There are few “flat earthers” these days and the majority of people no longer believe that the moon is made of green cheese. By contrast, denying the Holocaust, that is, claiming that the genocide of the Jews by Nazi Germany and its allies during World War II ever took place, seems to be flourishing.

It is an extreme example of an increasingly common phenomenon: rejecting facts when they happen to be inconvenient. At least when, in the middle ages, people thought that the sun orbited the earth, they had no proof to the contrary. Holocaust denial is a position consciously held not because there is no evidence but despite it. Like antisemitism, to which it is closely related, Holocaust denial is not based on evidence but is a position held because its adherents want it to be true. Unfortunately, it is not.

Just as antisemitism is a claim about Jews that rests ultimately on mythical thinking – Jews as puppet-masters behind world events, for example – so Holocaust denial rests on similar conspiracy theories – that the Jews concocted the whole story to extract money from Germany and to promote Zionism, for example.

People with strongly-held antisemitic beliefs are rarely amenable to having their views changed by the presentation of evidence, and the same is true of Holocaust denial. What follows is not aimed at those who are unshakeable in their belief that the Holocaust never happened, although it would be nice to think that their minds could be changed (they probably do not read the JC, in any case). Rather, I want to show that, when people – often youngsters – are confused by the easily-accessible lies that proliferate on the internet, it is not hard to put them straight.

Camps across Europe

Germany and Nazi-occupied Europe during World War II were covered in camps. Everyone has heard of Auschwitz, and Holocaust denial often presents itself as the “Auschwitz lie”. But, according to recent research, there were thousands of camps all over Nazi Europe. By the end of 1944, there were a dozen main camps to which were attached about 1,100 sub-camps. This figure does not even include camps run by firms, by local councils and bodies other than the SS.

These did not only hold Jews: three million Soviet POWs were killed in Nazi camps, mostly by being starved to death, and tens of thousands of Gentile Poles, Soviets, Yugoslavs, French and others from across Europe were held as political prisoners in camps such as Buchenwald and Gross-Rosen. But Jews were targeted for murder, and the fact that there were Jewish survivors was only a result of the fact that the Third Reich, desperate for labour as the war turned against it, made use of Jewish camp inmates in larger numbers in autumn 1944.

At the start of the Holocaust, Jews were not killed in camps but were murdered – about 1.5 million of them – in pits on the edges of their villages and towns in eastern Europe. The work of Father Patrick Desbois and his Yahad-In Unum organisation in locating these gravesites is bringing ever greater certainty to where these people died.

A lot of evidence, in almost every European language

I mention the Nazi camp system and the work of locating victims of the Einsatzgruppen to provide a sense of the continent-wide nature of the crime we now call the Holocaust. The point is simply that, from Amsterdam to Thessaloniki, from Klaipeda to Lyon, one can see basically the same thing happening. That is a lot of evidence to produce, in almost every European language. They are of course Holocaust institutions and, from a neo-Nazi perspective, invested in the very thing that is being denied, but a glance at the online photography and document collections of Yad Vashem, the US Holocaust Memorial Museum, or the Wiener Library in London indicates that a fabrication on this scale is simply not possible.

Evidence is clear via the International Tracing Service

There is no greater proof of this abundant evidence than the International Tracing Service. Based in Bad Arolsen in northern Hesse, Germany, the ITS was created after the war by the Allies in order to trace missing people. Run by the International Committee of the Red Cross after 1955, since 2007 it has been open to researchers and the general public.

It holds over 30 million documents, spanning 26 kilometres of shelving, and is the world’s largest archive of material relating to Nazi Germany and the Holocaust. There are better things to do with this material than confront Holocaust denial but, if one is not already satisfied with the abundant scholarly literature or the remaining material evidence across Europe, then there is no shortage of documentation here, far more than could have been consciously produced as a fraud.

In December 1942, for example, an SS man, Untersturmführer Kinna, wrote a report on the transport of 644 Poles to Auschwitz that had taken place a few days earlier. He began by noting: “that only those capable of work should be delivered, so as to avoid burdening the camp as well as the transport traffic as much as possible.” Then he went on, very openly:

"The simple, idiots, cripples and sick people must be removed from the camp in the shortest possible time by liquidation. This measure encounters an obstacle insofar as in contrast to the measures ordered for Jews by the RSHA, Poles have to die a natural death. The camp leadership would thus prefer to avoid an allocation of those unable to work."

His complaint was about non-Jewish Poles but he also quite casually referred to the fact that Jews were not dying a “natural death.” The ITS is full of such information and it is only one, albeit the largest, of many archival sources. Almost every local and national archive across Europe contains material relating to the Holocaust. Choosing to believe that this was all created by a vast conspiracy and that the Holocaust never happened is the neo-Nazi equivalent of a green cheese moon.

Dan Stone is Professor of Modern History and Director of the Holocaust Research Institute, Royal Holloway, University of London