Volume 5 of the Official History of Intelligence in the Second World War, Strategic Deception, brings the series to an end. It complements Volume 4 which describes the activities of Nazi agents who had been persuaded to work for the Allies by considering how their work for the Allied side was turned to direct military advantage. Strategic deception depends for its success on the availability of good security and good intelligence. The first three volumes of the series described the intelligence channels that gave the Allies their incomparable insight into enemy capabilities and intentions. The fourth described the high level of security achieved within the United Kingdom. Volume 5 explains how this combination of intelligence and security made it possible to deceive the enemy about the strategic intentions of the Allies, and make them greatly overestimate the resources at their disposal. The authoritative story of such classic deception operations as Operation Mincemeat, which preceded the invasion of Sicily; of the non-existent U.S. Army group that pinned down an entire German Army in the Pas de Calais until Montgomery's forces had achieved a secure foothold in Normandy; and the amazing spoof played on the German intelligence authorities by the great double agent GARBO is at last told from official records.