This chapter focuses on the proliferation of weapons of mass destruction (WMD). It examines the patterns that can be observed in the spread and use/non-use of nuclear, chemical, and biological weapons since 1945, how nuclear weapons have changed world politics, and whether non-proliferation efforts have been successful. The chapter first provides an overview of WMD technology and its spread before discussing biological and chemical weapons. It then considers theoretical debates about nuclear proliferation and the evolution of non-proliferation efforts. Two case studies are presented, one dealing with the nuclear programme of North Korea and the other looking at the nuclear programme in Iran.
