It was formed in 1925 from a merger of six chemical companies: Agfa, BASF, Bayer, Chemische Fabrik Griesheim-Elektron [de], Hoechst, and Weiler-ter-Meer.

Otto Bayer discovered the polyaddition for the synthesis of polyurethane in 1937,[5] and three company scientists became Nobel laureates: Carl Bosch and Friedrich Bergius in 1931 "for their contributions to the invention and development of chemical high pressure methods",[6] and Gerhard Domagk in 1939 "for the discovery of the antibacterial effects of prontosil".

[b] These companies continued to operate as an informal cartel[citation needed] and played a major role in the West German Wirtschaftswunder.

In 2004, the University of Frankfurt, housed in the former IG Farben head office, set up a permanent exhibition on campus, the Norbert Wollheim memorial, for the slave labourers and those killed by Zyklon B.

[20] The three major firms had also integrated upstream into the production of essential raw materials, and they began to expand into other areas of chemistry such as pharmaceuticals, photographic film, agricultural chemicals and electrochemicals.

Contrary to other industries, the founders and their families had little influence on the top-level decision-making of the leading German chemical firms, which was in the hands of professional salaried managers.

[21] Because of this unique situation, the economic historian Alfred Chandler called the German dye companies "the world's first truly managerial industrial enterprises".

During a trip to the United States in the spring of 1903, he had visited several of the large American trusts such as Standard Oil, U.S. Steel, International Paper and Alcoa.

[25] In 1904, after returning to Germany, he proposed a nationwide merger of the producers of dye and pharmaceuticals in a memorandum to Gustav von Brüning, the senior manager at Hoechst.

As Hoechst, Cassella and Kalle were connected by mutual equity shares and were located close to each other in the Frankfurt area, this allowed them to cooperate more successfully than the Dreibund, although they also did not rationalize or consolidate their production facilities.

In France Établissements Poulenc Frères and Société Chimique des Usines du Rhône merged to form Rhône-Poulenc in 1928.

[32] IG Farben was controversial on both the far left and far right, partly for the same reasons, related to the size and international nature of the conglomerate and the Jewish background of several of its key leaders and major shareholders [citation needed].

[34] By 1938 the Jews on the board had resigned and the remaining Jewish employees had been dismissed after Hermann Göring issued a decree, as part of the Nazis' Four Year Plan (announced in 1936), that the German government would make foreign exchange available to German firms to fund construction or purchases overseas only if certain conditions were met, which included making sure the company employed no Jews.

Carl Bosch and Friedrich Bergius were awarded the Nobel Prize in Chemistry in 1931 "in recognition of their contributions to the invention and development of chemical high pressure methods".

The IG Farben plant's workforce consisted of slave labour from Auschwitz, leased to the company by the SS for a low daily rate.

's immense productive facilities, its far-reaching research, varied technical expertise and overall concentration of economic power, Germany would not have been in a position to start its aggressive war in September 1939.

The minutes of a meeting of the Commercial Committee on 10 September 1937 noted: It is generally agreed that under no circumstances should anybody be assigned to our agencies abroad who is not a member of the German Labor Front and whose positive attitude towards the new era has not been established beyond any doubt.

[42]This message was repeated by Wilhelm Rudolf Mann, who chaired a meeting of the Bayer division board of directors on 16 February 1938, and who in an earlier meeting had referred to the "miracle of the birth of the German nation": "The chairman points out our incontestable being in line with the National Socialist attitude in the association of the entire 'Bayer' pharmaceutica and insecticides; beyond that, he requests the heads of the offices abroad to regard it as their self-evident duty to collaborate in a fine and understanding manner with the functionaries of the Party, with the DAF (German Workers' Front), et cetera.

"[43] By 1943, IG Farben was manufacturing products worth three billion marks in 334 facilities in occupied Europe; almost half its workforce of 330,000 men and women consisted of slave labour or conscripts, including 30,000 Auschwitz prisoners.

[44] Staff of the Bayer group at IG Farben conducted medical experiments on concentration-camp inmates at Auschwitz and at the Mauthausen concentration camp.

The patients were suffering from, and in many cases had been deliberately infected with, typhoid, tuberculosis, diphtheria and other diseases, then were given preparations named Rutenol, Periston, B-1012, B-1034, B-1036, 3582 and P-111.

"[47] Between 1942 and 1945, a cyanide-based pesticide, Zyklon B, was used to kill over one million people, mostly Jews, in gas chambers in Europe, including in the Auschwitz II and Majdanek extermination camps in German-occupied Poland.

[48] The poison gas was supplied by an IG Farben subsidiary, Degesch (Deutsche Gesellschaft für Schädlingsbekämpfung MbH, or German Company for Pest Control).

Peter Hayes writes that the board did not meet after 1940, and that although Mann "continued to review the monthly sales figures for Degesch, he could not necessarily have inferred from them the uses to which the Auschwitz camp was putting the product".

Ernst Struss, secretary of the IG Farben's managing board, testified after the war that the company's chief engineer at Auschwitz had told him about the gassings.

[57] Hayes writes that the inmates of Auschwitz III, which supplied the slave labour for IG Farben, were well aware of the gas chambers, in part because of the stench from the Auschwitz II crematoria, and in part because IG Farben supervisors in the camp spoke about the gassings, including using the threat of them to make the inmates work harder.

The judges ruled that the prosecution had not shown that the defendants or executive board "had any persuasive influence on the management policies of Degesch or any significant knowledge as to the uses to which its production was being put".

[60] Wurster became chair of the IG Farben board, helped to reestablish BASF as a separate company, and became an honorary professor at the University of Heidelberg.

[70] Ambros, Bütefisch, Dürrfeld, Krauch and ter Meer were convicted of "participating in ... enslavement and deportation for slave labor".

While it did not join a national compensation fund set up in 2001 to pay the victims, it contributed 500,000 DM (£160,000 stg or €255,646) towards a foundation for former captive labourers under the Nazi regime.