Bruno Emil Tesch (14 August 1890 – 16 May 1946) was a German chemist, entrepreneur, and war criminal. Together with Gerhard Peters and Walter Heerdt, he invented the insecticide Zyklon B. He was the owner of Tesch & Stabenow (called Testa), a pest control company he co-founded in 1924 with Paul Stabenow in Hamburg, Germany. During the Holocaust, Tesch sold vast quantities of Zyklon B, utilising his pesticide as a way to commit genocide. Over 1.1 million people (mainly Jews) were murdered by the Nazis using Zyklon B. A former employee of Tesch later said he was motivated not by ideology, but financial gain.
Following the end of World War II, he was arrested by British occupation authorities, tried as a war criminal, and executed. Tesch and his deputy executive, Karl Weinbacher, were the only businessmen to be executed for their role in Nazi war crimes in Western Europe.
After passing his high school exams in 1910, Tesch studied mathematics and physics for a semester in 1910 at the University of Göttingen before studying chemistry at the University of Berlin. He received his doctorate in 1914 and volunteered for military service at the start of the First World War. After a war injury, Tesch was appointed by Fritz Haber to the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry to develop "chemical weapons of war". After the war, he stayed there as Haber's personal assistant until March 1920. Tesch then took over the management of the Berlin branch of the German Society for Pest Control (Degesch) GmbH. Tesch joined the Nazi Party on 1 May 1933, albeit not as an active member. He became a supporting member of the SS the same year. When Emil Sehm, a former employee of Tesch who became an important witness at his trial, was asked to give his opinion about him, he said Tesch was not motivated by ideology."Dr. Tesch was solely a business man and, according to my opinion, he was a very unscrupulous business man, a business man who would be prepared to walk over dead bodies; that is my opinion."
Tesch, along with fellow chemists Gerhard Peters and Walter Heerdt, with the support of I.G. Farben, began research into the use of hydrogen cyanide as a fumigating agent. They developed a process in which the hydrogen cyanide could be manufactured and used in a solid form.
The patent was assigned to Degesch, "Deutsche Gesellschaft für Schädlingsbekämpfung mbH" (German Limited Company for Pest Control), a subsidiary of I.G. Farben, with Walter Heerdt being the only one of the inventors to receive patent rights, a portion of the proceeds from the manufacture and sale. Peters joined Degesch and became managing director during World War II. Degesch was designated by the German government to set the safety rules and standards for the use of Zyklon B, and was given the authority to authorise shipments from the manufacturer to the customer after the strict criteria were met.
Tesch & Stabenow manufactured neither Zyklon B nor any other chemicals. It was primarily a pest control company specialising in fumigation of commercial properties such as the warehouses and freighters in the Port of Hamburg. Zyklon B was produced by Dessauer Werke and Kaliwerke.
In 1925, Tesch & Stabenow—partly due to the largesse of Paul Haber of Degesch—received the exclusive rights to distribute the insecticide Zyklon B east of the Elbe River. In 1927, Stabenow departed from the firm. Tesch held a 45% share of the company, and Degesch held 55%. Tesch assumed sole ownership of the company in 1942.
During World War II, Tesch & Stabenow sold massive quantities of Zyklon B to the SS. The gas was sent to Auschwitz, Sachsenhausen, Neuengamme, Gross-Rosen, Majdanek, and Ravensbrück concentration camps. In these camps, the SS used the Zyklon B they had purchased to murder approximately 1.1 million people.
An investigation into Tesch started after a former Testa bookkeeper, Emil Sehm, wrote to British military authorities, who were present in Hamburg since the city was in the British military government's zone of Allied-occupied Germany. Sehm said that in 1942, he had come across one of Tesch's travel reports. In it, Tesch had recorded an interview with leading members of the Wehrmacht, during which he was told that the burial, after shooting, of Jews in increasing numbers was proving increasingly unhygienic, and that it was proposed to kill them with prussic acid. Allegedly, when Tesch was asked for his views, he had proposed to use the same method, involving the release of prussic acid gas in an enclosed space, as was to exterminate vermin. He had then trained the SS to use Zyklon B to kill human beings.
Sehm said he copied this report and showed it to a close friend, Wilhelm Pook. Pook advised Sehm to destroy the letter immediately since keeping the letter posed a safety risk. Sehm destroyed the letter. He was fired for unknown reasons after the firm's building suffered an air raid in July 1943.
Tesch was detained in September 1945. British officers Walter Freud and Fred Pelican were assigned to the case. The day after Tesch's arrest, Sehm accompanied the British to the firm building, only to find that registry had seemingly been destroyed in an air raid (it was later suspected that the registry had been intentionally destroyed).
During questioning, Tesch presented himself as a respectable businessman and chemist. He denied all suggestions and accusations that he had collaborated with the SS regarding the extermination of Jews. He said he never attended a conference discussing the subject, had not devised any methods for using Zyklon B other than fumigating the barracks, and had not known that the gas was being used to kill people. Tesch said he did not even know the gas was being sent to concentration camps.
Tesch admitted to being a member of the Nazi Party and a "supporting member of the SS". He explained that he had been affiliated with the SS Hygiene Institute to obtain their business. Freud did not believe Tesch, but had no evidence beyond Sehm's word. At the same time, Freud was facing pressure from high command to release Tesch, since British occupation forces were using Zyklon B to fumigate their ships. Against the wishes of Freud and Pelican, Tesch was released on 1 October 1945.
Both men immediately started lobbying their superiors to let them continue their investigation. Freud, who was a chemist himself, was adamant that the investigation be allowed to continue. He and Pelican told high command that Tesch's case was the first time they were dealing "not with people directly concerned in the murder or ill-treatment of prisoners or slave workers, but with those who lent their skill and services to facilitating the gruesome work of the concentration camps and so identified themselves with breaches of the laws of war on a wholesale scale." Their superiors relented, and Tesch was re-arrested on 6 October 1945. Freud and Pelican started searching through other files, and found that the firm had a sharp rise in profits in 1942 and 1943, when the mass gassings were at their peak. However, they could not find anything suggesting that Tesch or his employees knew their product was being used to kill people. Raids of the firm's employees turned up nothing.
During further questioning, Freud reported that Tesch adopted an attitude of ignorance carried "to an absurdity." The questioning of Tesch's deputy executive, Karl Weinbacher, also failed to get any answers. Freud reported that Weinbacher was "blindly obedient, has a slow brain", and was "an arrogant man with limited intellect." Freud said Weinbacher "was so insolent that special steps had to be taken by the interrogating officer."
The British administration was soon insisting that the firm needed to resume its fumigating. The firm's accountant, Alfred Zaun, was asked to substitute for Tesch. He agreed, but said he needed written authorisation from Tesch. Freud and Pelican, becoming desperate, organised a meeting with hidden microphones, hoping that Tesch might incriminate himself. However, he and Zaun whispered to each other quietly enough that the microphones did not pick up anything.