This Volume, out of four, of the history of the North American Aviation P-51 Mustang and P-82 Twin Mustang, takes you from the first steps of the North American Aviation Corporation to the end of the evolution of those two aircraft, through the British decision to award the development of this exceptional fighter to NAA. It also provides the production history with links between military serials and model blocks. Richly illustrated, this volume gives the background information and overview required to enjoy the operational history detailed in Volumes II and III.