Twenty years ago it would have been unthinkable for a historian to combine the National Socialists’ murderous excesses and programme of extermination with Bolshevik atrocities in a single history. He would have been accused of ‘relativising’ one set of murderous crimes by relating it to the other. The comparison does indeed have a relativising effect in that it puts the events in a new light and so makes them, for the first time, comprehensible. But at that time, when historians still treated all historical questions as moral ones, nobody wanted to anything to do with that comparison because it ran counter to the political will. You could compare anything with anything, except the Holocaust, which had to remain unique. Nobody could write about the excesses of Stalinist violence without acknowledging that the Nazi murder programme was unique. Nonetheless everybody knew, even then, that uniqueness cannot be established without comparisons and contrasts.1 Since then, a view that used to be considered shocking has become a self-evident: no examination of state atrocities is now possible without a comparative element. But this change can also serve political ends: the Holocaust has become the sole yardstick for measuring state-organised crimes of violence. It seems that such crimes can only be taken seriously if they are comparable to Nazi atrocities.2