The possibility of large reductions of nuclear weapons poses fundamental questions about the purpose of nuclear weapons. Why have some countries chosen to acquire nuclear weapons? How--and why--have these decisions been maintained over time? Why have some countries elected tp approach, but not cross, the nuclear threshold? This book examines the similarities and differences in political approaches to nuclear weapons both within and among three groups of countries: nuclear, non-nuclear, and threshold. Providing insight into the impact nuclear weapons have on national and international security, this analysis offers a comprehensive reassessment of the concept of nuclear security.