The Strategic Defense Initiative (SDI) holds the potential to alter the U.S. approach to strategic policy modestly, radically, or not at all. A radical departure from policy is likely to provide more fertile ground for ballistic missile defense (BMD) deployment than is modest change. Indeed, it will be difficult to sustain an argument for very limited BMD protection. However, the proper combination of BMD deployment and arms control could provide an excellent basis for a radical departure from current policy—while minimizing or eliminating many of the problems that SDI critics foresee.