After the narrow defeat of their U-boat fleet in the First World War, the German Navy analysed their experiences and devised new theories and plans for a future conflict. The principal result of this study was the development of the daring concept of Rüdeltaktik which involved coordinated pack attacks on the Allied convoy systems that had proved so successful in defence. Dönitz was one of the architects of this new scheme, and his favoured method was the surfaced night attack, the U-boats shadowing the convoys for some time, communicating the position of their quarry and then converging from the surrounding ocean areas for "the kill". The perfect boat to implement this doctrine had to have certain characteristics: it required an effective operational range and the levels of speed and armament usually associated with large boats; and it had to be highly manoeuvrable with a fast dive - a factor normally exhibited by smaller boats It needed excellent communications and, above all, it had to be easy to build because a great many were needed. Armed with such a weapon, Dönitz was convinced that, given the will, Germany could win any tonnageschlact (tonnage battle) in the Atlantic. It was the Type VII U-boat that largely fulfilled this role. Over 700 examples of this superb submarine were built, making it by far the most numerous type of U-boat and fully deserving of this study. Robert C. Stern looks in detail at how the various technological elements of this advanced weapons system worked and how the crewmen operated to maximise its effectiveness in action. He traces the development and design of the class together with the crucial offensive and defensive components it took to sea: torpedo and gun type; radio, hydrophones, radar decoys, and sonar counter-measures; mines; and a host of other innovative items. Interviews with U-boat veterans and access to plentiful naval records have given the author the means to provide a fascinating insight into both life aboard a cramped vessel (food storage, sanitation, etc.) and the practical methods used both to track and destroy the enemy and to avoid his often fatal searches. The book is illustrated with a marvellous selection of photographs, some 160 in total, and several dozen line drawings. With its appendixes on paint schemes, boats built and a profile of Dönitz, this is a valuable contribution to the study of the U-boat arm, which will be warmly welcomed by naval enthusiasts.