The findings of a study on military research and development. An attempt was made to discover what kinds of policies are most effective in providing the military services with new weapons. Based on an examination of past programs, this study investigated the development histories of many of the postwar fighters and bombers, most of the postwar engines, and all of the postwar bombing-navigation systems. Most of the cases considered were taken from the history of research and development in the Air Force, although the findings are relevant to all military R&D. In particular, the general nature of military R is discussed, the shortcomings of some present development policies are indicated, a more fruitful approach to weapon-system development is suggested, and the question of providing technological building blocks for future weapons is considered.