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 argues for the use of tanks and motorized support vehicles in mobile warfare, later known as Blitzkrieg tactics. The ideas presented in the book heavily influenced the military actions of Germany during the Second World War.
The first half of the book focuses on the advent of positional or 'trench warfare' in the Great War, and the subsequent development of the first tanks. Guderian describes the numerous technological and tactical developments regarding tanks, throughout the Great War and in the inter-war years. 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. He then goes on to describe his beliefs about the future application of tanks in warfare and their relationship with other arms.