I have in many places been glad to acknowledge my indebtedness to my predecessors in this field of study, who in one branch of the subject or another have removed so many difficulties from my path. To two scholars, however, my debt is too extensive and general to have received adequate recognition in the footnotes. Mommsen’s article, ‘Die Conscriptionsordnung der römischen Kaiserzeit,’ was written thirty years ago; I have, I hope, been diligent in collecting the evidence which has since accumulated, but I have found little to induce me to leave the path indicated by the founder of the scientific study of the Roman Empire. I owe much to Professor A. von Domaszewski’s ingenious and comprehensive work, _Die Rangordnung des römischen Heeres_, and feel my obligation to its learning and suggestiveness none the less that I have sometimes been compelled to differ from the conclusions stated in it. I am also deeply indebted to Professor Haverfield for constant encouragement and much valuable criticism, and can only wish that this essay were a more adequate testimony to the value of his influence upon the study of Roman history at Oxford. I desire also to express my gratitude to my colleague, Mr. N. Whatley, of Hertford College, for reading this essay in manuscript, and making many valuable suggestions. G. L. CHEESMAN. NEW COLLEGE, OXFORD. CONTENTS PAGE INTRODUCTION THE MILITARY REFORMS OF AUGUSTUS 7 THE AUXILIA DURING THE FIRST TWO CENTURIES A.D. SECTION I. THE STRENGTH AND ORGANIZATION OF THE AUXILIARY REGIMENTS 21 SECTION II. RECRUITING AND DISTRIBUTION 57 SECTION III. THE USE OF THE AUXILIA FOR WAR AND FRONTIER DEFENCE 102 SECTION IV. ARMS AND ARMOUR 124 CONCLUSION THE BREAK-UP OF THE AUGUSTAN SYSTEM 133 APPENDIX I 145 APPENDIX II 170 INDEX 191 ILLUSTRATION TOMBSTONE OF C. ROMANIUS OF THE ALA NORICORUM (by kind permission of the authorities of the Stadtmuseum, Mainz) _Frontispiece_ LIST OF ABBREVIATIONS EMPLOYED The _Corpus Inscriptionum Latinarum_ is referred to simply by the numbers of the volumes without any prefix. The military diplomata (D) are referred to by the revised numbering given in the supplement to the third volume of the _Corpus_. _Eph. Ep._ = _Ephemeris Epigraphica._ _A. E._ = _L’année épigraphique_, edited by MM. Cagnat and Besnier. _I. G. R. R._ = _Inscriptiones Graecae ad res Romanas pertinentes_, edited by Cagnat. _B. J. B._ = _Bonner Jahrbücher_, the periodical of the _Verein von Altertumsfreunden im Rheinlande_. _W. D. Z._ = _Westdeutsche Zeitschrift._ _B. G. U._ = _Ägyptische Urkunden aus den königlichen Museen zu Berlin._