America and its allies are entering a period of nuclear uncertainty

IS DETERRENCE easy or hard? That simple question has been at the heart of nuclear strategy for almost 80 years. For Bernard Brodie, an early nuclear theorist, the bomb had created a stable balance of terror. The precise number and variety of weapons was less important than the fact that they existed. His colleagues Herman Kahn and Albert Wohlstetter disagreed. The balance was “precarious”, they retorted, and required careful and continuous attention to metrics such as the relative damage that each side would suffer in a nuclear exchange and thus to the relative size and quality of their respective arsenals.