In general terms, it seems that the East Roman or Byzantine state up to the end of the twelfth century evolved a number of variants on a system of defence in depth. But all the variations were the result of the interplay between three fundamental features of the political and social-economic situation of the Byzantine world: first, the resources that were available to the government for the training, equipping and maintenance of armies, and the ways through which those resources could be appropriated and redistributed; second, the international political context, and especially the level of political organization and ideological sophistication—“statehood”—attained by the empire’s neighbours; third, the technological/organizational sophistication of its enemies.
The late Roman system, grounded in a division between mobile field forces and less mobile (but not entirely static) defensive garrisons both along and well behind the frontier regions, was orientated entirely towards defence, although the field forces could be mobilized for occasional counterstrikes into enemy territory. Longer-term offensive operations normally involved taking considerable bodies of troops away from other regions, thus weakening their defences and making attacks on those areas more attractive, as Justinian’s offensives in the west demonstrate. This system had evolved from the third century, through several permutations, primarily to withstand the pressures of large numbers of small attacks along the frontiers with occasionally much larger invading armies pushing deeper into Roman territory. The Romans—and their medieval successors—certainly had a clear notion of a linear frontier or border, both in respect of political demarcation and in terms of cultural differentiation. But such linear distinctions had little or no military relevance and were of only limited strategic value. On the contrary, frontier zones were established in which local garrisons based in fortified centres could respond to local attacks either by meeting them in the field and driving them off, or retiring into their bases and sallying out to harass and hinder enemy movement, deprive them of supplies and generally make the raid unviable and unprofitable as quickly as possible. The same system was intended to deal with challenges of a more serious nature, whether better organized or simply larger in numbers. Defensive strategy permitted the invaders to penetrate the frontier, but then ensured that they had to confront a series of “hard points”, major fortified centres or military garrisons. If these were attacked, the enemy’s resources and lines of communication became vulnerable as time and energy were expended in trying to capture them; if they were avoided, the soldiers based there could sally out to harass the enemy column or columns, preventing them from collecting forage and supplies, limiting their freedom of movement and so forth. At the same time, this allowed time for other mobile forces to concentrate and march to meet the enemy in battle. Warfare then became a war of manoeuvre and attrition, as the enemy force attempted to avoid contact and escape with its booty, and as Roman commanders attempted either to surround the enemy and overwhelm his forces numerically before attacking, or alternatively, and in order to avoid a full-scale battle, to persuade him to withdraw quickly due to lack of resources.
The technological-organizational advantage held by the Romans in the Balkans generally meant that this strategy worked reasonably well at the first level until the later sixth century: barbarian forces were generally after shortterm gains in booty and slaves. In fact, archaeological evidence suggests that this system never worked quite like this, and that from the beginning defence in depth involved a much more differentiated pattern of settlement and distribution of military resources than the written record might suggest. Against the Persians, technologically the equals of the Roman forces and able to conduct successful long-term siege warfare, Roman defences generally operated at the second level: small-scale raids did occur (from both Persians and from Arab raiders), but major attacks deep into Roman territory were well planned and had a specific purpose (to extract tribute and booty) as well as a longer-term political-strategic aim. Occasionally the “hard points” were taken, but for the most part the Roman defensive system worked reasonably well, certainly if judged by the continued political and territorial integrity of the empire.59
In the late sixth and early seventh centuries, however, the system was seriously compromised on both fronts, as we have seen. Maurice’s aggressive offensive against the Avars in the Balkans appear to have been remarkably successful, but its longer-term implications remain unknown, since the coup d’etat in which he perished meant the return to a more passive defensive strategy and the continued infiltration of Roman territory by Slav immigrants. By the middle of the seventh century the Romans could control some of the
Danube and the Danube delta, the Aegean coastlands to a point, but hardly any of the interior away from major fortified settlements and arterial routes. In the east, initial Persian successes were facilitated by the disaffection of substantial elements of the eastern field armies, allowing the Sassanian commanders to deal with each army group on a piecemeal basis and roll up the defensive system in Syria and then Palestine before turning their attention to Egypt and Anatolia. Heraclius’ defeat of the Persians enabled him to start rebuilding the old system with a certain degree of success, but the Arab invasions effectively put an end to this process and totally altered the strategic geography of the Middle and Near East in the process.
The new strategic system which evolved out of this situation was even more clearly defensively orientated, although from an institutional perspective it grew organically out of the late Roman arrangements. Three defensive zones gradually evolved—an outer band of territories subject to regular raiding and devastation based around a series of hard points, fortresses and forts which frequently changed hands but which always had to be dealt with before any longer-term penetration of Byzantine territory could be contemplated; an inner belt of territories in which the forces most regularly employed to respond to enemy attacks were based, again focused on a series of more heavily defended foci which served also as fiscal and military administrative centres; and a third core zone which was the object of enemy attacks on occasion, which was also organized along the same lines as the second zone, but which also provided the resources for the maintenance of the imperial capital and government and its field armies, a last line of defence before the walls of the city itself. This was a highly flexible system which could tolerate extreme pressure in terms of economic damage and demographic dislocation—as in the invasion and occupation of some of the core zone in the years 674—8 and 717—18, for example—but which, by adopting a strategy of avoidance and harassment for its armies, reliance upon the survival of major fortified centres and dispersal of resources, made a knock-out blow extremely difficult, and rendered a full-scale occupation and pacification of the provinces simply too costly a proposition.
Yet such a defensive option was clearly often—indeed, frequently—exercised to the detriment of the population of regions most exposed to hostile activity. In Asia Minor the empire relied heavily upon a network of frontier outposts and forts covering major routes and passes and other strategic locations, well fortified or well concealed refuges to which the local populace could flee when warned of an impending attack, and provincial armies which were organized at a local level to harass and hinder enemy movements rather than to confront and defeat their armies. Although large Arab armies sometimes did successfully invest and capture major fortified centres, this was—in proportion to the much larger number of simple booty-collecting raids or attacks intended to seek out and destroy Byzantine armies—comparatively infrequent. The Byzantine policy of simply avoiding confrontation and holding out until the enemy forces were compelled to retire, in spite of the considerable costs borne by the provincials in the most exposed areas, seems to have been effective enough to discourage successful permanent penetration of the frontier regions and ensure the state’s continued ability to extract resources sufficient to maintain its apparatus.60 In the Balkans, a less defensive system was operated. Given the less sophisticated logistical arrangements of its enemies and greater Byzantine efficiency and flexibility in tactical organization, the empire could rely upon a military standoff, moderated by diplomatic activity, to maintain a degree of equilibrium, although frequent raids deep into imperial territory, and vice versa, raids intended to reinforce political demands rather than ideological claims, gave warfare in this theatre some of the characteristics of warfare in Asia Minor.
Two aspects may be worth highlighting at this point. The first is that there is virtually no evidence for the Byzantine government or individual military commanders ever having attempted to establish a “hard” frontier, in the sense represented by, for example, the artificial linear defensive structures typified by Hadrian’s wall in North Britain. There are some minor and short-lived exceptions, but the generalization appears valid throughout the period in question. The corollary of this is that, in the second place, the alternative “soft” or permeable defensive arrangements were not simply a response to lack of resources, or the appropriate technology, or the overwhelming advantage which the enemies of the empire sometimes possessed in respect of manpower and related logistical matters. A “soft” defence was not merely a reflection of circumstances.
In the Balkans the late Roman state—in the form of the provincial and military administration—appears to have recognized the development of a greater diversity of fortified settlement types, as a direct response to the nature of hostile activity and its effects on the economies of the provinces concerned, reflecting the need to protect the provincial populations from the implications of a permeable frontier. Even this arrangement succumbed to the pressure on resources and the nature of the trans-Danubian immigration from the later sixth century. Yet there is some evidence to suggest that the methods which had been evolved in the Balkans may then have been pursued somewhat more deliberately and even systematically in the Anatolian context during the second half of the seventh century, so that the system which evolved there was directly related to imperial experience in the Balkans.61 The rate at which this occurred remains to be established; neither is it clear to what extent the evidence from inscriptions in the fortifications of a number of fortified sites in Asia Minor demonstrates the activity of the central government in this respect. A defensive strategy very similar to that which had evolved in the Balkans from the third century emerges in Anatolia from the middle and later seventh century, in an area where such a strategic infrastructure had been entirely unnecessary until the Persian invasions of the early seventh century
The chief characteristic of the Byzantine system was thus the permeable frontier. Not only are raiders or invading armies not halted at the “frontier”, they are not even brought to battle, except under the most favourable circumstances (or where a foolhardy commander risks a battle). Instead, conflict is avoided wherever possible (conserving limited manpower), and the populations of the countryside and their moveable possessions and livestock brought into places of security (conserving limited resources). Ensconced in their fortresses and strongholds or mountain refuges, the army and the civil population wait until the enemy have had enough and go away. This usually occurred after a relatively short time, since larger forces were subject to the dangers of disease as well as problems of water supply and fodder, while substantial amounts of booty made withdrawal slower and more subject to ambush and counter-attack. Such a strategy was only one side of an imperial response to its defensive needs, of course. For the role of diplomacy was absolutely crucial in complementing this military activity: fomenting discontent among enemy troops or leaders, delaying negotiations until the enemy armies ran out of supplies or were assailed by disease, persuading the enemy that relief forces were about to fall upon them or that their homeland had been attacked by imperial allies, these and a host of other methods were employed in a sophisticated armoury of non-military weapons at the disposal of an imperial government, and there can be little doubt that it was this combination which enabled the imperial government to survive so many apparently fatal onslaughts.62
During the period of military expansion and reconquest in the late tenth and early eleventh centuries, this system began to change. Instead of a defence in depth, a system of frontier districts based on one or more major fortified positions and their mobile garrisons was established. Outside this were in turn arranged a number of client emirates or states in the east, kept in check by occasional displays of imperial military force and by diplomatic efforts. In the west, a linear frontier with neighbouring states could be maintained by diplomatic means and through mutual economic arrangements. From the last quarter of the tenth century, the eastern end of the Danube was re-established as a semi-permeable frontier, a frontier that was extended westwards after Basil II’s destruction of the second Bulgarian empire. Archaeological evidence for the systematic reoccupation or reconstruction of a number of late Roman installations in this region and the dating of this work suggests that this was associated with the perceived threat from the Rus’ after their defeat at imperial hands in the early 970s. There is little evidence that this policy was maintained under Basil II, however, and its abandonment is probably to be connected with the assumed disappearance of the threat after the alliance made between Byzantium and Kiev in the late 980s. Nevertheless, the Danube and its associated river systems in the northwest Balkan region did function as a frontier between the empire and its northern neighbours, especially the kingdom of Hungary, during the twelfth century, although the sources suggest that it was guarded by a skeleton force of watchposts and forts at key crossing places, as well as a frontier hinterland zone which was deliberately kept depopulated to discourage raiding. Indeed, the evidence demonstrates that the disposition of imperial forces from the early eleventh to the end of the twelfth century in the Balkans was directed as much at internal security as at external pressures, which were contained by a combination of diplomatic activity and occasional demonstrations of imperial military power.63
The international context had changed sufficiently by this period to negate some of the advantages held by the East Roman state in the sixth and seventh centuries. If we exclude the nomadic peoples of the steppe, most of the peoples neighbouring the empire—whether potential enemies or friends—had evolved more complex state forms, including the administrative and logistical arrangements necessary to put substantial and well-armed forces into the field, even if only on a short-term seasonal basis. This had always been the case in the east, of course, even in the time of the early caliphate, but not in the west. In addition, the tactical advantage held by well-disciplined imperial armies over barbarian forces had been in most cases equalized by developments in heavy cavalry warfare and siege technology by the eleventh and certainly by the twelfth centuries. If the emperors of the seventh and eighth centuries could treat most of their enemies as barbarians, those of the tenth and eleventh, and more particularly the emperors of the twelfth century, had to recognize that they were, for the most part, dealing with peoples or states who were no longer their organizational and logistical inferiors. Strategy had to respond to this changed context.
The system of the later tenth and early eleventh centuries evolved as a preclusive defence—reflecting a political-military context in which incursions into imperial territory were rare, while permitting imperial field forces to reinforce diplomacy on the territory of the empire’s neighbours or enemies. As long as enemies appeared infrequently, or singly, on one front at a time, and in an international political context where the empire’s military standing would generally discourage territorial incursions, this was sufficient; and these appear to have been the assumptions made by emperors and their advisors in the period c. 1025—59. But it was inflexible when confronted by a multiplicity of threats, because the underlying lack of resources did not permit any sudden expansion of armed forces necessary adequately to combat such challenges. The sudden increase in military pressure on the empire in the middle and later eleventh century, combined with internal factionalism and diversion of military resources away from the external threat, was too much for this revised system, and it began to break down, with the results that will be discussed in Chapter 3. In addition, and especially significant from the overall strategic perspective, the failure of the empire to maintain an effective warfleet through the later eleventh and especially the later twelfth centuries meant that terrestrial strategic dispositions could always be—and sometimes were—outflanked by maritime forces. The events of 1203—4 made the point disastrously clearly.
Paradoxically, the principles, although not the form, of the defensive system in Anatolia after the recovery under Alexios I Komnenos were at base the same as those which had prevailed in the eighth and early ninth centuries. In the Balkans, in contrast, the Komnenoi made an effort to re-establish and maintain the principle of a linear frontier, although a defence-in-depth element was also recognized and taken into account. But the fiscal costs to the population, and the political dangers inherent in extracting the necessary resources in regions which were already culturally disaffected, were enormous. The structural tensions within this system, in the Balkans in particular, become obvious when, following the Fourth Crusade, the territories of the empire dissolved into a series of regional powers, to a greater or lesser degree reflecting ethnic, cultural and religious lines of difference.
World History
