Victory in World War II depended heavily on Allied successes in espionage and conspiracy. Although individual episodes of intelligence acitvity have been documented, there is no comprehensive account of this vital aspect of the conflict. John Waller has personal experience of espionage, and this work includes new material from recently released documents. In the process the author sheds new light on the ambivalent attitude of Admiral Canaris (head of German Military Intelligence) to Hitler, as well as on the role of Pope Pius XII as the contact point between the German Resistance and the British.