Nuclear deterrence, though much changed, is as relevant today as ever. If its material and manner of application have evolved, its usefulness has not and it is, in a word, just as necessary today as it ever has been—perhaps more so—and will remain so for the foreseeable future. Nevertheless, the question of employment of nuclear weapons needs to be thoroughly reviewed, with emphasis on the characteristics that future nuclear weapons should have and the doctrine for their use. The balance to be struck between nuclear deterrence and deployment of conventional forces on one hand, and missile defence on the other, is also discussed, as is deterrence in a broader sense—how it might operate in a variety of circumstances, given the absence of structures comparable to those of the Cold War era, and how to formalise the conditions.