The Grand Strategy of the Roman Empire From the First Century CE to the Third REVISED AND UPDATED EDITION Edward N. Luttwak |( >1111 ! I • 'i >( II! I imriMlx I ’less © 1976. ' 979i 2016 Johns Hopkins University Press All rights reserved. Published 2016 Printed in the United States of America on acid-free paper 98765432 1 Johns Hopkins University Press 2715 North Charles Street Baltimore, Maryland 21218-4363 www.press, jhu.edu Library of Congress Cataloging-in-Publication Data Names: Luttwak, Edward, author. Title: The grand strategy of the Roman Empire : from the first century CE to the third / Edward N. Luttwak. Description: Revised and updated edition. I Baltimore .- Johns' Hopkins University Press, 2016. I Includes bibliographical references and index. Identifiers: LCCN 2015030270I ISBN 9781421419442 (hardback) I ISBN 9781421419459 (paperback) I ISBN 9781421419466 (electronic) Subjects: LCSII: Rome—Army. I Strategy. I Military history, Ancient. I BISAC: HISTORY / Ancient / General. I HISTORY / Military / Strategy. Classification: LCC U35 .L8 2016 I DDC 355/033537—dc23 LC record available at http://lccn.l0c.g0v/2015030270 A catalog record for this book is available from the British Library. Special discounts are available for bulk purchases of this book. For more information, please contact Special Sales at pio-pi6-6p^6 or speaalsales®press .jhu.edu. Johns Hopkins University Press uses environmentally friendly book materials, including recycled text paper that is composed of at least 30 percent post-consumer waste, whenever possible. Contents List of Maps, Figures, and Tables vii Preface to the 2016 Edition ix Preface to the First Edition xv Acknowledgment xvii Introduction 1 1 The Julio-Claudian System: Client States and Mobile Armies from Augustus to Nero 6 The System in Outline 10 / The Client States 19 / The Management of the Clients 28 / The Tactical Organization of the Armv 42 / The Strategic Deployment of Forces 50 / Conclusion 53 2 From the Flavians to the Sever!: “ Scientific” Frontiers and Preclusive Defense from Vespasian to Marcus Aurelius 56 The System in Outline 60 / Border Defense: The Tactical Dimension 67 / Border Defense: The Strategic Dimension 89 / The Decline of the Client System 125 / The Army and the System 132 / Conclusion 144 3 Defense-in-Depth: The Great Crisis of the Third Century and the New Strategies 146 The System in Outline 149 / The Changing Threat 166 / The New Borders of the Empire 176 / Walled Towns and Hard-Point Defenses 182 / Border Troops 195 / Provincial Forces 199 / Central Field Armies 207 / Conclusion 216 Epilogue. The Three Systems: An Evaluation 219 Appendix. Power and F'orce: Definitions and Implications 223 Notes 229 Bibliography 251 Index Ahj Maps, Figures, and Tables MAPS 1.1 The Empire in 23 CK 12 1.2 The East under the Julio-Claudians 30 1.3 The German Problem, 6-16 CE 36 2.1 The Frontiers in the Second Century 64 2.2 Strategic Mobility in the Roman Empire 92 2.3 The Wall Frontiers of Roman Britain 104 2.4 The Advancing Frontier in Germany 108 2.j The Second-Century Frontiers in Europe 112 2.6 The Dacian Conquest 116 2.7 The Strategic Importance of Armenia 120 2.8 The Parthian Empire and the Roman East 123 3.1 The Great Crisis of the Third Century 170 3.2 The Fontiers of the Tetrarchy and the New Provinces 180 3.3 The Defense-in-Depth of the German Frontier 186 3.4 Defense-in-Depth: Augusta Libanensis (Only Attested Units Shown) 208 FIGURES 1.1 Roman Unit Establishments in the First and Second Centuries C E 14 1.2 Two .Models of Empire 22 2.1 Models of Frontier Organization I 70 2.2 Models of Frontier Organization II 72 2.3 Hadrian’s Wall: The Barrier Elements 79 2.4 The Tactics of Forward Defense 86 3.1 Operational Methods of Border Defense: Elastic Defense 160 3.2 Operational Methods of Border Defense: Defense-in-Depth 762 3.3 Operational Methods of Border Defense: Forward Defense 164 3.4 The Changing Pattern of Roman Fortification 188 TABLES 2.1 Legionary Deployments, 23 C E to 192 C E 95 :.2 Auxiliary Troops in Lower Germany 97 Li 1 ) ist ri I union of Troops: Frontier and Field Armies in the East and West 217 Preface to the 2016 Edition When the first edition of this book was published— it w'as nothing more than the text of a Johns Hopkins University dissertation, quickly written by a young husband and father in a hurry— it immediately attracted inordinate, wholly unexpected attention. A first wave of reviews wras followed by journal articles, lengthy monographs, and then entire books, an unending flow' in several lan­ guages that soon exceeded my ability to keep up. Oddly enough, from the start this book was both highly praised and harshly condemned for exactly the same thing: my attribution of a “grand strategy” to the Romans, indeed three of them in succession over as many centuries: the first expansive, hegemonic, and reliant chiefly on diplomatic coercion; the second meant to provide security even in the most exposed border areas, in part by means of fortified lines whose remains are still visible from Britain to Mesopo­ tamia; and the third a defense-in-depth of layered frontier, regional, and central reserve forces that kept the western empire going till the fifth century and the eastern empire for much longer. There was a definite pattern in the reviews that appeared originally and in the articles and monographs that kept coming. The two most senior scholars of highest reputation, holding chairs at Oxford and Harvard, respectively, made light of any errors and omissions to instead praise the book unreservedly for uncovering the overall logic that explained a great many Roman doings and undoings in wur and diplomacy, which previous scholarship had diligently described but not explained. They even predicted (accurately) that this book would transform Roman frontier studies.1 But younger scholars still making their w'ay w'ere more critical, some harshly so. They started by pointing out t he absence of any contemporary references to strategic planning, and the absence of any documents describing imperial strategy at any point in time. \nd they proceeded to argue that no such documents could possibly have existed because Romans never had military or civilian planning staffs, which m any case would have lacked such elementary tools as accurate maps. These w ere not unreasonable objections (though I and others have argued otherwise, as noted below), but the vehement manner in which they were •nit anced st rough suggested that some scholars were offended hv the very idea X Preface to the 2016 Edition that Roman men could transcend the mindless pursuit of personal glory to think rationally at all. One scholar started her critique with an account by Herodian (1.6.5-6) in which we encounter a capricious Commodus and his spoiled friends idly conversing about the merits of continuing to fight the Quadi and Alarco- manni on the Danube frontier.2 The implication is clear: Roman emperors were just foolish boys striking poses— exemplars of the mindless men of any age. In such depictions, one cannot recognize the emperors—yes, even Commodus— officials, and soldiers who devised, built, and maintained the structures of im­ perial security that long enabled obedient, tax-paying subjects and their obedi­ ent wives to raise crops, livestock, and children in considerable safety from marauders, raiders, and invaders even on the outer edges of the most exposed frontier lands. One may wonder why that author did not start with Augustus, the magisterially sly inventor of the principate, or with Tiberius at the Rhine crossing, standing in the freezing dawn to personally inspect the soldiers pass­ ing by to ensure that they were not overloaded with gear and rations, or with the indefatigable Hadrian, reviewing troop exercises in professional detail very far from Rome, or for that matter with Gaius (“ Caligula”), when he decided that crossing the channel was not a good idea after all. Actually it is far better to simply leave aside our tenuous evidence on the proclivities of individual em­ perors, because the empire was an immeasurably larger reality than any of them. It encompassed countless nameless administrators and officers efficient and honest enough to recruit, train, equip, and supply hundreds of thousands of troops, including the shivering sentries who tenaciously guarded Hadrian’s Wall and the auxiliary cavalry that daily patrolled desert frontiers in the ex­ tremes of summer heat, all of them doing their duty day after day, week after week, month after month, year after year, century after century. That was the empire, not the reported or misreported musings of Commodus and his friends. Alore soberly, if still insistently, a work seemingly written in direct response to mine maintained that the Romans -were incapable of strategic thinking and could not even lay out frontier defenses coherently—which then forced the author (and several others who followed him) to explain even conspicuously systematic fortifications extending over vast distances as nothing more than local improvisations.3 Another scholar pointed out that the Romans lacked any formal training in statecraft, strategy, or foreign policy, and were thus inca­ pable of making strategic decisions in anv case. In sum, these critics berated me for having interred comprehensive (“grand” ) strategiex tb.il could not pox Preface to the 2016 Edition xi sibly have existed because the Romans were intellectually incapable of any such thing; hence, they argued, the archaeological, epigraphic, numismatic, and narrative evidence that I assiduously cited was simply irrelevant. Fittingly, scholars in a middle category, neither junior nor eminent, paid the book the compliment of exceptionally extended attention, while being critical of its overall approach to a lesser or a greater extent.4 Thus one scholar reviewed the book at very great length in the Journal of Roman Studies,5 identi­ fying a number of outright errors and challenging the entire notion that the Romans could have planned and executed any “grand strategy,” lacking as they did a planning staff or general headquarters.