and Vandal alliances, not least the Burgundians and Ostrogoths, to end
up on western Roman soil as well.
The overall threat to imperial survival posed by these unsubdued im-
migrants was straightforward. The Roman state funded its armies and
other state activities overwhelmingly from a land tax on agricultural
production. When the newly enlarged barbarian coalitions formed on
Roman territory and proved impossible to dismantle, they ate away at
this tax base by seizing control of provinces, with or without imperial
consent. The Visigoths, for instance, were originally settled in limited
areas of southern Gaul (as were the Burgundians) with imperial con-
sent, while the Vandals seized the richest provinces of North Africa
by force. These annexed areas then paid nothing further into imperial
coffers. At the same time, imperial consent to these settlements was
always extracted at sword point, which meant that substantial tracts of
the land that did remain in imperial hands suffered considerable dam-
age and were consequently much less able to pay their customary tax
dues. Emperors customarily seemed to have granted damaged areas
a tax remission of six-sevenths. Very quickly, therefore, these barbar-
ian settlements pushed the central authorities of the western imperial
state into a vicious cycle of decline. Losses of land and revenue un-
dermined the capacity of the state to maintain its armed forces and
hence its capacity to resist the further demands of barbarian intruders,
whether those already on Roman soil or new ones from outside. Even
the Visigoths, erstwhile imperial allies, were quick to take any oppor-
tunity to expand their own area of domination, notably under Euric,
who launched wars of conquest after 468 that brought most of Spain
and much of Gaul under Gothic rule. As this process worked itself out,
both Romans and barbarians eventually came to realize that the central
Roman state was no longer the major player in the politics of Western
Europe, and it is no accident that the final act of imperial dissolution,
240 Heather
the deposition of the last western emperor Romulus Augustulus, oc-
curred when the wage bill of the remaining Roman army of Italy could
no longer be paid.36
The relevance of this story to the modern world turns immediately
on the process of imperial collapse. The developed Western world has
a marked tendency to see strategic problems in terms of its own poli-
cies, of what it has or has not done or might do in the future, as if other
parties to any relationship do not have a say in the ultimate train of
events. A similar kind of attitude is apparent in traditional approaches
to Roman imperial collapse, which largely focus on whether Roman
frontier strategies were wise enough or sufficient to combat the out-
side threat. An overall picture of developing patterns of political, social,
and economic organization in Central Europe of the Roman period,
however, emphasizes that it is just as important to focus on what the
so-called barbarians were doing. So often historians, usually following
Roman commentators themselves, have discussed the ultimate fate of
the frontier in terms of whether Rome, at different points in its his-
tory, found or lost the magic strategic calculus, when in reality, given
developing conditions on the ground, the empire’s fate was substan-
tially contingent on what was happening across the frontier. Rome was
at heart a Mediterranean-based empire that used those resources to
exercise domination over large parts of more northerly Europe. The
ultimate reason why the empire fell, and why a Mediterranean-based
state has never been so dominant in Western Eurasian history since,
lies in the fact that the first millennium marks a crucial watershed in
the development of Europe as a whole. New farming techniques gen-
erated much larger populations, which were then mobilized by much
more sophisticated political structures. The result was a fundamental
shift in the strategic balance of power, which meant that Mediterra-
nean resources no longer provided a sufficient power base from which
to exercise European domination. The accident of Hunnic intrusion
may have dictated exactly how and when the empire fell, but it was the
unleashing of forces of development in barbarian Europe that meant
that it was bound to fall sometime, and, what’s more, never return.
Perhaps even more important, I suspect, is what this story has to tell
us about the dynamic forces unleashed when originally less-developed
Frontier Defense 241
economies and political structures come into contact—on a whole
series of levels—with larger-scale imperial neighbors. For much of
the transformation that generated larger and more powerful socio-
economic and political structures on the fringes of the Roman world
in the first half of the first millennium AD can be traced to the con-
sequences of unprecedented contacts between barbarian and imperial
Europe: military, economic, political, and indeed cultural. Again, this
is not just a story of the empire doing things but of barbarians react-
ing with intelligence and determination to the opportunities and dan-
gers that imperial policies presented. In fact, the development of the
Germanic world is only one example of a much more general phe-
nomenon. In response both to the positive opportunities such contacts
presented and to the negative factor of aggressive exploitation that em-
pires generally exercise over their originally weaker neighbors, such
societies often display a marked tendency to develop and reorganize
themselves in such a way as to overturn the original inequalities of
power. Highly analogous patterns of development, for instance, are
visible among Slavic societies on the fringes of Frankish imperial Eu-
rope in the second half of the millennium.37 And this pattern, I would
argue, has held good to a considerable extent in more modern contexts
too, where the developed West’s economic, political, and even military
domination, so evident across the globe in the twentieth century, is
rapidly being overturned by outside political structures—modern bar-
barians, if you will—that it previously exploited but that have taken full
advantage of its dangers and opportunities to reorganize themselves.
What all of these examples suggest to me, in short, is that there often
operates a kind of Newton’s Third Law of Empires. The exercise of im-
perial political dominance and economic exploitation will in the long
run stimulate a series of reactions that turns initially weaker neighbors
into societies much more capable of resisting or even overturning the
aggressive imperialism that set those reactions in train.
Further Reading
The most important single work on Roman frontier defense continues to be Edward N.
Luttwak, The Grand Strategy of the Roman Empire from the First Century a.d. to the Third
242 Heather
(Baltimore: Johns Hopkins University Press, 1976). Luttwak is not an ancient historian
but a strategic analy
st who applied his expertise to the archaeological evidence of
Roman frontier fortifications and troop deployments. His cogent analysis—suggest-
ing that the empire moved deliberately from attack to defense in depth at the end of
the second century AD—set the agenda for all subsequent work, even if its conclu-
sions have been substantially modified. Three works among other notable titles—J. C.
Mann, “Power, Force and the Frontiers of the Empire,” Journal of Roman Studies 69
(1979): 175–83, C. R. Whittaker, Frontiers of the Roman Empire: A Social and Economic Study
(Baltimore: Johns Hopkins University Press, 1994), and B. Isaac, The Limits of Empire:
The Roman Army in the East, 2nd rev. ed. (Oxford: Oxford University Press, 1993)—have
among them shown that internal political agendas often adversely affected the work-
ing of truly rational foreign policy, and that command and control limitations made it
extremely unlikely that emperors were capable of the kind of strategic overview that
Luttwak’s hypotheses require.
Whittaker’s work has also contributed to a second critique, along with sustained
archaeological investigations conveniently summarized in such studies as L. Hedeager,
“The Evolution of Germanic Society 1–400 AD,” in First Millennium Papers: Western Eu-
rope in the First Millennium, ed. R. F. Jones, J.H.F. Bloehmers, S. L. Dyson, and M. Biddle,
129–44, B.A.R. International Series 401 (Oxford, 1988), and Maureen Carroll, Romans,
Celts and Germans: The German Provinces of Rome (Stroud, UK, 2001). These works have
demonstrated the extent to which the world beyond the frontier was transformed by
sustained economic interaction with the empire. My own work, particularly “The Late
Roman Art of Client Management and the Grand Strategy Debate,” in The Transforma-
tion of Frontiers from Late Antiquity to the Carolingians: Proceedings of the Second Plenary
Conference, European Science Foundation Transformation of the Roman World Project, ed.
Walter Pohl, Ian N. Wood, and Helmut Reinitz, 15–68 (Leiden: Brill, 2000), has drawn
on historical evidence (little explored by Luttwak) to show both that Rome did not in
fact move onto the defensive, as he supposed, and that Roman military and diplomatic
activities, in conjunction with economic interactions, played a major role in creating
larger and more coherent political structures in neighboring barbarian societies. For
the argument that it was this transformation of the north and east that eventually
made it impossible for a Mediterranean-based state to extend a Europe-wide domina-
tion, see now Peter J. Heather, Empires and Barbarians: Migration, Development and the
Creation of Europe (London: Macmillan, 2009).
Notes
1 Edward N. Luttwak, The Grand Strategy of the Roman Empire from the First Century
a.d. to the Third (Baltimore: Johns Hopkins University Press, 1976).
2 Ammianus Marcellinus 28.5, with further comment in Peter J. Heather, The Fall of
the Roman Empire: A New History (London: Macmillan, 2005), 67–68.
3 Ammianus 28.2, 29.6; Themistius Orationes 10. These moments do show up in the
archaeology: James Lander, Roman Stone Fortifications from the First Century a.d. to the
Fourth, B.A.R International Series 206 (Oxford, 1984); Sandor Soproni, Der spätrömische
Frontier Defense 243
Limes zwischen Esztergom und Szentendre (Budapest: Akademiai Kiado, 1978); Constantin
Scorpan, Limes Scythiae: Topographical and Stratigraphical Research on the Late Roman For-
tifications on the Lower Danube, B.A.R. International Series 88 (Oxford, 1980).
4 Ammianus 26.5, 27.1.
5 John Drinkwater, The Alamanni and Rome 213–496 (Oxford: Oxford University Press,
2007), has recently argued that all Roman operations on the Upper Rhine frontier were
driven by different emperors’ needs for prestige rather than by military necessity, but
this is to overstate the point. True, the Alamanni did not by themselves (see below)
pose a threat to the overall existence of the empire, but they were responsible for sub-
stantial raiding (see note 20) and occasionally threatened local annexations of Roman
territory: in the 350s, for instance, a band some 50 km wide in the Rhine valley. For
more limited—and to my mind more convincing—general critiques of the “rational”
Luttwak approach, see J. C. Mann, “Power, Force and the Frontiers of the Empire,”
Journal of Roman Studies 69 (1979): 175–83; C. R. Whittaker, Frontiers of the Roman Empire:
A Social and Economic Study (Baltimore: Johns Hopkins University Press, 1994).
6 Mann, “Power, Force”; see esp. Benjamin H. Isaac, The Limits of Empire: The Roman
Army in the East, 2nd rev. ed. (Oxford: Oxford University Press, 1993), ix. For further
comment, see Heather, Fall of the Roman Empire, chap. 2.
7 L. Michael Whitby, Rome at War ad 293–696 (Oxford: Oxford University Press, 2002),
provides an excellent introduction to issues of readiness and mobility; see now John F.
Matthews, The Journey of Theophanes: Travel, Business, and Daily Life in the Roman East
(New Haven, CT: Yale University Press, 2006), on the limited speeds possible even for
officially assisted travelers.
8 Tetrarchic campaigns have to be reconstructed largely from very fragmented
narrative sources and the evidence of the victory titles they claimed: see Timothy D.
Barnes, The New Empire of Diocletian and Constantine (Cambridge, MA: Harvard Univer-
sity Press, 1982). The main sources for the mid-fourth century are the first part of the
Anonymous Valesianus and then the full and contemporary narrative of Ammianus
Marcellinus for the years 354–78. General commentary and more detailed discussion
of the pattern can be found in Peter J. Heather, “The Late Roman Art of Client Man-
agement and the Grand Strategy Debate,” in The Transformation of Frontiers from Late
Antiquity to the Carolingians: Proceedings of the Second Plenary Conference, European Science Foundation Transformation of the Roman World Project, ed. Walter Pohl, Ian N. Wood, and
Helmut Reinitz, 15–68 (Leiden: Brill, 2000).
9 Compare, e.g., the Caesar Julian on the Rhine frontier and the Augustus Constantius
on the Middle Danube, both in the 350s: Ammianus 17.1, 6, 10, 18.2 (Julian); 17.12–13 (Con-
stantius). But the pattern was the same with Valentinian on the Rhine in the 360s and 370s
(Ammianus 27.2, 10, 29.4) and Valens on the Lower Danube in the 360s (Ammianus 27.5).
10 Maureen Carroll, Romans, Celts and Germans: The German Provinces of Rome
(Stroud, UK, 2001) is excellent on the economically debilitating effects of constant im-
perial campaigning on Germanic groups of the Weser in the first and second centuries.
Drinkwater, Alamanni, 9, shows that the Alamannia exhibited marked signs of eco-
nomic development in the fifth century after Roman raiding stopped.
11 Maximian: Panegyrici Latini 2 [10].7–10. Julian: Ammianus 17.1.12–13, 17.10, 18.2.15–
19. Constantius: Ammianus 17.12.9–21.
244 Heather
12 See further discussion in Heather, “Client Management.”
13 Ammianus 17.12.9ff. On subsidies, see further Heather, “Client Management,” and
on the longer-term history, Johannes Klose, Roms Klientel-Randstaaten am Rhein und an
der Donau: Beitrage zu ihrer Geschichte und rechtlichen Stellung im 1. und 2. J
hdt. N. Chr.
(Breslau: Marcus, 1934).
14 Some examples of forced drafts of manpower: Ammianus 17.13.3, 28.5.4, 30.6.1,
31.10.17.
15 Panegyrici Latini 7 [6].10.1–7; see Ammianus 27.2.9 for another example from 366.
16 E.g., Ammianus 17.1.12–13, 10.8–9, 18.2.19.
17 Limigantes: Ammianus 17.13. The Tetrarchs organized substantial resettlements,
particularly of Franks and Carpi; see Erich Zollner, Geschichte der Franken bis zur Mitte
des sechsten Jahrhunderts (Munich: Beck, 1970), and Gh. Bichir, The Archaeology and His-
tory of the Carpi, trans. Nubar Hampartumian, B.A.R. Supplementary Series 16 (Oxford,
1976). Constantine resettled more Sarmatians in the empire in the 330s: Anonymous Vae-
sianus 6.32. On the terms of such settlements, see Peter J. Heather, Goths and Romans
332–489 (Oxford, 1991), 4. For all the precautions, resettlement could occasionally go
badly wrong: Ammianus 19.11.
18 Detailed report: Die Alamannenbeute aus dem Rhein bei Neupotz, ed. Ernst Küunzl,
4 vols. (Mainz: Verlag des Römisch-Germanischen Zentralmuseums, 1993). A brief
English summary can be found in K. Painter, “Booty from a Roman Villa Found in the
Rhine,” Minerva 5 (1994): 22–27.
19 Heather, Goths and Romans, 3. E. A. Thompson, The Early Germans (Oxford: Oxford
University Press, 1965), shows how rare such an economically open frontier arrange-
ment was.
20 On the execution of hostages, note the laments of the Alamanni recorded at Am-
mianus 28.2.8–9. David C. Braund, Rome and the Friendly King: The Character of Client
Kingship (London: Macmillan, 1984), explores Roman cultural diplomacy more gener-
ally. Not that it always worked. The Gothic royal hostage taken by Constantine in 332
seems to have reacted adversely to the experience, advising his son to have nothing
to do with the Romans: Ammianus 27.5.9, with Herwig Wolfram, History of the Goths
(Berkeley and Los Angeles: University of California Press, 1988), 62ff. On the other
hand, Ammianus received help from an ex-hostage who had come to love classical
learning when on a spying mission on the Persian front: Ammianus 18.6.17ff.
21 Macrianus: Ammianus 29.4.2–5; Vadomarius: Ammianus 21.4.1–6 (see also 21.3.5;
26.8.2); Vithicabius: Ammianus 27.10.3–4; Gabinus: Ammianus 29.6.3–5; leadership of
Gothic Tervingi: Ammianus 31.5.5–8.
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