Professor David Lewis, my supervisor, acted as adviser to this publication: he spent many hours discussing my ideas with me, made valuable suggestions for improvements, and encouraged me. When the final draft was completed in Spring 1994 he read it in its entirety. He was by then very ill and time was precious to him; I shall always be indebted to him for the time he gave to my work. I have dedicated this monograph to David Lewis, an immensely encouraging teacher, a learned scholar and Greek historian with a vast knowledge of the history of ancient Persia, but above all, a kind man.
This volume is based on my doctoral thesis submitted to the Faculty of Literae Humaniores at the University of Oxford in Trinity Term 1991. I wish to thank the committee of the series of Oxford Classical Monographs who accepted this book for publication. In particular I would like to thank the copy-editor, John Cordy, for the considerable care and skill with which he edited the manuscipt.
Many scholars were generous with time and advice, and I am grateful for their assistance. My examiners, Jeremy Black and Robin Lane Fox, discussed a number of problematic issues with me. Amélie Kuhrt, Jeremy Black, and Seamus Ross read drafts of separate chapters and provided helpful comments. Matthew Stolper offered useful suggestions. The Oriental Institute, Chicago, generously provided the University of Oxford with a copy of Hallock's manuscript of unpublished Fortification texts which were of great assistance to this study.
A British Academy Postdoctoral Fellowship gave me the opportunity to prepare this publication under the best circumstances. The fellowship is held at St Hugh's College.