This volume explains how a successful combination of security and intelligence made it possible to deceive the German High Command as to the strategic intentions of the Allies and make them greatly overestimate the resources at their disposal. It provides the authoritative story of such classic deception operations as Operation Mincemeat, which preceded the invasion of Sicily; of the non-existent US Army Group that pinned down an entire German Army in the Pas de Calais and of the spoof played on the German intelligence authorities by the double-agent GARBO. The author also wrote Disengagement in Europe, The Franco-Prussian War, The Theory and Practice of War, War in European History, The Causes of War and Clausewitz.