The idea for this book arose six years ago during conversations with Dr Andrew Ayton of the University of Hull, where I had the good fortune to be based throughout the course of my work. Possessing little idea of the immense research task involved, but keen to find out more, I decided to undertake the job of transcribing and computerising the voluminous extant records for military service from the reigns of Edward I and Edward II. The underlying objective was to push back to the late thirteenth century the boundaries of knowledge on the medieval English soldier, and the armies in which he served, thereby adding to Dr Ayton's work (and that of others) on aristocratic warriors and their activities in the period after 1327. That the journey between then and now has for the most part been a smooth one is due in large measure to Dr Ayton's unwavering enthusiasm and belief in the virtues of the project. Moreover, his suggestions on the direction of my research, and his comments on the many drafts of chapters handed to him, have on a practical level been invaluable. This book would be very different had it not been for his input; indeed, it might never have been written at all. Nor would completion of the project have been possible without the financial assistance provided by the arts and Humanities Research Council, whose generous grant of a three-year scholarship I gladly acknowledge.