English describes the development of a uniquely Canadian selection system that attempted to match the aptitudes of aircrew candidates to the duties they would perform and the evolution of the RCAF's training program from a haphazard system with enormous attrition to one that became the model for many modern systems. He traces the development of aviation psychology and the treatment of psychological casualties of air combat. English pays particular attention to the LMF controversy and the RCAF's response as well as the effect of morale and leadership on the psychological well-being of, and casualty rates among, Royal Air Force and RCAF bomber squadrons. In exploring the human dimension of air warfare, an issue that has been widely overlooked in military literature, English demonstrates that personnel considerations have at least as much influence on the effectiveness of air forces as material and technological factors.