This chapter introduces the main themes and arguments of the book. It argues that alliances should make problematic instruments for thwarting nuclear proliferation despite the conventional wisdom that they have been partly responsible for keeping the number of states armed with nuclear weapons low. One reason is that they are ultimately unbelievable since states can still decide to forego spending blood and treasure to rescue an ally in dire need. Another reason is that strengthening alliance ties to discourage nuclear proliferation could lead to other undesirable behaviours that might increase the chance of war. In light of this puzzle, this introductory chapter sketches the book’s main argument that alliances can be most useful for preventing potential nuclear proliferation but much less useful for curbing actual nuclear proliferation.
