Andrew Park tells the story of the rise and fall of the plebiscite, once seen as a promising democratic solution to international conflict which – more than once – became embroiled in controversy and war in the first half of the twentieth century. The book's central figure is the brilliant but largely forgotten American scholar Sarah Wambaugh, the leading expert on the plebiscite technique whose dramatic career took her to many of the world's political hotspots. The norms she developed for the technique continue to shape how self-determination and popular suffrage in international affairs are thought about and conducted today. In a world where borders are again being redrawn by force and democracy everywhere appears under strain, this book is a timely and compelling reminder that such events are not new.