Sachsenhausen, one of the early concentration camps, was established in the summer of 1936. Located outside of Berlin, the main function of Sachsenhausen was to train officers to be commandants for the other camps.

Early in 1945 the Allies broke through to Berlin and started bombing on a nightly basis, creating large craters in the streets. The Nazis gathered about thousand Jews and transferred them from Auschwitz to Sachsenhausen, where a subcamp named Schwarzweide was established. This subcamp was responsible for filling in the bomb craters left by the Allied air assaults in Berlin. Of those thousand prisoners, less than a dozen survived the war. We can identify mail from the Schwarzheide subcamp by the initials SCHWH in the return address.