This work examines the evolution of the RAF's operational requirements for its home defence air force - for bombers to mount a deterrent counter offensive and for fighters to provide direct defence of Britain. It discusses the management processes, policies and decisions relevant to operational requirements on the basis of a detailed study of Air Ministry papers of the time. By tracing the development of operational requirements, the author exposes the thinking behind the RAF's quest for effective fighter and bomber aircraft. He describes the ideas and concepts of air warfare that were adopted in the 1920s, and shows how these evolved into the Air Staff's requirements for the aircraft which the RAF entered and fought in World War II.