I am currently reading the new history of the Holocaust by British historian Laurence Rees and it reminded me of a comment in the Awake! magazine I read years ago and trusted as factual. I quote both passages without comment.
Awake! 8/22 1995.
Although Auschwitz, Buchenwald, Dachau, and Sachsenhausen were names unknown to most people until after World War II, they were well known to readers of The Golden Age and Consolation. The reports of Jehovah’s Witnesses, smuggled out of the camps at great risk and publicized in Watch Tower literature, exposed the murderous intent of the Third Reich.
The Holocaust: A New History (2017), Laurence Rees, pp. 73 and 74.
The Nazis did not hide the concentration camps. Their existence was well known and newspapers around the world carried stories about them. On 1 January 1934, for instance, the Manchester Guardian accurately described the reality of life in the so-called bunker in Dachau... The consequence of works like Im Moerderlager Dachau, and Juda verrecke. Ein Rabbiner im Konzentrationslager, together with articles in the Manchester Guardian and other newspapers, was that the brutal nature of the Nazi regime was known to the world from the beginning.