For 10 points, identify this massacre of 355 Italians by German police in a cave in Rome.
One book about this event is an oral history entitled The Order Has Been Carried Out. An earlier book about this incident by Robert Katz led to an unsuccessful libel lawsuit concerning his allegations that Pope Pius XII failed to prevent it from taking place. The perpetrators of this incident were originally given the impossible order to murder ten Italian political prisoners for every German killed in a guerrila attack. As a result, local Jews were also killed to reach the requisite number. In order to avoid logistical issues associated with burial, this event took place (*) underground, after which its location was sealed. For 10 points, identify this massacre of 355 Italians by German police in a cave in Rome.
One book about this event is an oral history entitled The Order Has Been Carried Out.
Fosse Ardeatine massacre (or Ardeatine caves massacre)