Today, the United Nations marks the International Day of Commemoration for the Victims of the Crime of Genocide. The designation of genocide as an independent crime under international law – alongside war crimes and crimes against humanity – was in reaction to the horrors of the second world war, when Nazi Germany, driven by ideas of “Aryan superiority” and a desire for “racial purity”, pursued an extermination campaign against several peoples they deemed inferior. Roma and Sinti, Slavs and, most extensively, Jewish people, were brutally persecuted. Millions died in concentration camps – starved, worked or gassed to death – alongside...