In 1929, Viktor Brack became a member of the NSDAP and the SS. In 1936, he was supervising operation of the office 2 (Amt 2) in the Chancellery of the Führer in Berlin, that office examined complaints received by the Führer from all parts of Germany. In November, 1940 Brack was promoted to the grade of Oberführer.

During the Doctors' Trial Brack testified from the witness stand that after 1941, when the extermination of Jewish population by Nazis was at full capacity, Himmler ordered him to contact physicians involved previously in Euthanasia Program, to find out the way of sterilizing strong and young Jews who were able to worked for the German war economy. The idea was to find out the method which could be conducted without victim’s knowledge.

In March of 1941, Brack fulfilled his assignment and prepared a report for Himmler, in which, he described the method of sterilizing patients using X-rays on the mass scale and without victims being aware of the consequences.

On 23 June, 1942 Brack wrote the following letter to Himmler:

Dear Reichsführer, among 10 millions of Jews in Europe, there are, I figure, at least 2-3 millions of men and women who are fit enough to work. Considering the extraordinary difficulties the labor problem presents us with, I hold the view that those 2-3 millions should be specially selected and preserved. This can however only be done if at the same time they are rendered incapable to propagate. About a year ago I reported to you that agents of mine have completed the experiments necessary for this purpose. I would like to recall these facts once more. Sterilization, as normally performed on persons with hereditary diseases is here out of the question, because it takes too long and is too expensive. Castration by X-ray however is not only relatively cheap, but can also be performed on many thousands in the shortest time. I think that at this time it is already irrelevant whether the people in question become aware of having been castrated after some weeks or months, once they feel the effects. Should you, Reichsfüuehrer, decide to choose this way in the interest of the preservation of labor, then Reichsleiter Bouhler would be prepared to place all physicians and other personnel needed for this work at your disposal. Likewise he requested me to inform you that then I would have to order the apparatus so urgently needed with the greatest speed. Heil Hitler! Yours VIKTOR BRACK.

Following the letter, Himmler ordered to arrange experiments to be conducted on prisoners in one of concentration camps. Since Brack was transferred to an SS division, his deputy Blankenburg would undertake the task and "immediately take the necessary measures and get in touch with the chiefs of the main offices of the concentration camps."

From the testimony given by a French physician of Jew descent who was a prisoner in Auschwitz from September 1943 to January 1945, can be found that it was in Birkenau camp (adjacent to Auschwitz) where people were sterilized by SS doctors. About 100 male Poles who had been sterilized at Birkenau, were attended by the witness after the operation. Later according to the witness, members of the group were castrated by the camp physicians.

There were other evidences from which it is clear that sterilization using X-rays was conducted on other groups of persons who were subjected by the method to an excruciating pain and later castrated.

Also, in the Doctors' Trial at Nurenberg, Brack was implicated in executing Euthanasia Program which later merged as famous "Action 14 f 13"; the extermination of concentration camp inmates by methods used in euthanasia.

The rationale behind the "Action 14 f 13" was to get rid of “useless eaters” and conserve medical and food resources for German Arm Forces. In consequence not only German citizens by also other nationals from other countries were put to death by such monstrous and inhuman program.