I OWE THANKS to many people for the help they have given me in preparing this book. The meetings of De Re Militari, the Society for Medieval Military History, have provided enormous stimulus over many years. More particularly, I would like to thank Clifford Rogers and Kelly DeVries, my colleagues on the editorial board of the Journal of Medieval Military History, for their kindness, patience, and great learning. Professors Bernard and David Bachrach have been a rich source of ideas. My colleagues in the History Department of Swansea University, Professor Dan Power and Dr. Simon Johns, have been enormously helpful. I can only admire the scholarly learning of Professor Matthew Strickland, to whose work I owe a very great deal. Dr. Alan V. Murray has been most generous in sharing knowledge and ideas. I owe a great deal to Dominique Barthélemy, whose knowledge of medieval France is remarkable. Federico Canaccini very kindly granted me the benefit of his learning, while Peter Herde made me think again about the Battle of Tagliacozzo.

Much of this book has been written during the extraordinary restrictions imposed by Covid-19. In spite of this, my family, and especially Angela, my wife, have coped with my struggles against these circumstances. Last, but not least, I must thank Anna Henderson of Arc Humanities Press, for all her help and the occasional – albeit tactful – prods, which have kept me going.