BMCR 2001.01.19

Roman Fortresses and their Legions. Papers in honour of George C Boon

, , , Roman fortresses and their legions. Occasional papers of the Society of Antiquaries of London, no. 20. London/Cardiff: Society of Antiquaries of London, 2000. xvii, 187 pages : illustrations, maps, plans, portrait ; 27 cm.. ISBN 0854312749

One of the great indicators of Roman imperial policy has traditionally been the movement of the legions. For the ancient policy-makers, individual units were large enough—comprising five or six thousand men, by modern consensus—to be treated as armies in miniature and shunted to trouble-spots as the need arose, or, equally, to be drawn upon, whole or in part (the so-called vexillationes), as the building blocks for expeditionary armies. At the same time, there were sufficiently few units—around 30 for the duration of the Principate—for the destruction of any one to produce an overall imbalance, a cause for distress at the highest level. By the same token, the raising of new legions signalled a major shake-up, indicating a perceived need for extra manpower and implying preparations for conquest.

For present-day scholars, the number of individual legions is small enough to facilitate manageable study while each unit is large enough to produce an abundant epigraphic trail. Then there is the patchwork of literary evidence to be considered—always more ready to mention legions than their smaller, less prestigious counterparts, the auxilia—and the archaeological remains of legionary fortresses. The book under review may be expected to concentrate on this last topic and even to provide a comprehensive survey. However, the particular circumstances of the book’s inception have produced quite a different result.

Arising from a conference in celebration of British archaeologist George Boon’s sixty-fifth birthday in 1992, the book opens with a short appreciation of Boon’s life and career (he died in 1994), followed by a select bibliography of his Roman publications, over 250 papers, notes, reports and monographs which appeared between 1945 and 1997. The third chapter is a contribution by Boon himself on the eighteenth-century French antiquarian, Charles Le Beau. But Boon will be best remembered for his work at Silchester and Caerleon,1 and it is his links with that legionary fortress that suggested the topic for this Festschrift.

The result is a medley of ten contributions covering diverse aspects of Roman military studies. The bias towards Britain (four papers) is unfortunate but entirely justified by the circumstances. Augustan Germany is covered (von Schnurbein), and there are useful surveys of the legions in the East (Parker) and on the Danube (Wilkes). But the absence of Roman Africa is regrettable, as is a survey of the legions on the Rhine; both topics would have made a useful volume indispensable. Equally regrettable is the book’s long delay (the cause is not given) as the papers were evidently submitted in 1994. (Two exceptions: Tomlin’s bibliography lists works up to 1996, Parker’s up to 1998.)

Von Schnurbein discusses fortresses of Augustan date (“The Organization of the Fortresses in Augustan Germany”), noting that their purpose as campaigning bases makes it very likely that they accommodated mixed units. Consequently, “any attempt to recognize the established legionary structure in the camps of the Augustan period is questionable, for strictly speaking there are no Augustan ‘legionary’ fortresses.” Nor can von S. identify any uniformity of shape (“closely adapted to the terrain”), although the strict adherence to a rectangular street grid produces such anomalies as the skewed north gate at Marktbreit, where the via decumana meets the rampart at an angle of around seventy degrees. The theory, first expounded by von Petrikovits, that there may have been a conscious decision to incorporate re-entrant angles finds some support from von S.’s recent work at Holsterhausen2 though he cannot offer a reason for the phenomenon.

Von S.’s comments on the Augustan principia provide a lead into the late Tom Blagg’s essay (“The Architecture of the Legionary Principia“). The basic early design, comprising a colonnaded courtyard and, at the rear, a two-aisled cross-hall with a single range of rooms beyond, is remarkable for the small number of offices thus made available for the headquarters and administration. Von S. observes that the Augustan principia commonly lies back-to-back with the praetorium, raising the possibility that certain administrative tasks usually associated with the former were at that stage handled in the latter. The later separation of the two buildings, which B. dates to around AD 30 on the basis of evidence from Bonn, goes hand-in-hand with a re-designed ground plan in which the courtyard is also surrounded by ranges of rooms. Simultaneously, the central position of the rear range, previously a passage through to the adjoining praetorium, becomes a separate room designated as the aedes signorum (shrine of the standards). B. draws attention to the later “monumentalization” of the principia, and suggests that the late first century rebuilding in stone of original timberwork encouraged elaborate ornamentation. He also identifies a subtle change in function with an increasing emphasis on the aedes and a reduction in the number of individual rooms, representing something of a return to the Augustan plan.

Legionary barrack blocks form the centrepiece of Baatz’s thought-provoking contribution to Vegetian studies (“Vegetius’ Legion and the Archaeological Facts”). It is well-known that cohorts II-X were normally accommodated in blocks of six barracks, one per centuria; Baatz usefully illustrates the phenomenon at Neuss, Inchtuthil, Nijmegen, Caerleon, Lambaesis and (less clearly) Lauriacum. This is, of course, at odds with Vegetius’s peculiar (and plainly erroneous) division of the cohort into five centuriae and one turma (Veg., mil. II.6). But cohort I was structured differently. We know, from Hyginus ( de munit. castr. 3), that it was double strength, but the details have never been clear. Vegetius confuses the issue by claiming that five centurions commanded ten centuries in the ratio 4:2:1.5:1.5:1 (Veg., mil. II.8). Baatz demonstrates that the available archaeological evidence is inadequate to resolve the problem. Only at Inchtuthil are the requisite ten barracks and five peristyle houses obvious. At Lambaesis undifferentiated building phases have confused the plan so that, although five (though perhaps six) houses can be seen, there appear to be no more than eight (and perhaps as few as six) barrack blocks. At Nijmegen there are clearly five houses, but only six of the associated eight strip buildings can be identified as barracks.3 Finally, B. suggests that Vegetius’s curious allocation of first cohort centurions to centuriae may have resulted from a misunderstanding of their varying pay rates.

Pay is only one of the topics covered by Tomlin (“The Legions in the Late Empire”) in an essay which comes hard on the heels of the latest batch of late army monographs.4 T. begins by defining frontier and mobile legions and traces their origins back to the third century habit of moving vexillations around. Considerable space is devoted to discussing the size of the late legion from clues offered by Ammianus Marcellinus and Claudian and from papyrus records of rations, pay and donatives, and T. concludes with a consideration of the late legion’s role in battle. However, in by far the longest essay of the book, there is very little mention of fortresses. The dimensions of four late examples—Kaiseraugst, Noviodunum, Troesmis, el-Lejjun—are mentioned, drawing attention to their greatly reduced size in comparison to their imperial predecessors (2.8ha to 5.6ha, as against 18ha to 20ha; see Coello’s monograph for details and bibliography), but those predecessors often appear to continue into the late period at their original size.

Little is known of the eastern frontier fortresses beyond their outlines, as Parker emphasizes in his essay (“Roman Legionary Fortresses in the East”). But it is noteworthy that the 16.5ha fortresses at Satala and Bostra, for instance, are assumed to have remained in full occupation by their respective legions, XV Apollinaris and III Cyrenaica, into the fourth century. In the absence of excavation one cannot be too dogmatic, but there are no surface indications of diminution. P. runs through the known bases from north to south, noting that several legions were billetted in towns. He is most concerned with his own excavations at el-Lejjun, which, alongside the putatively legionary site at Udruh, provide archaeological evidence in an abundance unknown elsewhere in the east.

Wilkes provides a welcome historical sketch of the legionary movements on the Danube, always a key theatre of war in the Roman world (“Roman Legions and their Fortresses in the Danube Lands [first to third centuries AD]”). A catalogue of the twenty-seven legions known to have been in residence there at some time during the Principate is presented as the first of two appendices. The second comprises details of thirty-two Danubian fortresses or possible legionary sites. W. provides full bibliographic references for these, making his essay a valuable supplement to Ritterling’s Pauly Article “Legio”.

The first of the essays on Britain, Fulford’s thoroughgoing investigation of logistics (“The Organization of Legionary Supply: the Claudian Invasion of Britain”), is built on shifting ground, resting as it does on the following unproven assumptions: that the invasion army comprised four legions accompanied by an equal number of auxiliaries; that each unit organised its own equipment and commissariat; that the army embarked in a single sailing; that only half of the army was actively involved in combat while the other half ensured the security of communications; and that all foodstuffs were imported (although meat “could have been provided locally”). It is F.’s intention, I think, to impress us with the vastness and complexity of the undertaking, but an alteration to any one of his assumptions will bring the entire edifice crashing down. The theoretical basis of his discussion sometimes leads to absurdity: for example, on the subject of the weapons supply he allows each combatant the loss of one ballista bolt per year, but as this leads to unimpressive totals he increases the per capita allowance to 100 bolts per annum; this is meaningless without investigating the likely distribution and use of artillery within the invasion army and the retrieval rate of spent ammunition. The extrapolation of the find of 17 catapult arrow-heads around Hut 37 on Hod Hill to give a site-wide barrage of 2,000 catapult arrows, and hence 40,000 across the twenty oppida that Suetonius mentions is similarly questionable.5

There is a certain amount of overlap between the three remaining essays on Britain. Manning (“The Fortresses of Legio XX“) and Keppie (” Legio VIIII in Britain: the Beginning and the End”) discuss individual units in detail while Hassall (“Pre-Hadrianic Legionary Dispositions in Britain”) traces the movement of the legions according to the opinions of different scholars from 1881 to the present day.

Manning maps out the sequence of bases occupied by legion XX in Britain, following the view which has been orthodox since the 1980s: Colchester-Kingsholm-Usk-Wroxeter-Inchtuthil-Chester.6 Hassall presents a significantly different sequence which merits serious consideration. Advocates of the move, around A.D. 67, from Usk (S. Wales) to Wroxeter, some way to the north, defend it as the result of a domino effect, as legion II Augusta simultaneously moved from Exeter in the far south-west to Gloucester, a close neighbour of Usk. Pursuing a hitherto overlooked suggestion of George Boon and Paul Bidwell that legion II Augusta remained at Exeter, H. suggests a sideways move for legion XX to Gloucester and delays the move to Wroxeter by ten years. He then denies any connection between the legion and the Scottish fortress of Inchtuthil, postulating a direct move from Wroxeter to Chester. These are interesting suggestions, demonstrating the gaps in our evidence.

Keppie gives a full discussion of the early history of legion IX Hispana before addressing the issue of its movements in Britain. The legion’s association with bases at Lincoln and York is not disputed. However, as Hassall reminds us, since the discovery of the so-called vexillation fortresses in the East Midlands there has been a tendency to interpret these as bases for legion IX prior to its arrival at Lincoln. K. makes the interesting observation that purely on epigraphic grounds a case could be made for the IX’s arrival at Lincoln much earlier than the usual date in the early 60s. K. endorses the suggestion of Eric Birley that the legion was later responsible for some sort of base at Carlisle in the north-west of England, though he falls short of placing the entire legion there. (H. has no such qualms.) But it is the disappearance of legion IX that perennially exercises the imagination. K. favours its transfer to Germany under Trajan with a tentative move to the east thereafter which is largely the position adopted by Eric Birley thirty years ago.7

As far as the volume is concerned, the concentration on the legion and, in most cases, some aspect of the fortress provides a unifying theme while the variety of approach ensures that there will be something to interest Roman militarists of all complexions. In particular, both Hassall’s fascinating review of the legionary bases in Britain with the different permutations for contemporary occupation, and Wilkes’s comprehensive discussion of Danubian sites with the background details of their legions, will be indispensable to the respective area specialists. Parker’s discussion of the eastern legions, while only a summary, will be used profitably alongside recent publications by Isaac and Kennedy.8 Von Schnurbein’s essay is important not least in providing an English summary of his own work and that of his German colleagues on the Augustan camp, and the essay by Tomlin provides a welcome restatement of his views on the late army. The contributions of Manning and Keppie conveniently encapsulate the current thinking on their respective legions, while Fulford gives us a glimpse of the complexities of logistical planning. Blagg’s contribution presents the definitive treatment of the legionary principia, but most thought-provoking, perhaps, is the study by Baatz of Vegetius’s antiqua legio, exposing the fallacies that lie at its core and re-opening the debate on the size of the first cohort.


1. On Silchester: Roman Silchester: the Archaeology of a Romano-British Town (London, 1957); The Roman Town of Calleva Atrebatum at Silchester, Hampshire (Reading, 1972); Silchester: the Roman Town of Calleva (Newton Abbot, 1974). On Caerleon: Isca: the Roman Legionary Fortress at Caerleon (Cardiff, 1960; 2nd edn. 1962; 3rd edn. 1972); The Legionary Fortress of Caerleon-Isca: a Brief Account (Cardiff, 1987). Boon contributed entries for Silchester (s.v. Calleva Atrebatum) and Caerleon (s.v. Isca) to The Princeton Encyclopedia of Classical Sites.

2. On re-entrant angles: H. von Petrikovits, Das römische Rheinland. Archäologische Forschungen seit 1945 (Cologne, 1960), 24ff. On Holsterhausen: S. von Schnurbein, ‘Untersuchungen zur Geschichte der römischen Militärlager an der Lippe’, Berichte der Römisch-Germanischen Kommission 62 (1982), 7-101, at p.27. On Marktbreit: M. Pietsch, D. Timpe & L. Wamser, ‘Das augusteische Truppenlager Marktbreit’, Berichte der Römisch-Germanischen Kommission 72 (1991), 263-324, at p.284.

3. On Inchtuthil: L.F. Pitts & J.K. St.Joseph, Inchtuthil. The Roman legionary fortress (London, 1985), 164ff., where it is acknowledged that, far from being the norm, Inchtuthil appears to be the exception. On Lambaesis: Pitts & St.Joseph, op. cit., 165. On Nijmegen: ibid.

4. Tomlin’s bibliography includes: T. Coello, Unit Sizes in the Late Roman Army (Oxford, 1996); H. Elton, Warfare in Roman Europe, AD 350-425 (Oxford, 1996); and P. Southern & K.R. Dixon, The Late Roman Army (London, 1996). On these, see: D. Campbell, “The Later Roman Army”, Britannia 30 (1999), 391-394.

5. In a work which appeared too late for Fulford to utilise, J.P. Roth, The Logistics of the Roman Army at War (264 BC-AD235) (Leiden, 1999), eschews this type of discussion, confining himself to the supply and transport of food, fodder and firewood. Reviewed in: Journal of Roman Studies 90 (2000), 224.

6. This sequence was more or less proposed by Sheppard Frere and refined by Graham Webster. It is, for instance, the sequence which the reviewer adopted in “A History of Legio XX”, in Exercitus: the Bulletin of the Ermine Street Guard vol.1 nos.8-10 (1984/1985).

7. E. Birley, “The fate of the Ninth Legion”, in R.M. Butler (ed.), Soldier and Civilian in Roman Yorkshire (Leicester, 1971), 71-80. Compare Keppie’s slightly different conclusions in “The Fate of the Ninth Legion: a problem for the eastern provinces?” in D. French & C.H. Lightfoot (eds.), The eastern Frontier of the Roman Empire (Oxford, 1989), 247-255.

8. B. Isaac, The Limits of Empire. The Roman Army in the East 2nd ed. (Oxford, 1992), appears in Parker’s bibliography. D.L. Kennedy, “The East”, in J. Wacher (ed.), The Roman World (London & New York, 1990) 266-308, deserves a mention.