Using a combination of new perspectives and new evidence, this book presents a reinterpretation of how 21st Army Group produced a successful combined arms doctrine by late 1944 and implemented this in early 1945. Historians, professional military personnel and those interested in military history should read this book, which contributes to the radical reappraisal of Great Britain's fighting forces in the last years of the Second World War, with an exploration of the reasons why 21st Army Group was able in 1944–45 to integrate the operations of its armour and infantry. The key to understanding how the outcome developed lies in understanding the ways in which the two processes of fighting and the creation of doctrine interrelated. This requires both a conventional focus on command and a cross-level study of Montgomery and a significant group of commanders.