Mitläufer is the German Nazi equivalent of the term "fellow traveller" for communism. A person who has not commited any war crimes but whose association with the German Nazi state is such that does not allow him to be exonerated from such crimes.
I was wondering if there is a term of even a discourse in among historians in European occupied states, on people who may have not themselves have persecuted Jews but their association with the Holocaust is direct, usually by exploitation. These are not run-of-the-mill collaborators and in some cases they can even work with the local Resistance. But they can passively or actively accept the benefits of the deportations, eg a local University exploiting the jewish cemetery in order to expand or churches asking and getting Jewish assets. Or a high state official accepting the deportations of Jews but not of Christians. Or policemen who participate on Vel 'Hiv roundup but on the other hand are part of the maquis.
One cannot call them "collaborators" because they do not necessarily collaborate with the Germans; as I said in some cases they can even work with the Resistance or be victimized themselves. They are also not passerbys. On the other hand one gets the impression that should it have concerned "real" compatriots and not Jewish compatriots, there would be no hesitation in a more heavy handed approach. Can someone offer a glimpse into the discourse on their field or country or even offer how we could describe the phenomenon because I even lack the term of it.
In the case of France, there is no current term for this type of collaboration, because it was included in the postwar épuration ("purge") process from the start. While your question focuses on war crimes and on the Holocaust, people tried for collaboration with the Nazis were accused of wide range activities, which can be roughly divided in three types: political (people in the Vichy administration and those who supported Vichy ideology or Nazism), economic (people who did business with the Germans and/or benefited from the war), and professional (people whose work benefited the German war effort).
The épuration was a long and drawn-out process. The trials went on until the 1950s and the last collaborators were executed in 1954. All in all, the épuration concerned about 500,000 French people: about 100,000 were sentenced by the courts, 25,000 civil servants were sanctioned and about 10,000 people were executed, summarily or legally.
Starting in August 1944, the épuration was at first a chaotic and bloody extrajudicial process - or half-judicial, as it was in some cases condoned by the authorities -, conducted by local "courts" (or mobs) who punished and sometimes executed people denounced by their community. This early épuration could result from personal revenge, or it could be a continuation of war when the fighting was still going on. The accused could be people known to have worked directly for Vichy or the Germans, shopkeepers who had participated in the black market, women who had (allegedly) slept with German soldiers, and more generally all those found to have been too comfortable with the occupiers, like fashion designer Gabrielle "Coco" Chanel (who fled to Switzerland). This was followed by a more legal process where official courts tried collaborators from all walks of life and all levels of involvement - war profiteers, members of the Milice, intellectuals, industrialists, administrators, politicians, etc.
The most prominent of the accused were hardcore collaborationists who had ordered or committed themselves tortures and massacres, or committed treason by choosing Germany over France, and they were sentenced to prison or executed. However, most of the accused were people that would fit your concept of "fellow travellers": they did not commit war crimes or acts of treason, but they had been supporting willingly, actively, and visibly the Vichy regime and/or the German occupiers, or were guilty of economic or professional collaboration. The bulk of the people who stood trial were low-level collaborators, and sometimes their involvement in collaboration was minimal or even dubious, only relying on hearsay.
The épuration process, even when carried out legally, was hardly an efficient and consistent one, as situations were often greyish and compromises had to be made. Well-known collaboration cheerleaders like journalists were easier to target and more expendable than anonymous, efficient Vichy administrators who held technical positions and whose guilt was difficult to establish. Many of the accused were able to prove that they had helped the Resistance and got away. This was the case of René Bousquet, the secretary general to the police between 1942 and 1943, and the main French organizer of the roundups of the Vel' d'Hiv and Marseille and of the later deportation of Jews to extermination camps. In 1949, Bousquet got a slap on the wrist, kept a low profile for a while, and resumed his career in the private sector after a few years, all his sins forgotten, and it is only in the late 1980s that his case resurfaced. Another example is that of prefect Maurice Papon, another Vichy official involved in the Holocaust, who completely bypassed the épuration thanks to his alleged Resistance activities and continued his career as a civil servant and later as a conservative politician.
The examples of Bousquet and Papon demonstrate the messiness of the épuration process, as well as the relatively little weight given in postwar France to what we consider today to be a central issue: the complicity of Vichy France in the extermination of European Jews. In her recent study of the purge and of the related court proceedings, Bénedicte Vergez-Chaignon notes that "there is an exorbitant discrepancy between the grievances leveled at the accused and contemporary questions". Indeed, while the existence of the death camps was known, the specifics of the extermination process and of the role of French authorities were not yet well established. Documenting the Holocaust was in its very early stages. Antisemitism was not mentioned in the French penal code: it was just an opinion. The crimes linked to the Shoah did not fit easily in the categories used to accuse people of collaboration: treason, helping the enemy, and undermining national defence. Judges had to find contorted ways to punish collaborators for this type of crimes: for instance, a Vichy administrator who had created a police unit to hunt Jews was condemned for having "served German racist policies in France", so he was sentenced for treason, not for rounding up Jews. Other civil servants who had participated in the identification and capture of Jews saw their charges dropped because it was understood that they had done nothing more than following (German) orders and had not engaged in "antinational" activities. Gendarmes who had been guards in the Drancy camp (from where Jews were sent to the death camps) were accused of brutality and theft against Jewish internees, not of participating in the round up and later deportation of the prisoners (again, the rationale is that they were following orders), and in any case they got away with relatively light sentences.
More generally, the capture and deportation of Jews was not seen as a specific crime, just one of the many that the épuration courts had to deal with, and not one that non-Jewish French people at the time would have considered as a priority. There was also the additional problem that many victims had never returned from the camps, which made accusations of murder difficult to sustain due to the lack of proof. Some Jewish survivors were wary of "stealing" the spotlight from other victimized groups lest it would rekindle antisemitism. How to break the French "blockade of silence" regarding the extermination of Jews was debated by the members of the Center of Contemporary Jewish Documentation, created in Paris in 1944. But it was only in the 1970-80s - notably thanks to American historian Robert O. Paxton - that the role of Vichy in the Holocaust became a major point in the narrative of wartime collaboration. The existence of several still living Vichy officials who had been involved in the rounding up and deportation of Jews was revealed to the public: while Louis Darquier de Pellepoix had been living in exile in Spain since 1947 (he had been sentenced to death for his Vichy activities), both René Bousquet and Maurice Papon had had prominent postwar careers. This came as a shock.
So, half a million people were tried for collaboration activities that ranged from benign ones to crimes against humanity. Many of them were punished, but a few, or perhaps many, evaded justice because the crimes they had committed - notably their willing participation to the Holocaust - were not yet recognized as such in the postwar, and it took another three decades for justice and public opinion to acknowledge this.
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