The average German was aware that:

• there were concentration camps in Germany which opponents of the regime and Jews were sent to, and later also homosexuals, prostitutes, vagrants, Jehova's witnesses, and convicted criminals. Hitler came to power in January 1933. On February 27 a Dutch communist and recent immigrant to Germany set fire to the Reichstag (parliament) building as a protest against the regime. The nazis seized upon this as a pretext to outlaw the communist party and arrest tens of thousands communists and other left-wing opponents as well as Jews. These were incarcerated in about 100 improvised camps. Later these would be consolidated under the auspices of the SS into a number of large, uniform camps that we are now familiar with, such as Dachau, Buchenwald, Bergen-Belsen, Sachsenhausen, etc.

• people were treated badly and died in the concentration camps. This was not a secret, though the usual reasons given to the next of kin and the outside world were disease (true enough), attempts to escape, and suicide.

• the dead were burned in crematoria. Most camps were located quite close to villages and towns, and the smell of burning corpses was unmistakable.

• from 1941 onwards German Jews and Jews in the occupied territories were being sent “to the East” to a fate not exactly known but certainly largely understood to be possibly death for many of them. Officially they were being “resettled in the East”. However, news of the rounding up of Polish Jews in ghettos from late 1939 on, were they died in large numbers, was widespread ,and many rumors and stories circulated about mass shootings of Soviet Jews by the Einsatzgruppen (special SS units) in the wake of the German invasion of the Soviet Union in June 1941. The deportation of German Jews proceeded entirely in the open, and was in fact heralded as a triumph of nazi policy to make Germany judenfrei (free of Jews) or judenrein (clean of Jews). Town after town was officially declared judenfrei when all of the Jewish inhabitants had been deported.

The average German was not aware that:

• the Jews were being gassed in death camps specifically designed for that purpose. It was a matter of extreme importance to the SS, which was in charge of the “final solution to the Jewish question”, that this should be kept a secret. Head of the SS Heinrich Himmler stated in a 1943 speech to the SS in Poznan: “I also want to mention a very difficult subject before you here, completely openly. It should be discussed amongst us, and yet, nevertheless, we will never speak about it in public. [...] I am talking about the "Jewish evacuation": the extermination of the Jewish people “ When the death camps of Treblinka, Sobibor and Belzec had served their purpose (the extermination of the Jews of Poland) they were carefully dismantled and all evidence of their purpose destroyed. When the Soviet Army was approaching first Majdanek and then Auschwitz the SS did its utmost to destroy as much evidence as possible in the limited time available: blowing up gas chambers, burning paperwork and moving most of the remaining prisoners into Germany.

This is what the German people meant when they said after the war “wir haben es nich gewusst” (we did not know). They did not know about the gas chambers. They did not know that there were purpose-built death camps that differed from the concentration camps they were familiar with. They did know everything I have listed above and they did know that deportation meant possible death, sooner or later.

All of the above applies to the average German only. Of course there were many who knew more: the SS, the German factories that supplied the early gas vans, the crematoria and the Zyklon-B, the people in charge of processing the gold teeth and human hair that was sent back from the death camps, the railway employees that ran the trains to the death camps, etc. etc.