Rivers As Boundaries in the “Empire Without End”
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Rivers as boundaries in the “Empire without end” An ancient perspective on a modern debate Fig. 1: Caesar’s Rhine Bridge, John Soane (1814). Pelle Wijker Student number: 10411453 Telephone number: --- E-mail address: --- Master’s thesis Research Master’s, History Universiteit van Amsterdam Supervisor: prof. dr. E.A. Hemelrijk Second reader: dr. J.A. van Rossum 14 July 2014 1 Contents General introduction Introduction p. 4 The problem of sources p. 8 Boundaries and their definition p. 10 Landscape and culture p. 11 I. Rivers in Roman religion Introduction p. 14 Sacred water p. 15 River gods p. 20 River crossings and religious boundaries p. 27 Conclusion p. 31 II. Rivers as military and political boundaries Introduction p. 34 The military uses of rivers p. 35 Political boundaries and the borders of the Empire p. 39 Imperium sine fine p. 44 Conclusion p. 48 III. The Rhine Introduction p. 50 Pater Rhenus p. 51 The Rhine as frontier p. 55 Crossing the Rhine p. 59 Conclusion p. 65 General conclusion p. 68 Bibliography p. 70 2 3 General introduction Introduction “Do rivers make good frontiers?” asked the British historian Boris Rankov, provocatively, in a lecture given at a congress of 'Roman frontier studies' in Pecs, Hungary in 2003.1 To his audience, the question will have been a familiar one; indeed, it has been asked and answered, sometimes explicitly and often implicitly, in scholarly works on the frontiers of the Roman Empire for several decades now. To understand why this question was foremost in their minds, one has only to glance at a map to see that the borders of the great Empire, as traditionally described, were for the greater part of its history located largely along three major rivers: the Rhine and Danube in the north, and, to a somewhat lesser extent, the Euphrates in the east. Only a number of small areas in the north and east (Britain across the sea and the so-called Agri Decumates between the Rhine and Danube), as well as the long African border on the Sahara desert, appear to have been 'dry frontiers'. Too much stock should not perhaps be placed in these maps we find in schoolbooks and on Wikipedia. Although their function, meaning, and apparent veracity are obvious to the modern observer, it must not be forgotten that the Romans themselves did not have access to maps of this sort.2 As both a reason for and a consequence of this fact, their understanding of the world, their Empire, and its borders, may well have been very different from our own, and rather more complex than these lines on a map might suggest. Indeed, this is what many historians have argued over the past decades.3 Nevertheless, a great many passages in Roman texts do in fact refer, quite simply and explicitly, to the great rivers as demarcating the limits of the Empire.4 Perhaps most famous among these is the assertion by Tacitus that, thanks to the conquests made by Augustus, the Empire was “enclosed by the Ocean or distant rivers”.5 The complex debate on the river frontiers of the Roman Empire, in which this thesis is engaged, can perhaps be boiled down to the essential question of how seriously and how literally we ought to take statements like this. Rankov's answer to his own titular question was a resounding “yes”: rivers do make good frontiers, and the Rhine and Danube were indeed the linear borders of the Empire. In other words: Tacitus was spot on. This may have come as somewhat of a surprise to his colleagues, however, because over the past few decades a fairly broad consensus has emerged in the field which holds that rivers are poor lines of defence, and that the great northern rivers functioned not as boundaries or military frontiers, but as lines of communication and transport in a broad and vaguely defined 1 Rankov (2005). See also Austin & Rankov (1995), p 173-180. 2 Nicolet (1991), Brodersen (2001), Salway (2001). 3 See below. 4 See especially Chapter II, “Political boundaries and the borders of the Empire”, below. 5 Mari Oceano aut amnibus longinquis saeptum imperium. Tacitus, Annals 1.9 (English transl. J. Jackson 1925-1937). 4 'frontier zone'.6 According to this theory, passages by Roman authors that seem to contradict this interpretation by referring to the Rhine or Danube as a meaningful boundary, like Tacitus' cited above, reflected little more than literary tropes, and any reference to rivers as boundaries were made out of convention and bureaucratic convenience – after all, the visible line of a river is simply an easy line to point to and describe – rather than having any stronger meaning.7 This consensus, which can still in some ways be recognized in Brian Campbell’s recent benchmark work on the subject of rivers in the Roman Empire, Rivers and the power of ancient Rome,8 is the product of a debate that can be traced to the highly influential yet controversial work of American strategist Edward Luttwak in the 1970's. In his book The Grand Strategy of the Roman Empire he attempts to discern a consistent frontier strategy in three centuries of Roman imperial policy. The great rivers were a key part of this strategy; according to Luttwak, the emperors understood rivers to be rational military boundaries, and aiming to establish a system of 'scientific' boundaries, they expanded the Empire to the banks of Rhine, Danube, and Euphrates, but no further.9 The fortifications they constructed there were intended to accommodate a flexible and pre- emptive – as opposed to static – yet essentially defensive strategy. In Luttwak's system, these great rivers acted as definitive boundaries, and rationally so.10 Luttwak's work was criticized by historians on nearly all fronts, however. The very idea of a 'grand strategy' behind the wars and policies of the various emperors quickly fell out of favor, especially after an innovative study by Claude Nicolet in 1991, which demonstrated that the Romans did not possess the accurate geographic knowledge to implement any rational geopolitical strategy in the modern sense of the term.11 More importantly for the purposes of this thesis, though, his assertion that rivers were rational boundaries was firmly rejected. In 1987, V.A. Maxfield stated categorically that rivers are in fact “militarily weak”. Instead of operating as a natural line of defence or separation, they act as links between peoples on both sides: “they are highways which unite, not barriers which divide.”12 This maxim has taken on an almost canonical status in the historiography on the subject. Not the least among those who followed it was C.R. Whittaker, whose work in the 1990's essentially established the current consensus.13 In his model, the great northern rivers were not truly 6 Formulated most definitively by Whittaker (1994, 2004), see below. 7 For a recent example of this analysis of the sources, see Campbell (2012), p 53, 63, 98-99. 8 See note 7, above. At other times Campbell is almost entirely in agreement with my argument, although he fails to draw clear conclusions in response to the debate. See Campbell (2012), p 186-199. 9 Luttwak (1976), p 60. 10 Luttwak (1976), p 78. 11 Nicolet (1991). See for example Whittaker (1994), p 66-67. 12 Maxfield (1987), cited in Rankov (2005), p 175. 13 Whittaker (1994). See also Whittaker (2004). He was not alone, of course, and earlier works had contributed to this 5 boundaries at all; instead they were only a part of a broader ‘frontier zone’ that stretched well beyond the rivers themselves. Whittaker agrees with Maxfield, then, that rivers do not separate peoples, but bring them together. Moreover, in the military sphere they disappoint and cannot be held a defensive line – although, as Rankov points out, 14 he offers little in the way of evidence for this statement – and the legionary camps and other fortifications along their banks were intended not to defend the Empire’s borders from invasion, but to protect the river itself as a logistical asset. In Whittaker’s model, then, rivers were by no means useless in the grand scheme of things, but they were not boundaries; any indication to that purport in the sources reflects little more than convenience, and should not be taken too seriously. It is against this broadly shared understanding of the river frontiers of the Roman Empire, then, that Rankov rebelled. He explains that the difficulty of crossing a river is often underestimated – in fact, it is no easy task to, especially with a large and cumbersome army. Swimming is certainly not an option while carrying heavy weapons and armour, and to bring the whole army across on boats takes a long time, rendering it vulnerable to attack. The only viable option is to build a bridge across the river. This was a task at which the Romans were adept, but their enemies in the north less so. If the bridges were tightly controlled, then – and Rankov cites a number of sources demonstrating Roman caution in this regard – rivers could function quite effectively as military boundaries.15 To Rankov, Roman authors like Tacitus, asserting that the Empire was “enclosed by rivers” should be taken quite seriously after all. Although this all sounds very reasonable to me, and I am generally in agreement with Rankov, I am, like most historians, not a strategist or a military expert. Rankov and I draw the same conclusions, but in different ways – I have no real basis to support one appraisal of the defensive value of rivers over another.