https://www.google.com/amp/s/www.nytimes.com/2018/05/03/us/p...
https://www.google.ca/search?q=uk+arms+sales+to+saudi+arabia...
"Discovered" because there were some reports of it, by one or two people, but I'm not sure how seriously they were taken.
I guess people concluded/knew some of this was happening, but the breakup of the camps was important for validation of the story.
(Edited given the responses)
> The mass of ordinary Germans did know about the evolving terror of Hitler's Holocaust, according to a new research study. They knew concentration camps were full of Jewish people who were stigmatised as sub-human and race-defilers. They knew that these, like other groups and minorities, were being killed out of hand. They knew that Adolf Hitler had repeatedly forecast the extermination of every Jew on German soil. They knew these details because they had read about them. They knew because the camps and the measures which led up to them had been prominently and proudly reported step by step in thousands of officially-inspired German media articles and posters according to the study, which is due to be published simultaneously in Britain and the US early next month and which was described as ground-breaking by Oxford University Press yesterday and already hailed by other historians.
> The reports, in newspapers and magazines all over the country were phases in a public process of "desensitisation" which worked all too well, culminating in the killing of 6m Jews, says Robert Gellately. His book, Backing Hitler, is based on the first systematic analysis by a historian of surviving German newspaper and magazine archives since 1933, the year Hitler became chancellor.
Either way, there was and still is great room to look the other way.
But regarding the situation in Germany and occupied areas during the war, you have to understand that by the time the death industry was in full swing, protesting openly in any way could have you yourself summarily executed or imprisoned - with unclear outcome.
In 1943 there was a hitch and the Nazis stepped back from mass murdering German women that dared to protest in their capital city.
The problem was that these good German women had Jewish husbands and weren't that keen on having their loved ones sent off for processing into lampshades:
https://en.wikipedia.org/wiki/Rosenstrasse_protest
* The actual facts of this protest are not clear and there is lots to be learned about not just what happened but the stories told about this event.
Cardinal von Galen openly preached from the pulpit about the destruction of "unworthy life" (the T4 program) in 1941.
Concentration camp inmates often weren't strictly confined to some walled-off camp, but had to go to work brigade actions all over the countryside, where they had limited contact to the populace, who quite often slipped them a bit of bread or so.
Even when no such work was happening around the populace, it was an open secret. You simply cannot keep a lid on it when tens of thousands of Germans saw something keeping watch over the inmates, delivering goods to the camps, requesting slave labor from the camps, actually building the ovens, conducting trains to the camps, or with soldiers returning from the eastern front.
https://www.reddit.com/r/AskHistorians/comments/6b1z61/did_t...