1 Introduction
The visual military signalling employed in the Roman Empire was usually quite simple. The army did not have a professional signalling corps, and basic pre-arranged signals appear to be the extent of what was usually performed. In Byzantium, military signalling has a reputation of being more sophisticated. This is largely due to a famous 9th century long-distance optical telegraph which ran from Loulon on the Cilician frontier between Byzantium and the Abbasid Caliphate and Constantinople.1,2 This sophisticated optical telegraph appears to be sui generis, and references to optical communication in Byzantium are otherwise similar to what can be seen in Graeco-Roman antiquity. Military manuals and occasional other references to beacon communications tend to refer to simple, pre-arranged signals.3 This has not stopped scholars in looking for other beacon chains, however. Some of these are more or less plausible, such as a 6th century series of fortifications with a chain of intervisibility along the Via Axia in Macedonia, or on the islands of Euboia and Kalymnos.4 Others require
2 Background
Italy was ruled by the Ostrogothic kingdom after the end of the western Roman Empire. The entire peninsula was recaptured by the Romans in the middle of the 6th century, but military unrest in the A.D. 560s eventually coalesced into several Langobard polities.7 Constantinople retained control over the south as well as Liguria, Naples, and a corridor of land connecting Rome and Ravenna, the latter of which was the capital.8 In A.D. 751 the Langobardi conquered Ravenna and central Italy was lost to the empire. By the middle of the 9th century Arabs and Langobardi had taken most of Apulia from Byzantium, but a successful intervention under the emperor Basil I (r. A.D. 867–86) re-asserted authority in the region and Bari was retaken in A.D. 876.9 By the middle of
Leo of Ostia, the 11th century chronicler and monk of Montecassino, recorded that the military authority in Byzantine southern Italy, the katepano Basil Boioannes (A.D. 1017–28) fortified Troia, Dragonara, Civitate, and Fiorentino.13 By the mid-11th century all four were episcopal sees, which may date from the time of foundation, an were also an attempt to stamp Byzantine control on the landscape.14 Nearby Bovino and Lucera were already fortified.15 In addition, William of Apulia implies that Boioannes had done major construction work in Melfi.16 These locales named in the written texts form a chain running north-south along the (modern) north-western border that Apulia shares with Molise and Campania. In addition, Castelluccio Valmaggiore and Biccari have surviving Byzantine towers from the 11th century and Tertiveri, Biccari, and Montecorvino may have been new foundations at this time as well.17 Bari had
3 Methods
The technique employed here to examine visibility is the viewshed, a GIS (Geographic Information System) method to determine what points are visible from a given observation spot. Viewsheds are a blunt instrument and as such are best applied fairly generally, but serve a purpose here since the goal is to determine approximate point-to-point intervisibility.21 In addition, viewsheds permit a level of simulation that cannot be achieved by observation on the ground by accounting for the height of the viewer and the viewed point. While some Byzantine fortifications survive in Capitanata, most do not, thus making it difficult to make personal observations from an offset of 15 m above the ground, for example.
The total study area is approximately 10,500 square kilometres, comprising most of Foggia province in northern Puglia. Geodesic viewsheds were
The precise location and height of built structures are only estimates, and this also assumes that a structure is operating as part of an optical communication system. While a surviving tower may provide an obvious vantage point for visibility it may have been intended to serve other purposes such as defence, storage, or a way for an authority to stamp their mark on the landscape. An example of this is Castelluccio Valmaggiore, which has limited visibility despite a surviving tower of 20 m and being situated at a higher elevation than most of the other sites. Optical communication systems thus may have been based in the surroundings of a settlement and are not necessarily easy to detect archaeologically. A good example of this comes from the Byzantine city of Euchaïta in north-central Asia Minor. Field surveys have indicated that the city had a range of outposts in its immediate hinterland, some of which
4 Results and Discussion
The immediate question is whether the four new settlements founded by Basil Boioannes operated as an optical communication system. Civitate, Fiorentino, and Dragonara form a triangle in northern Capitanata; at no point is one of the new settlements more than 15 km from the others, whereas Troia is further to the south, about 28 km from Fiorentino. Both Dragonara and Civitate are adjacent to the northern frontier of Capitanata, as defined by the river Fortore.
The results of the viewsheds raise questions about the efficacy of such an optical telegraph (Figure 8.1). The first issue is that Dragonara, the fortification closest to the frontier, is also the lowest. At 68 m above sea level (aSL), it is far below Civitate (160 m aSL), and a similar problem exists in relation to Fiorentino (190 m aSL), and Troia (450 m aSL). The fluvial valleys of the Tavoliere mean that these places cannot see Dragonara, and the situation is also true in reverse: Dragonara cannot see Fiorentino, Civitate, or Troia. Dragonara commands views of the river Fortore and seems unlikely to have been part of an optical telegraph itself. This does not mean that the fortress could not have been in optical communication with some of the other new foundations. For example, the small hills west-south-west of Civitate could have served as an effective relay point. Similarly, the hills to the south and the east of Dragonara block views coming from Fiorentino. These are approximately 1 km from the main site and thus could easily be bridged by a relay, which need not have been optical. Work done on the Roman defences at Porolissum in modern Romania suggest that under good conditions auditory signals remain
Viewshed from the site of Dragonara (base data, Tarquini et al., 2012)
ILLUSTRATION: LUCAS MCMAHON
This is similar to Civitate, which can see the riverbanks but not the Fortore itself. Further north, Ripalta has good views over the opposing bank for approximately 12 km, as well as downstream as far as the Adriatic. A cumulative viewshed of the three locales (Figure 8.2) shows little overlap; the three sites can cover the river valley, but all three are necessary to encompass its length.27 The greatest overlap is on the left bank of the Fortore opposite Dragonara, but this area is more than 10 km out from Civitate and thus was less effectively under surveillance given the degradation of human vision over distance.28 Only tiny portions of prominent peaks are visible to all three, including Monterotaro. It seems too much of a coincidence that the three known Byzantine settlements of the 11th century together are able to see almost the entire course of the lower Fortore river valley, which attests to their role in border observation as well as the careful planning that went into the new sites. Their roughly equal spacing reinforces their defensive role: as the crow flies 13 km separate Ripalta and Civitate, and 12 km between Civitate and Dragonara. Even if these foundations were not able to communicate optically without the assistance of relays, news from one could be passed on to the others within a matter of hours by terrestrial means.
Multi-point viewshed from Dragonara, Civitate, and Ripalta (base data, Tarquini et al., 2012)
ILLUSTRATION: LUCAS MCMAHON
What about the fourth foundation of Boioannes, Troia? Located on an interfluvial spur 28 km south of Fiorentino, Troia was highly visible to its surroundings and consequently had extensive views (Figure 8.3). Perhaps more significantly, it was located on the Via Traiana, a 2nd century road that went from Benevento to Brindisi. The Via Traiana remained one of the major routes from central Italy to the southern Adriatic coast in the Middle Ages.30 Troia guarded the approach to Byzantine Italy from Benevento, and soon proved its worth when it stopped the army of the king of East Francia, Henry II, during his expedition to the south in A.D. 1022.31 Troia’s viewshed is excellent and extends further than 50 km in all directions except the west. Troia can see Civitate and Fiorentino. However, these do not establish a chain since Fiorentino cannot see Civitate. In any case, existing establishments need to be considered, and Lucera sits between Troia and Fiorentino. Lucera may have been part of the original re-conquest in the late 9th century and had been lost, but by the late 10th century was certainly part of the empire again.32 It would serve as an effective relay point, and is able to see Civitate, Fiorentino, and Troia, as well as the hills to the south and east of Dragonara.
Viewshed from Troia (base data, Tarquini et al., 2012)
ILLUSTRATION: LUCAS MCMAHON
The viewsheds of the new foundations are notably extensive in relation to the older chain of Byzantine defences to the south. Bovino, Sant’Agata di Puglia, and Melfi all have limited views, indicating that they were intended to control the landscape rather than observe vast expanses of it. Likewise, they are not easy to see and do not seem to have been able to communicate optically with each other. Ascoli Satriano functioned here in a way similar to Lucera or Troia, with much wider views despite being on lower ground, while being
This amount of intervisibility in Capitanata (Figure 8.4) creates a problem: if an optical signal is supposed to travel from one location to another to deliver
Multi-point viewshed and site-to site visibility of all sites named in the map in Byzantine northern Capitanata (base data Tarquini et al., 2012)
ILLUSTRATION: LUCAS MCMAHON
The transition from signal to message is where the drawbacks of optical signalling become evident. An optical signal that the enemy has been sighted only works if someone is on guard to light the first signal, and someone else is paying attention to receive it. The 12th century Greek romance Digenis Akritis has just such a case: the beacon is lit to summon soldiers, but no one shows up.33 In addition, the receiving party has to know what the signal means before it can become a message. The Strategikon, a late 6th century military manual ascribed to the emperor Maurikios, makes reference to signals having to be arranged in advance.34 Byzantium’s information-gathering efforts beyond its borders suggest that competent local administrators might have known when to be watching, although none of this is direct evidence for that.35
In that sense, the optical communication system is little more than a tripwire. The efforts of Leon the Mathematician in the 9th century to devise an optical telegraph that could send different messages is indicative of an awareness of this fundamental limitation. The surviving list of messages is, however, not encouraging. The four that are preserved mention enemy action, a raid, arson, or “something else” (ἄλλο τι).36 Such a message provides little in the way of useful military information, and nothing suggests that the 9th century beacon system was ever employed in other times or places. The size, composition, and bearing of an attacker is the sort of information that Byzantine military authorities were interested in: the Strategikon of Maurikios notes that experienced scouts should be able to estimate the size of an enemy force by looking at the ground trampled and the size of the camp, as well as by counting the
Despite these limitations, optical signals were clearly employed in the Byzantine world. However, the places where optical signalling is most prevalent outside of the realm of metaphor is in regard to military operations, particularly military treatises and historical texts that recount campaigns. Most of this signalling is short-range and impermanent, in that it takes place between units on the march, scouting parties, and small garrisons.42 Moreover, evidence from the Abbasid Caliphate points to the establishment of temporary communication infrastructure set up for a campaign season or two.43 Yet GIS visibility studies of the sort conducted above attempt to look at military communications from the perspective of permanent structures and static figures
5 Concluding Thoughts (I): Defensive Systems?
An invented scenario can put this all into perspective. Let us assume that the local garrison commander at Dragonara had received intelligence indicating that a Norman raid was being put together and had soldiers watching out. A dust cloud and flashes of metal indicated its imminent arrival, and lookouts in Dragonara saw this from some 6–7 km away.44 The Normans had to cross the Fortore, and even mounted were at least an hour from Dragonara. Dragonara dispatched riders to both Civitate and Fiorentino, both of which would ideally arrive in about an hour. This process is repeated, and by the end of the second hour Ripalta and Lucera have received the news. At this point the raiders will likely have reached Dragonara, forcing them to make a decision about whether to attack or to leave a garrisoned strongpoint to their rear. By the end of the third hour, the riders will have reached Tertiveri and Vaccarizza, each another 13 km from Lucera. From Tertiveri another 13 km will put a rider at Troia and thus on the main highway to Bari. From Troia the Via Traiana extends for 135 km to Bari, which would take the hypothetical rider a little more than two days to reach. That rider would arrive with militarily useful information, but this would ultimately take something like three days, at which point a decision would have to be made, messages sent, forces raised, etc., all the while a fast messenger was still two to three days from returning to Troia. Even if a local signalling system existed in northern Capitanata, its benefits would primarily be limited to the north. In terms of bringing information to the central authorities in Bari, a signal flashed from the Fortore frontier would reach Troia only 4–5 hours faster than a rider. Even the 9th century beacon chain was set up on the principle of more information over speed. While the system is noted for the arrival of the message within one hour of dispatch, the synchronization of the clocks meant that the outgoing message could be delayed by up to 23 hours. Thus, it seems unlikely that any optical system in northern Capitanata was in place for long-distance communications. Short-range signalling remains more likely, although the lack of site-to-site intervisibility without the inclusion of
6 Concluding Thoughts (II): Making Empire Visible in Capitanata
The practical efficacy of the intervention of Basil Boioannes for the defence of northern Capitanata is unclear. Troia resisted the East Frankish king and emperor. The Normans, who would bring Byzantine rule in southern Italy to an end, bypassed the system entirely, taking Melfi in early A.D. 1041, and Byzantine control seems to have been weak to non-existent by A.D. 1053 when the Normans decisively defeated a major combined papal-East Frankish force near Civitate.46 Intervisibility continued outside of times of war. The example of Lucera indicates that existing settlements came to be administered in a fashion more akin to other parts of the empire during the 11th century.47 The new settlements were set within a Byzantine administrative framework immediately upon foundation, as is suggested by the increasing employment of Byzantine titles and in archaeological evidence, such as the praitorion at Vaccarizza.48 However, top-down efforts to regularize the administration do not exclude local ethnic, religious, linguistic, and cultural variety. Ethnonyms found in Capitanata include Franks, Langobardi, Rus’, and Armenians, as well as Jews and people hailing from particular military districts in Byzantine Anatolia.49 New settlements meant the transplantation of peoples from elsewhere in the empire, and those people could retain memories of their origins
In a similar way, Dimitris Krallis argued that the imperial presence visible on a range of hilltops may have been intended to contribute to a sense of communal identity.53 In the case of 9th century Anatolia, the beacons linked province and capital and contributed to the idea that the capital shared in the threat posed by Arab raiders. While what sort of imagined community such intervisibility may have helped create remains a matter of informed speculation,54 the possibility of viewing (or being viewed by) multiple imperial fortresses from almost any point in northern Capitanata reinforced control over the landscape. Worth noting is how little the outermost defences can see beyond imperial lands to the west (Figure 8.5). Further investigation would be needed to establish the Byzantine character of these locales and their role in the local landscape, the view of an earlier outer line of defences in higher places combined with an inner line established by Boioannes is quite convincing from a cartographical perspective. Castelluccio Valmaggiore and Bovino have some control over their local valleys, their visibility towards the west is limited to a few kilometres. The more prominent Monterotaro and Montecorvino similarly
Cumulative viewshed from the westernmost sites (Bovino, Castelluccio Valmaggiore, Biccari, Montecorvino, and Monterotaro) (basedata Tarquini et al., 2012)
ILLUSTRATION: LUCAS MCMAHON
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Pattenden, “The Byzantine early warning system,” p. 259; McMahon, “Signaling empire,” p. 221.
Maurikios, Strategikon, 2.20, 9.5, pp. 140–42 and 330.
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Syrianos Magister, Peri strategias, 8, p. 26.
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Maurikios, Strategikon, 7.B.15, p. 258; Leon VI, Taktika 14.98, ed. and trans. George T. Dennis (Washington, D.C.: Dumbarton Oaks, 2010), pp. 344–46.
Syrianos Magister, Peri strategias, 8, p. 26.
Loud, The age of Robert Guiscard, pp. 92–101 and 118–20.
von Falkenhausen, “Zur byzantinischen Verwaltung Luceras,” pp. 395–401.
Vera von Falkenhausen, “Die Capitanata in byzantinischer Zeit,” Quellen und Forschungen aus italienischen Archiven und Bibliotheken 96 (2016), pp. 52–60; Cirelli, Lo Mele, and Noyé, “Vaccarizza: una cittadella,” pp. 7–8.
Annales Barenses, ed. W.J. Churchill (Toronto, 1979), pp. 119–20; Vera von Falkenhausen, “The Jews in Byzantine southern Italy,” in Jews in Byzantium: dialectics of minority and majority cultures, eds. Robert Bonfil, Oded Irshai, Guy Stroumsa and Rina Talgam (Leiden: Brill, 2012), pp. 281–94; Matheou, “Hegemony, elitedom, and ethnicity,” pp. 245–72.
Timothy Greenwood, “Basil I, Constantine VII and Armenian literary tradition in Byzantium,” in Reading in the Byzantine Empire and beyond, eds. Teresa Shawcross and Ida Toth (Cambridge: Cambridge University Press, 2018), pp. 447–66.
Annick Peters-Custot, “Between Rome and Constantinople: The Romanness of Byzantine southern Italy (9th–11th centuries),” in Transformations of Romanness, ed. Walter Pohl, Clemens Gantner, Cinzia Grifoni and Marianne Pollheimer-Mohaupt (Berlin: De Gruyter, 2018), pp. 231–40.
Syllabus Graecarum membranarum, pp. 18–20.
Dimitris Krallis, “Time, space, and physical reality: Byzantine authors and the materiality of the Roman imagined community,” in Byzantine authors and their times, ed. Vassiliki N. Vlyssidou, (Athens: NHRF, 2021), pp. 189–90.
Ruth M. van Dyke, R. Kyle Bocinsky, Thomas C. Windes and Tucker J. Robinson, “Great houses, shrines, and high places: intervisibility in the Chacoan world,” American Antiquity 81, no. 2 (2016), pp. 205–30.
James C. Scott, Against the grain: a deep history of the earliest states (New Haven, CT: Yale University Press, 2017), pp. 27–30.