After the First World War, many countries faced the question of ‘what to do with the tank next?’ The tank had undoubtedly proven its worth on the battlefield, but not everyone was convinced, particularly because nobody had yet established a proper doctrine for how to deploy it in a future conflict. The interwar period shows that each country shaped the future deployment of the tank and the corresponding tank types in its own way. These were not arbitrary exercises, as investments in tank development and production were substantial, and switching to a different doctrine and tank type was not an option. This book reflects this search. However, the fact that the Germans ultimately found the right combination of doctrine and tanks with the phenomenon that was ‘Blitzkrieg’, does not detract from the interesting ideas, efforts and choices of other countries. The career of Heinz Guderian beautifully illustrates all these discussions cumulating in the development, rise, and fall of German Panzerwaffe before and during the Second World War. For this reason, he forms the central thread of this book, around which the development of the tank is wrapped.