "totally compliant to authority".

[1] His father, Ludwig, a former Prussian officer, was a judge and an authoritarian figure who proudly proclaimed that in his family's genealogical tree there was only Aryan blood and exhorted generations to "preserve the purity of the race!

[10] Like many others of his generation, Gerstein and his family were deeply affected by what they saw as the humiliation of Germany by the terms of the Treaty of Versailles and so were attracted by the extreme nationalism of the Nazi Party.

[12] On 4 September 1936, Gerstein was arrested for distributing anti-Nazi material, held in protective custody for five weeks and ultimately expelled from the Nazi Party.

One document indicates that it was the result of his outrage over the death of a sister-in-law, who apparently was murdered under the "euthanasia" program Action T4, directed at the mentally ill.[13][14] Other documents suggest he had already made his decision before she was murdered and that her death reinforced his desire to join the SS to "see things from the inside", try to change the direction of its policies and publicize the crimes that were being committed.

He supplied hydrogen cyanide (Zyklon B) to Rudolf Höss in Auschwitz from the Degesch company (Deutsche Gesellschaft für Schädlingsbekämpfung Vermin-Combating Corporation") and conducted the negotiations with the owners.

[18] On 17 August 1942, together with Rolf Günther and Wilhelm Pfannenstiel, Gerstein witnessed at Belzec the gassing of some 3,000 Jews who had arrived by train from Lwow.

[20] Von Otter talked with high-ranking officials at the Swedish Foreign Ministry, but Gerstein's revelations were never passed on to the Allies or to any other government.

[citation needed] In the meantime, Gerstein tried to make contact with representatives of the Vatican, the press attaché at the Swiss legation in Berlin and a number of people linked to the Confessing Church.

After his surrender in April 1945, Gerstein was ordered to report about his experiences with gassing and the extermination camps in French, followed by two German versions in May 1945.

[22] On 22 April 1945, two weeks before Nazi Germany's surrender, Gerstein voluntarily gave himself up to the French commandant of the occupied town of Reutlingen.

His search for Christian values and ultimate decision to betray the SS by attempting to expose the Holocaust and informing the Catholic Church is portrayed in the narrative film Amen., released in 2002, starring Ulrich Tukur as Gerstein and directed by Costa-Gavras.

[25] William T. Vollmann's Europe Central, the National Book Award fiction winner for 2005, has a 55-page segment, Clean Hands, which relates Gerstein's story.