The First World War is one of the great formative events of modern history. Yet during its centenary, there has been surprisingly little attention to how uncertain entry into the war was in the English-speaking world and how finely balanced the forces for and against intervention were. This talk examines the role of appeals to honour in the decision for war. It pays particular attention to the role of these appeals in convincing radical liberals to accept British intervention – something which they had been successfully blocking until shortly before war was declared. But it also examines parallel appeals in the United States and Australia. It then considers why the language of honour was effective, and whether it still plays a role a century later, before concluding with some possible centennial lessons.