Political decision theory provides a framework for evaluating three approaches to military research and development: offensive weaponry intended for deterrence, the Strategic Defense Initiative and other weaponry intended fordefense, and cutbacks designed to slow the research and development treadmill. Large-scale R&D does not protect against most of the risks facing national security. Nor does an R&D-intensive approach provide the flexibility necessary to adjust military policy in light of rapidly changing international conditions. Considering all factors together, there is a strong theoretical (...) case for placing sharp constraints on military innovation, not just on the quantities of weapons deployed. (shrink)