I've been reading through Richard Evans's trilogy, and am currently on the last book ('the Third Reich at War'). I've been reading about the atrocities they committed in the name of the 'Aryan race'. But how did it come about that the antisemitism of the Weimar era led to the attempt to kill all the Jews in the Reich?
Was it 'just following orders'? Was it due to the antisemitic propaganda?
I appreciate that the Soviets etc were also barbaric in their treatment of civilians - so what makes an entire army and regime participate in the slaughter of civilians? (As far as I know, it wasn't just the SS, the Wehrmacht was also involved)
To begin with, violent antisemitism and anti-Judaism in Germany dates back to the middle ages at least. A general fear, mistrust, or dislike of Jews has also been common throughout Europe from the middle ages until present day. However, your specific question about why Germans felt it necessary to exterminate the Jewish "race" is something that transcends a simple cause-effect relationship that can be gleaned from documentary evidence. The holocaust and genocide in general are very complex and I urge you to study them as a general concept. However, I think you might be able to find some answers in The Path the Genocide by Christopher Brown.