[en] This paper argues that deterrence is the best that can be done in a world of sovereign states, but deterrence cannot last forever, and nothing less than unconditional assurance is acceptable when survival is at stake. To accumulate more or better weapons tends to accelerate the arms race, raise tension levels, and produce insecurity. And yet to get rid of weapons by unilateral or even agreed means tends to tempt international adventurism, to arouse fears about vulnerability and weakness, and thus to produce insecurity. As a result, an uneasy compromise has evolved since Nagasaki. Its components are a continuous flow of new weapons systems, more or less matched by a continuous effort to manage risks in various ways including arms control arrangements, summit meetings, and various efforts at command and control. One of the most massive efforts at reassurance has been associated in the last few years with the Strategic Defense Initiative (SDI), the ideal war-maker's approach to nuclearism by way of the most elaborate technological fix ever conceived