The book begins by placing the reader within the British Empire’s “crisis” of the early twentieth century, through the eyes of a few observers trying to warn their contemporaries of a forthcoming doom. It acquaints the reader with the book’s central contention – that this sense of crisis created an empire–wide preoccupation with security that sparked militarization and realigned imperial politics – before providing an overview of the book’s structure, sources, and methodology. The introduction will also contextualize this moment of crisis with some others in British imperial history, before transitioning the reader into the book’s narrative beginning with the South African War.