How much did World War II German soldiers know about the Holocaust? Publicly, many of them denied knowledge. But a long-lost cache of secret recordings that the British intelligence service made of German prisoners of war show that, in private, they chatted openly and casually about mass-murdering Jews. Read some of the most chilling conversations, collected in “Soldaten: On Fighting, Killing, and Dying: The Secret WWII Transcripts of German POWs,” by Sönke Neitzel and Harald Welzer, who rediscovered and analyzed the transcripts. If you’re an American reading this item, I wouldn’t feel too smug. Many of us still don’t seem to know that the United States was founded on a genocide: of Native Americans.