The clash in perspectives between revisionist and anti-revisionists is especially evident on the gas van topic.
There was a gas van document, PS-501, which was presented early on at the IMT. This document if taken at face value does indeed seem to be incriminating. This is one of the few fairly explicit gassing documents that they can claim. Nothing like this was presented for the Auschwitz gas chambers.
Does this constitute good proof that there were gas vans? Anti-revisionists think it does. And they say we are being unreasonable in not only rejecting their eyewitnesses but now even documents. "You are just rejecting everything!" they cry.
I think these early comments from Paul Rassinier give some insight into this disagreement (this is from his Eichmann book).
I will say nothing of the celebrated "death buses" whose existence and utilisation are attested by Document P.S. 501 [99] (Volume XXVI, p. 1-2-10), which is an account by a sublieutenant from Marioupol with the date May 15th, 1942. The whole text will be found in the fourth part of this work, taken from David Rousset, who reproduced it in Le Pitre ne rit pas (The Clown does not laugh) (Paris, 1948).
These "buses", which the indictment refers to as "trucks", were supposedly equipped for asphyxiation by using the motor exhaust. 100,000 Jews are said to have been gassed in this way. Even at the rate of 50, or even 100 per "bus" or "truck", take your choice, one can see what a task it was. This idea, which poses the problem of whether there was time to asphyxiate 100,000 people in this way, or whether a considerable number of these "vehicles" - of which not one has been recovered - existed, in itself reveals the imbecility of the contention that this was part of a vast plan, perfected by the authorities of the Third Reich, to exterminate the Jews. If in truth vehicles of this kind did exist, they can only have been produced by private initiative and only the smallest number could have been produced. The cases reported are considered to have happened in the region of Chelmno, under the authority of one Globochnik. When one knows Globochnik (cp. 5th part), one can obviously not swear that he would not be an initiator of such a scheme. But extermination in numbers of 100,000 is manifestly just as false. If it were a few hundred, it would be possible to accept the figure; but 100,000, no, absolutely not.
Rassinier's remarks here are very early (the 1960s) and are by no means conclusive, but he is touching on important general points that are still relevant. I think what Rassinier is getting at here is the issue of
robustness of evidence. The evidence for something needs to be
commensurate with what is alleged. He does not dismiss the PS-501 document. He does not try to "explain" or "debunk" it. Rather he is simply wary of being asked to accept that 100,000 Jews were gas-vanned based largely on a piece of paper. Ok, we have piece of paper. However,
-No gas van has ever been found
-No designs for gas vans have ever been found (only a few documents referring to them)
-No photographs have ever been found
And on top of this, we have the issue of the scale of killing. As Rassinier notes, we aren't talking about 300 victims. They are claiming the victims ran into the six figures. At that grand scale, all sorts of questions and doubts arise. How were all these vans manufactured or converted? Who designed them? What sort of capacity did they have? Etc.
For me, one of the major problems (aside from the ones already mentioned) is the issue of the earliest gas van stories. This is similar to the problem with the stationary gas chambers where the earliest versions have steam chambers, electric floors, trap doors, and other silliness which strongly suggests the stories are not based in fact. With the gas vans, we also find a major variations in the stories.
This is the account given in the earliest Chelmno gassing story, the so-called Szlamek report (author also sometimes identified as Jakub Grojnowski or Shloyme Ber Winer). The report was recorded in the Warsaw ghetto. It is early because versions of it appeared in print in 1943. Here is one bit from it.
The truck was constructed in a special way and looked roughly like a regular grey van, hermetically sealed with two doors at the back. On the inside, the van was covered with sheet metal. There was no places to sit in the van. The floor was lined with wooden slats, like in a bathroom, and covered with a doormat. Between the interior of the van and the place where the driver was sitting were two little windows through which, using an electric lamp, he checked whether the victims were dead. Underneath the wooden slats were two 15-centimeters pipes coming from the driver's cabin. At the end, they had openings through which the gas could enter. The gas apparatus was located inside the driver's cabin, where only the driver sat.
This story says they used gas that was stored in some sort of gas apparatus, i.e.,
they used some other gas, not the engine exhaust. In 1943, the Soviets at the Krasnodar and Kharkov trials said the gas vans used diesel exhaust and that seems to be the version of the story that won out. By 1945, the story was engine exhaust. From what I have seen, the post-war testimonies all say they used exhaust (or they are too vague to tell). And for decades after the war, standard secondary sources likewise said the Chelmno vans used exhaust.
There are some mentions of bottled CO used in gas vans in the euthanasia program, but this is said to have happened much earlier. The 1985 version of Hilberg (Vol I, 333) says for example: "Vehicles equipped with bottled, chemically pure carbon monoxide had already been used in 1940 for gassing East Prussian mental patients in Soldau, a camp located in the former Polish corridor." But he makes no mention of this for Chelmno.
There is a newer book by academic Patrick Montague on Chelmno that was first published in 2011. This is the state-of-the-art from the mainstream. Prior to this Chelmno got only scant treatment in the general histories. From the promotional blurb for it:
As the first extermination camp established by the Nazi regime and the prototype of the single-purpose death camps of Treblinka, Sobibor and Belzec, the Chelmno death camp stands as a crucial but largely unexplored element of the Holocaust. This book is the first comprehensive work in any language to detail all aspects of the camp's history, organisation and operations and to remedy the dearth of information in the Holocaust literature about Chelmno, which served as a template for the Nazis' 'Final Solution'.
What is curious about the Montague book (and I should say I checked this one thing but I have not read the whole thing yet) is that he seems to have noticed the problem with the Szlamek report and he does make some attempt to square the circle. Montague's theory is as follows (pg. 204): "The original gas van was not the only van used in the camp. RSHA sent two of its smaller vans to Chelmno in early January at the latest, presumably the Opel-Blitz vans. " That is, he thinks there was one van that used bottled CO or something (which would be more consistent with the Szlamek report) but that two exhaust-based gas vans arrived around January 1942 and this earlier design was then seemingly forgotten.
I don't buy it. I would need to re-read but as I recall Szlamek describes two vans and he describes them as being the same. He knows nothing about an exhaust-based gas van. And there's no indication at all of the vans having utterly different gassing mechanisms. My working hypothesis right now (open to revision) is that the exhaust-based gas vans were popularized by the Soviets around 1943 and this story was applied to Chelmno around 1945. And only recently was there an attempt to harmonize this with the earliest version of the story.