Achtung – Panzer! (English: "Attention, Tank!" or, more idiomatically, "Beware the Tank!") by Heinz Guderian is a book on the application of motorized warfare. First published in 1937, it expounds a new kind of warfare: the concentrated use of tanks, with infantry and air force in close support, later known as Blitzkrieg tactics. The book also argues against the continued use of cavalry given the proven effectiveness of the machine gun, and advocates replacing the cavalry with mechanised infantry. It was never properly studied by the French or the English general staff, both of whom helped introduced the tank.^[1]

The first half of the book focuses on the advent of positional or 'trench warfare' in World War I, and the subsequent development of the first tanks. Here Guderian outlines the development of tanks and tank tactics throughout the Great War and during the interwar period. Later he discusses the effects of the Treaty of Versailles upon the German armed forces before detailing the recovery from the setbacks the Treaty caused in terms of development of mechanised forces. Guderian concludes by promoting the further development of the German tank force and providing suggestions concerning the future application of tanks and their relationship with other arms.^[2]