History has accused wartime pontiff Pius the Twelfth of complicity in the Holocaust and dubbed him "Hitler's Pope." Riebling shows that, in reality, Pius ran the world's largest church, smallest state, and oldest spy service. Skimming from church charities to pay covert couriers, and surreptitiously tape-recording meetings with top Nazis, Pius played sent birthday cards to Hitler-- while secretly plotting to kill him. Fearing that overt protest would impede his covert actions, he muted his public response to Nazi crimes.