Auschwitz was the only death camp to cremate the bodies of murdered Jews on an industrial scale. Their bodies were burned not on pyres but in modern and efficient assemblies of crematorium furnaces. It is not entirely clear why the SS authorities decided to invest in the construction of such an extensive crematorium complex. No doubt, in part it resulted from an effective marketing campaign by the company producing the incineration furnaces, Topf und Söhne of Erfurt, the personal ambitions of the commandant Höss and his chief of the construction office Karl Bischoff as well as a combination of quite independent events, though all stemming from the need to increase in the efficiency of already existing Auschwitz crematorium. As the camp expanded in the years 1940–41 the number of corpses that every day needed to be burned also increased. Therefore the SS successively had to order new furnaces (three in all) for the crematorium in the Main Camp.

As the addition of three furnaces soon proved insufficient, in mid-1941 there emerged a plan to build a new crematorium with four furnaces, located between the concentration camp and the railway station. In October, however, this plan was rejected when engineer Kurt Prüfer of the Topf company put forward a project to build a very large crematorium with five three-retort furnaces. It was to stand next to the ‘old crematorium’, near the SS hospital and commandant’s head office.

Independently of these plans the SS construction office came to the conclusion that on account of the high mortality among Soviet prisoners of war at Auschwitz II-Birkenau (who were the first inmates of that camp), two additional crematorium furnaces would be required.

During a visit to Auschwitz on 27 February 1942 Bischoff’s superior SS-Oberführer Hans Kammler decided that instead of two new furnaces, Birkenau should have the crematorium with five three-retort furnaces originally planned for Auschwitz I.

The next phase in planning the constructing of another two new crematoria was associated with decisions made by Himmler in July 1942. Informed of the intention to intensify extermination in the makeshift gas chambers (‘cottages’) Engineer Prüfer proposed to build in their vicinity two more assemblies of crematorium furnaces. This idea was accepted, but soon afterwards the SS authorities came to the conclusion that even the addition of three large crematoria (later numbered II, IV and V) would not be sufficient. It was therefore decided that as well as the crematorium with five three-retort furnaces originally designed for the Main Camp (crematorium II) Birkenau should have another identical crematorium with the same number of furnaces and retorts (crematorium III).

The construction of all four crematoria was completed in the spring of 1943. At the time their incinerating capacity was estimated as follows:

For reasons that are not entirely clear a decision was made in mid-July 1943 for Crematorium I to be closed, the furnaces put out and the staff moved to Birkenau.