In 1945, following the liberation of the German concentration camps by British and American armies, photographs and newsreels starkly revealed that a new level of horror had been reached. Susan Sontag later wrote: One’s first encounter with the photographic inventory of ultimate horror is a kind of revelation, the prototypically modern revelation: a negative epiphany. For me, it was photographs of Bergen-Belsen and Dachau…. Nothing I have seen -- in photographs or in real life -- ever cut me as sharply, deeply, instantaneously (Susan Sontag on Photography, 1990). The question asked in bewilderment was, “How could people do this?”, without ever receiving an adequate answer.
George Kren (1998) studied this question.