Today, the Nazi persecution of Jewish people is widely viewed through the prism of the death camps: places such as Treblinka, Sobibor and Auschwitz. Yet before Auschwitz was even conceived as a centre of mass murder, more than a million people had been killed across eastern Europe. This is the story of the early stages of the Holocaust, when a campaign of appalling abuse and brutality became an explicit policy of annihilation. BY JAMES BULGIN