I have a book by the man who inspired the writing of 'Die Moorsoldaten', the original song, Wolfgang Langhoff. He was an inmate of the Boergermoor concentration camp in 1933/34 and wrote his book in 1935. He survived and went on to become one of the leading lights in GDR theatre, and died in 1966.
I've just copied the account of how and why the song was written into my PC, but translating it will take a little more time. Would anyone be interested in the translation? Otherwise I'm not going to do it.