Achieving an end-state of "zero" has emerged as an important policy goal for a number of 21st Century challenges. The most prominent example is the "Global Zero" campaign to eliminate nuclear weapons. To stand any chance of getting near to zero, nuclear weapons must be marginalised in military and security doctrines. That means creating international norms and, if feasible, agreements that until nuclear weapons are universally prohibited by treaty, their use will be treated as a crime against humanity. Dr Johnson considers how the problems of doctrine and use could be addressed.