Τὰ δὲ φρούρια ἐξηύρηται πρῶτον μὲν κατασκοπῆς ἕνεκα τῆς τῶν ἐχθρῶν παρουσίας, δεύτερον δὲ διὰ τὴν τῶν αὐτομόλων ὑποδοχήν, τρίτον διὰ τὸ κατέχειν τοὺς ἡμετέρους φυγάδας, καὶ τέταρτον διὰ τὸ ἀθρόον ἐμπίπτειν ἡμᾶς τοῖς τὰ ἄκρα οἰκοῦσι τῶν πολεμίων, οὐ μᾶλλον λείας ἕνεκα ἤ ἀνακρίσεως τῶν παρὰ τοῖς ἐχθροῖς τελουμένων καὶ περὶ ὧν ἄν αὐτοὶ καθ' ἡμῶν βουλεύονται.
Δεῖ δὲ τὰ φρούρια πλησίον ποιεῖν τῶν ὅρων καὶ μὴ πόρρω ἀφεστηκότα τῶν ἐχθρῶν τῆς παρόδου.....
Ανώνυμος, Περί Στρατηγίας.
Fortresses are independent defensive structures with a military purpose, established at key strategic locations. They are descended from the Roman battle camps, the castra and the smaller castellum, which are divided again into improvised and semi-permanent or permanent examples. They are walled, rectangular in plan, with a moat and with towers at the corners and sides. Built first in wood, they were gradually converted into stone. Starting in the 4th century, fortresses were moved up from the plains onto the naturally fortified terrain of hills. Since the time of Julian the habit was observed of positioning forts in restricted places to control passes.
The zone of safety that the presence of a fortress created for the area surrounding it from very early on encouraged the creation of settlements around them. This phenomenon has been observed earlier: the Roman camps built on the plains gradually evolved into fortress-towns – a process which continued in the 4th century, and intensified in the 6th.
The medieval forts adopted irregular shapes that depended on the topography of the area; they abandoned the rigid symmetry that distinguishes the earlier Roman ones. Following the system of defence in depth by creating successive defensive lines, these forts often contained a citadel with a central tower-donjon serving as the last point of resistance. This tower was the seat of the local lord, officer or deputy in charge of the garrison, while in the Frankish period it also acted as the residence of the feudal lord.
A concern for symmetry returned to fortress design at the time of Venetian and Ottoman rule. The type of fortress developed to address the powerful artillery in existence by the mid 15th century followed a new defensive system: the bastion (fronte bastionato) which was established in the 16th century. Typically the design, now a specialized branch of architecture, has a fortress of polygonal ground plan, with pentagonal bastions at the corners, linked by straight walls (curtain walls), all surrounded by a moat.
The Citadel (or Acropolis), the highest and most strongly fortified point of a town or a fortification system, has been a key point in defence since prehistory. Inaccessible terrain and the presence of a perennial water-supply are essential criteria for choosing a position for a citadel.
In the city-state created during Antiquity the citadel (aka city) on top of a hill formed the central focus for a fairly wide area (i.e. the countryside). It acted not only as a refuge for the surrounding rural settlements, but also as a religious and political centre. During the Classical and Hellenistic times, the citadel became reserved for holy matters; whilst the area around it became urbanized and protected by an enclosing wall. This concept of the citadel was not continued in the Roman period, as the Romans developed a different military approach, that of attack over defence; but it was revived in the hard times of Late Antiquity. In the Byzantine era, citadels usually had a central tower (donjon). Such strong towers were indeed known in the Hellenistic and Roman times, where they were incorporated as elements of the defensive wall. Under the Franks, they became independent structures.
The citadel as a fortification type spread throughout the Byzantine territory in the 11th and 12th centuries: sometimes they existed independently of the settlement, and sometimes are enclosed within it. In addition, they were often administrative centres and the seat of the Bishop. During the late 13th and the 14th centuries the citadel further housed the residence of the local feudal lord or ruler, symbolizing their power. In this way, the owner of the castle was not only protected from a potential external enemy, but also from the unpredictable mob of his subjects that at times could prove dangerous too.
The fortified city.
Since antiquity, a city tended to grow up near or around a citadel, which was its religious and administrative centre. It was often protected by a fortified wall. During the Roman era, some camps built in valleys evolved into fortresses-towns, but the non-walled cities remained the prevalent form under the pax romana. The barbarian threat, combined with both socioeconomic and administrative circumstances in play in the 3rd century onwards, led to the need for the reconstruction of the large earlier-built fortifications and the creation of new ones. As a result, the small towns declined, and the population increased in the large urban centres, while in the ancient metropoleis only the urban core was fortified. These established cities (as centres of trade) differ from the settlements now established in naturally fortified positions: they were larger in size with administrative, commercial and financial capacities. During the Middle Byzantine period, economic growth and political stability were conducive to the strengthening of cities, both those surviving from antiquity, and those created during the previous centuries.
As for the arrangement and ordering of the fortifications, the following alternatives are distinguishable: a) fortified citadel surrounded by unwalled city, b) fortified citadel surrounded by walled city, c) walled citadel independent of the walled city below it. In walled Early and Middle Byzantine citadels the existence of a powerful tower (keep-donjon) is typical: this forms the seat for the local lord, officer or deputy.
The emergence of a large number of fortified settlements (smaller units than the cities, often by quite a margin) is particularly to be observed during the Early Byzantine years. The socio-political changes and the barbarian risk which grew in strength in the 4th century and lasted to the 6th resulted in the abandonment of the small towns in the empire, their immuration and the concentration of population in the large ancient cities, and especially the creation of small fortified settlements. These last differ from the cities proper in their usually small size, but also by their lack both of a strong trading and economic structure and of administrative functions.
This situation arose from the relocation away from the Roman forts on the plains to the more inaccessible heights, a process in motion since the 3rd century. This migration involved new settlement patterns too: the resulting communities are called oppida and oppidula for the smaller ones. These forts acquired an irregular shape, dependant on the topography of the steep hill: an element that differentiates them from the many small towns built throughout the empire a little earlier, during the Tetrarchy. With the emergence of these small fortified settlements on hills, the empire took on a more rural cast. The city-castles that came into being took on administrative bent, which could be lost in the revival of some major cities during the Middle Byzantine period.
The fortified settlement has a citadel that serves as the ultimate refuge in a time of siege. From the 6th century on within the citadel walls there often appears a strong tower (keep-donjon). The presence of this tower dominates the scene in the following centuries.
Such were more or less straight walls running between two natural end-points. They were designed to prevent passage. As such they formed the first line of defence and the means of intercepting an enemy. Such structures are generally to be found at an isthmus, or some such narrowing of the way. Usually the choice of location and construction of such projects indicates state planning, as in the case of those in Thrace attributed to Anastasios or the Hexamilion Wall in the area of Corinth. These structures could also form part of an aqueduct-system, e.g. the Anastasoupoleos-Peritheorion and the Christoupoleos.
This type of fortification project made an equal use of earthen mounds, which are one of the earliest approaches to fortification in human history. Their timeless functionality is evident from their employment in periods of quite different dates: such as the Tetrarchy, the Byzantine, but also the Venetian, as the embankment behind the walls in the area of Lechaio makes plain.
The tower is a key defensive element: it may either be linked to a broader defensive system as seen in the fortification of settlements and towns, fortresses and citadels, or it may stand alone. The latter sort of tower functioned already in the Classical era as a lookout-point in a control-system, but also as a fryktoria, through which visual contact was possible with similar structures in a network, which made possible the transfer of important messages.
In the Middle Ages, the tower was equally the core around which a small settlement grew and a refuge in a period of siege. Also, the tower had a role in monastic complexes, sometimes as part of the fortification and sometimes by itself to control and protect agricultural production. Many examples survive from the 10th to the 14th centuries, mainly in the monasteries of Mount Athos. During the Late Byzantine era, with the increased insecurity, towers grew more common in the landscape and acquired a new function besides that of the purely military, namely that of residence. The development of such use is reflected in the post-Byzantine tower-house (see below).
As for the arrangement of the tower, the walls were without projections or had buttresses, as mainly seen in northern Greece. The quadrangular tower usually had more than one storey. The divisions between them are either by means of wood floors resting on cross-beams or on vaults built on arches. Where part of a monastery, the upper floor was often formed into a chapel. The internal configuration of a tower mainly had one big room per floor. On the ground floor there were no openings, for security reasons; there is usually a cistern here. Access to the main entrance, located on the first floor, was by means of a retractable wooden ladder; as normally was any communication between levels. In the lower floors arrow-slits existed with windows in the upper floors. From machicolations on the roof defenders could throw stones and other available materials down onto their enemies, while simultaneously unleashing their fire from behind the ramparts. The tower was protected in most cases by a precinct or enceinte wall.
An independent tower is to be found within the citadel, especially in the Frankish period. This powerful tower (keep-donjon), besides being the place for the last-stand in a siege, acted as the residence of the feudal lord. The existence of the central tower is continued in Ottoman fortification practices.
The defensive potential of the tower is the main reason for its use as a house even before the turbulent Late Byzantine years. The establishment of this practice came about from the type of house which had an adjoining tower. Gradually, the tower itself was transformed into a fortified residence: accordingly also known as the tower-house.
The tower-house retained all the defensive elements and layout of the towers-proper, as seen in the Byzantine castles and monasteries: such as being rectangular in plan, of more than one storey, with the main entrance on the first floor, and wooden stairs and trap-doors to gain access to other storeys, machicolations on the roof and above the main entrance, the lack of openings on the lower levels, the arrow-slits and the flat roof with battlements. As an extra defensive element bartizans were added at the corners.
The towers were either rectangular in plan; or T-shaped, where a rectangular element is added across one side of a small rectangular space; or finally, L-shaped (kastrokatoikies) with the entrance placed in the inner angle for its better defence from the sides. The withdrawable ladder that allows access to the main entrance was in later examples replaced by a stone staircase. On the ground floor there was a vaulted cistern and a pantry. Some earlier examples possessed vaulted ceilings and roof. The floors are wooden. Next to the tower there were often other subsidiary outbuildings.
The towers ensured the safety of their owners from piratical raids or local uprisings, while at the same time were directly involved with the farming of the surrounding area. They therefore are mainly to be found in the countryside. Later, such could be simply a holiday-home for the wealthier people: their possession always strengthened the social standing of their owners.
In the Peloponnese the number of towers is very high in the post-Byzantine period and especially during the Second period of Ottoman rule (1715-1821). This is due to the general insecurity prevailing until the extermination of the remaining thieves was achieved in the first decade of the 19th century, as well as being felt by the wealthier of the conquerors who were living amidst the beggared subdued. These constructions belonged mainly to Turkish officials, or Greek notables; and after 1715 to Albanians as well.
The tower-house from the 18th century evolved in response to the social and economic conditions in play in each region, but despite the new elements that came into being, such as the oblong shape, the larger and wider openings in the walls, it yet kept unaltered some of its defensive features.
Elements of defence
Οἰκονόμησον τὰ τείχη τὰ διερρωγότα, τοὺς πύργους τοὺς προμαχῶνας κατοχύρωσον, σώρευσον λίθους ἐπάνωθεν τῶν τειχέων, πλέξον λέσας, ποίησον χάντακας διπλοῦς καὶ τριπλοῦς καὶ βαθυτάτους καὶ πλατεῖς...
The component elements of any fortification function as reciprocating measures of protection and defence. They may be divided into the passive sort – capable of resisting enemy attacks, and the active – for launching forays and aggressively repelling an enemy. This last is achieved by the defenders unleashing fire on the foe from as many directions as possible: such defensive fire is delivered either vertically (i.e. from above) or laterally (from the side, aka enfilading).
Accordingly, the requirements for an active or passive role in a fortification will define its character: whether it acts simply as a refuge or as a base for operations.
Components of an active defensive system
Battlements: These served to enable vertical fire down on the enemy: they consisted of the solid sections (merlons) and gaps between (crenels). The first provided cover for the defenders; they alternated with gaps (variously-shaped loopholes and embrasures), running along the upper edge of the walls. In case of attack the gaps could be closed by wooden shutters, swivelling on a horizontal axis to open or shut them. The merlons could be straight sided and flat-topped, or triangular in form. From the 14th century on, in the castles or fortifications of the Knights Hospitaller, the top was usually notched (V-shaped), creating a swallowtail effect.
Allure or Walkway: The corridor designed for the ease of movement for the defending soldiers, set right behind the battlements, whence they directed their fire. The feature was over time improved by the introduction of two firing steps instead of one.
Tower: Sideways or enfilading fire can only be unleashed from positions that project forward of the enceinte wall: such are designed to protect and clear the part of the fortifications adjacent to them from the enemies’ presence. The origins of such planning in Greece appear in Mycenaean fortification, although they do not yet have towers, being formed so that they can protect the gates. The incorporation of the tower in the enceinte wall to permit enfilading fire is noted in the late Archaic and Classical periods (7th-5th centuries). From the 4th century onwards, the use of new methods of siege warfare were very widespread and intensive, and the importance that enfilading fire acquired was comparably great.
The towers built during the Archaic and Classical period are usually of a square ground plan. Those with a rounded wall-plan were constructed when the use of siege rams and catapults spread. These semicircular towers are considered to have originally been developed and introduced from Mesopotamia and the Middle East in general. The Romans used mainly U-shaped towers. Triangular versions probably appeared in the 3rd-4th centuries, with their use spreading widely in the 5th and 6th centuries. Pentagonal towers belong more to fortifications of the late 5th and 6th centuries. The five-sided form, with a forward projecting angle (aka pentagonal, prow-shaped) so typical of Hellenistic fortifications, returned to favour after the 5th century, and became a norm in the Byzantine period. Several examples and types of such a tower are to be found in Greece, Asia Minor and the Balkans: they influenced western attitudes too but without dominating them. This tower-type survived into early Venetian fortifications and developed into the bastion with a curved outline that continued in use in fortifications right down to the 17th century.
Projection: They are triangular protrusions set in the wall to enable enfilading fire. This defensive element serves as a simpler version of a tower, which it replaced when the needs of economy in materials and costs were paramount.
Bastion: A military consequence developed from the need for protection as the new way of war, involving firearms, was established in the 15th century. This is a compact open ‘square’ (piazza), which is set forward from the general fortification line to protect the same by allowing enfilading fire of artillery and weaponry placed on the bastion.
The bastion, which is protected by a moat, consists of two faces (faccie/fronti) and two sides (fianchi), while the fifth side at the rear of the unit, the neck (gola), is left open. The sides of the bastion thus merge into the curtain walls (cortine). On the sides of the bastion were at first formed low platforms for the placement of gun-batteries; later on these are transferred to the inside and were protected by the angular shape of the flank of the bastion (spalla). Sometimes, the bastion could be totally independent from the rest of the defensive structure.
Machicolations: Such were intended to direct vertical fire down onto an enemy. They are stone-built projecting chambers, with no floor, from which the defenders, leaning outwards within the protective box, unleashed their attack. Though their assault is commonly said to be accomplished by boiling oil or water, it has been argued it was stones that were mostly thrown, because of the lack of availability of the other materials or the high cost of acquiring them. These projections were placed at key points in the walls – above entrances, and were supported on corbels, arches and buttresses.
Wooden platforms or hoardings cantilevered out (hourds), stone machicolations, and brattices (bretèches or machicoulis) all appear during the Roman era or early medieval period, and were much in use until the 15th century AD. The machicolations were introduced in the Greek regions during the 13th century by the Franks, who seem to have borrowed them in turn from the Islamic fortification tradition. Such projections enabling the throwing of various materials from openings in the floor are to be found in Islamic palaces in the late 8th century.
Murder-holes: Vertical fire can be unleashed on the heads of the enemy from these. They are openings left in the top of the arch of a vaulted passageway, the through-corridor, which normally is attached to the main castle-gate. From these openings, the defenders threw stones and any other material available to them if the foe managed to break through the main gate.
Arrow-loops/slits: This is a vertical slot from which it was possible to aim a long-bow or a crossbow. Within the thickness of the wall, the exterior narrow slit widens to the interior so that the archer may position himself best to make the desired shot. The shape of these gradually changed with the intention of providing a better coverage and wider filed of fire. Early arrow-slits are a narrow slit or a rectangular opening with solid one-piece jambs and lintels of stone. However, in the Middle Byzantine period the system of using a different masonry for the jambs was abandoned, and the lintels were made of wood. Sometimes the lintel may have an arched shape. Blind arches appear on the facades of arrow-slits from the 12th century onwards. Arrow-slits appear in castles built by the Franks.
Cannon embrasures: With the introduction of firearms in the 15th century, there were opened wider gaps in the thick screen provided by the walls and parapets: usually trapezoidal in plan, they were for the placement of cannons.
Gun-loops/slits: This was a vertical slot (as it appeared from the outside), which expanded inside the thickness of the wall to the interior, where the defender stood to fire his small-arms. They essentially serve the same purpose and work in the same way as the later version of the arrow-slits.
Postern gate: A secondary and small gate that could be used for a surprise attack against enemies, especially during a siege. Sallies were a common practice designed to harass the besiegers, without compromising the defensive capability of the fortifications. Through such sudden raids the defenders could steal or destroy siege equipment, food and other supplies from the enemy, as well as whittle down their numbers.
Bartizans: These are chambers, usually circular, that project out (especially at the corners and on the sides) from the upper-storeys of the tower-houses of the post-Byzantine times. In the exterior wall there were opened slits by which the tower could be defended using small-arms. The floor too could be supplied with similar for the same purpose: thus both vertical and enfilading fire was possible.
Components of an passive defensive system
Outwork: An independent wall, less high than the enclosure wall it is set in front of. It provides the first line of defence: its presence protects the lower part of the enceinte walls from the fire of the attackers and their tunnelling.
Moat: An artificial barrier that acts as the first line to intercept an enemy. It is a perimeter ditch which protected the fortifications on their outside. Moats have appeared in front of fortifications since the Neolithic period, but they became an indispensable element of defence in the 4th century BC to prevent siege engines approaching the walls. As siege engines evolved, so the use of moats increased. From the Middle Ages it is certain that they could be filled with water too. The device was equally well adapted to the post-Byzantine fortification system relying on bastions.
Raisable bridges (drawbridge): Frequently in medieval fortifications this sort of moveable bridge was located in front of the main gate of the castle, lying above the moat. In an emergency, the bridge is lifted, thereby cutting off access to the interior of the castle. This feature is also seen in domestic architecture. The retractable stairs/ladders served the same purpose in the Late Byzantine towers, which also acted as homes; later in the post-Byzantine tower-houses was created the lifting or retractable wooden bridge, paired with an independent staircase.
Gateway: This is the communication means for those within the castle to get to the area outside the walls; in the case of an urban fortification system it was the connection point between the main country roads with those inside the walled city. As one of the most vulnerable points in a fortification, particular attention was given to its defence. The main gate is often protected by two towers flanking it: a pattern occurring since antiquity. The defensive capacity of the main gate can be increased by adding a portcullis, by having a succession of gates and by equipping the passageway with murder-holes and firing-slits.
Portcullis: A wooden, metal-clad grille protecting the door-leaves. The portcullis was set within vertical grooves in the side-jambs and in front of the gate: it was raised or dropped by means of a counterweight or screw positioned in a space above the gate.
Precinct or Enceinte Wall: As early as the Neolithic period, the precinct wall was the primary means of protection for a settlement. The early enclosures lacked towers; their integration in the walls is a feature of the late Archaic and Classical periods (7th-5th centuries). Usually the spaces between the towers range from 30 to 70 meters.
Batter (scarpa): This is the inclined portion found at the base of the wall, seen in western castles already in the medieval period: its purpose is to make difficult any possible approach to the walls by some machine of war. Following the introduction of firearms in the 15th century, this shaping of the wall was retained, now more to impede the creation of tunnels beneath the wall foundations, and to deflect projectiles from artillery. The batter was covered by carefully laid masonry on the outside; inside its filling was of rubble. The decorative horizontal cordon (cordone) delineated the top of the batter, above which rose the vertical face of the wall.
Contrama: Vaulted corridor behind the scarpa/batter, running the entire length of the wall. The purpose of the tunnel is so that any undermining of the walls by the enemy cannot go undetected by the defenders.
Screen: The high breastwork (parapetto) comprising the upper part of the wall used after the introduction of firearms and onwards. It is very very thick; into it were set openings (embrasures), usually trapezoidal in shape, for the mounting of cannons.
Citadel: This is a walled enclosure that serves as the last point of defence. Usually, it has an independent defensive capacity. In the Late Byzantine era, the citadel contains the central tower/keep, which is the place of residence of the local ruler or governor.
Central tower/keep or donjon: This tower, usually located at the highest point of the castle, is the ultimate Last Stand, to which the defenders resort when all else fails. The ground level was used as a storage area and/or cistern, while the upper storeys contained the reception hall and functioned as living quarters.
Look-out and Guard-post: A prominently-placed structure acting as a look-out point (Guardiola or Sentinella) very often to be seen in Venetian fortifications. Such devices are found in the Bourtzi, the Palamidi, and on Acronafplia.
Development of fortifications
Χωρία τοίνυν ἐπιτήδεια ἐστὶν εἰς κτίσιν πόλεως, καὶ μάλιστα εἰ μέλλοι πλησιαίτερα κεῖσθαι τῶν ὅρων, ὅσα κατὰ λόφων κεῖται, κρημνοὶ δὲ κύκλῳ τὴν ἄνοδον ἀποφράττουσιν, ἔτι δὲ καὶ ὅσα ὑπὸ μεγίστων ποταμῶν κυκλοῦται ἤ κυκλοῦσθαι δύναται οὐ δυναμένων ἄλλοθι μεταφέρεσθαι διὰ τὴν τοῦ χωρίου φύσιν, ἔτι δὲ καὶ ὅσα ἐπὶ θαλάττης ἤ μεγίστων ποταμῶν κείμενα ἰσθμῶν ἔχει θέσιν ὀλίγῳ παντελῶς μέρει τῇ ἠπείρῳ συναπτόμενα.
Ανώνυμος, Περί Στρατηγίας.
Prehistoric times. The concept of an enclosing wall that thereby protects the settlement within it already existed in the Neolithic era. These early precincts originally had no towers and were made up of small stones, in contrast to the megalithic fortifications of the Mycenaean citadels that came later. This early phase also saw the development of the first ditches or moats and of taller structures designed for refuge and observation.
Historical Antiquity. The addition for the first time of towers of rectangular plan is noted in the late Archaic and Classical periods (7th-5th centuries), with the objective of achieving enfilading fire. In the 5th century the heightening and strengthening of the walls was undertaken because of the now frequent use of catapults and siege towers of some stature, which were able to violently overwhelm the thin and medium-height walls in use until then. The employment of siege engines contributed equally to the fashioning of towers with curved walls (i.e. no corners) to give them greater strength. However, their high cost of manufacture prevented them from totally replacing the rectangular form. In the 4th century the first emphasis on the strategy of an active defence is made clear with the frequent presence of small gates (sally ports) in the enceinte wall, so the defenders could more readily surprise the enemy with sudden forays. It is even possible to find examples of walls with regular setbacks that allow covering and enfilading fire, and also the pentagonal tower with its angled and projecting front, as well as polygonal towers (square towers with apotetmimenes corners).
The Roman Empire. The conditions created by the victory of the Romans and the pax romana meant that big cities could remain without walls. The Romans were also more interested in the tactics of attack and therefore, rather than continuing the established practice of the single citadel as a place of refuge, preferred to create numerous camps, called castra (the smallest unit of these was the castellum). These fortifications consisted of a rectangular enclosure with a ditch and towers at the corners and along the sides. Gradually they developed into fortress-towns, built on the plains.
From the 3rd century onwards, however, the barbarian invasions, the collapse of existing institutions, a drop in population and other socio-political changes all led to the need both to build new fortifications and to repair and reinforce older ones. The ancient metropoleis still surviving were fortified by an enclosing wall, equipped with projecting rampart towers and an external moat or ditch. Only the urban core is so defended. At that time too the Roman forts were repositioned from the plains to more naturally fortified positions (i.e. on raised ground). This decision left room for a greater freedom in their design, as the placement of the towers needed to be at the most vulnerable and important points of the fortification, and not simply at regular intervals as before.
At the time of Tetrarchy (284-313) this policy of extending or reconstructing earlier fortifications continued. Further throughout the empire new and small fortified settlements were established. Simultaneously in cities with an imperial glamour attempts at monumentalization were undertaken - decorated facades and large towers were erected.
The Early Byzantine period. The transposition of both the small military outposts (castellum) and the larger forts (castrum) from the plains to naturally fortified hills was maintained during the period of Constantine the Great (324-337). In the 4th century strongholds were seen both as ways to bottle-up and so control passes and also as stand-alone rectangular towers (turris) that functioned primarily as look-out posts or for the transmission of messages.
From the late 4th to the 7th centuries the barbarian presence and changes that accordingly happened to the socio-economic structure of the empire caused the abandonment of small towns; the population moved into the medium and larger cities. The cities still surviving from antiquity shrank: only a small part of them was fortified any more, and usually hastily contrived, because of the risk of raids. The construction of fortresses on hills with an accompanying settlement becomes the norm. These settlements and forts had a citadel to protect the inhabitants of the surrounding area in any period of siege. Often its precinct had one tower stronger than others (aka the main tower-donjon-keep-refuge), which at the time was still constructed on the wall-line, but was structurally independent from it. This central tower commonly occurred from the 6th century onwards: it will be a feature of the Byzantine fortification system. The danger of barbarian raids also resulted in an increase in the number of towers in the courtyard space. Towers of the 5th and 6th centuries were rectangular in plan, also pentagonal with a point, circular, triangular and horseshoe-shaped. At the end of the period, as an additional line of defence, outworks were constructed, while the practice of partitioning within, that had survived from the Roman period, was revived.
Transitional times. The insecurity created by the invasions of the Slavs by land and the Arab presence on the sea led to further population movements and abandonments of territory. At that time the castle-building system of the early Middle Ages was devised. The role of the castles was strengthened through the creation of the administrative institution of the theme: the imperial power was now exercised through these units.
In the tactics of warfare, the positioning of the fort and the steep terrain are the most important defensive factors, since war machines can no longer reach them. A particular feature is the predominance of the pentagonal tower with its externally protruding point; its employment is general in the wars between the Byzantines and the Arabs (7th-10th centuries).
The Middle Byzantine period. The practice of siting fortified settlements on high ground was also followed in the Middle Byzantine period. The citadel tower by now had usually been separated from the rest of the village by a wall or was set independently of it nearby. At that time we can observe the expansion of cities beyond their original walls, thanks to the stable political conditions in the Middle Byzantine period that enabled their economic growth.
The defensive technology developed now is characterized by battlements of varying heights and arrow-slits of a small height and a narrow width – a fact that may suggest the use of the crossbow, especially at the time of Manuel Comnenus. If one compares the towers of the 5th century with the 12th century walls of Constantinople, then the Middle Byzantine walls are seen to be less carefully built, with much use of spolia, and their towers are lower, but more massive and set closer together.
After the Crusades. The new conquerors proceeded to reuse and reconstruct earlier fortifications, but also to build new ones, feudal in character: these last follow, as do the corresponding Palaiologan ones, the design principles of the early Middle Ages. Built on hilltops, mostly of irregular shape, they had both secondary enclosures surrounding the settlement and a citadel with a strong tower/keep.
However, these feudal strongholds differed from the earlier Byzantine fortifications in size. They were usually small and served as the seat of a lord or a garrison, unlike the Byzantine ones that usually involved towns that survived from antiquity. The feudal castles sported certain characteristics of the contemporary western approach to fortifications. One of these is in the function of the central tower, which now became physically independent as befitted the residence of the feudal lord and shelter for his family. All Western strongholds of the 13th century are constructed so that the buildings inside the citadel abutted the wall, forming an open central courtyard.
The castles of the period have high vertical walls with towers. The defenders first kept the enemy at a distance with arrows shot horizontally from the battlements; when he got near, they struck at him with more vertical bow-shots or repelled him by throwing from projecting devices (machicoulis) stones or other materials. The Byzantine habit of building towers with an open back spread to the Frankish fortifications, because of the low building-costs and the shorter time needed for construction.
Within this period of uncertainty, the need for defence was strong in the private sphere too. This is demonstrated by the construction of individual towers, with or without secondary auxiliary structures. These towers protect houses or religious complexes: they had few openings at the lower levels, but places whence to throw missiles existed on the roof and above the entrance, which was found on the first floor level. Often patterns in brick and monograms decorated their faces, especially from the mid-14th century onwards.
Ottomans and Venetians. In the mid-15th century occurred the most decisive development in the history of fortification: the introduction of firearms following the spread of gunpowder in the 14th century. This development resulted in the formation of a new defensive system, based on the bastion (fronte bastionato). This is a system of fortification essentially polygonal in plan, formed by five-sided bastions at its corners, which were joined by straight walls (cortine/curtain wall). Externally, the fort was protected by a moat. The development of this system was carried out in the first half of the 16th century, and fully established by the end of the same century: it was applied by the Venetians in strategic locations in order to protect their marine hegemony in the Mediterranean.
According to the principles of the system, the wall is of a low height and tripartite: a) scarpa (battered plinth, scarp) comprises the externally inclined section at the wall’s base - its application led to the abandonment of vertical fire. The considerable thickness that results increases the resistance of the wall to a missile strike, b) cordone (cordon, roll) is the semicircular and projecting horizontal band that separates the scarpa from the parapetto above, and c) parapetto (parapet) forms the top section of the wall that protects the fighters and through which openings for cannon are left. Strong platforms, the bastions proper, projected beyond the main wall-line of defence: thus enfilading fire could be achieved. The theoretical design of this new type of fortress goes back to a specialized sector of architectural practice, that in which mainly military engineers in the service of Venice specialized: for example, Antonio da Sangallo, Michele Sanmicheli, Giulio Savorgnano, Gian Girolamo Sanmicheli, Gabriele Tadino da Martinengo.
Until the mid-15th century, Venice worked only on the modernization of existing fortifications of the cities-commercial stations she occupied. Although the uneven terrain usually precluded the complete application of any theoretical design, the Venetians, however, lowered the earlier walls, strengthening them in thickness by adding a scarpa, while the battlements with arrow-slits gave way to the parapet with its cannon embrasures. As for the towers set in the fortification line, from the mid-15th up to the early 16th centuries the rectangular ones were replaced by massive round towers with enclosed spaces (casematte) for the mounting of cannons and sloping bases designed to increase resistance to the impact of projectiles. However, because of the smoke generated by firing, and also their limited field of fire, the cannons were quickly transported onto the roof of the towers or set in open squares. As a result there formed a projecting expanse of considerable size, which will go on to become the pentagonal bastion.
From the 16th and 17th centuries, Venice proceeded with the new approach to construction based on the bastion system, while equally adopting those solutions developed in contemporary western fortifications, such as the τανάλιας as seen at the Acronafplia in 1715.
As a result of the Venetian-Turkish wars, the Peloponnese was occupied also by the Ottoman Turks. Unlike the Venetians, the Ottomans did not prioritize the construction of new fortifications. The lack of interest was the result of the pax ottoman on the consolidation of the Ottoman Empire. The Ottomans carried out new construction only when the occasion demanded; basically they reconstructed or revamped any existing fortifications they chose to occupy. As to the main features of any fortification of theirs, in no particulars did they differ from that of a Venetian one. A special item added to the Ottoman defences is the construction of a large central tower, a reversion to the medieval tradition.
At the time of Venetian and Ottoman rule, a period of intense insecurity, the same defensive trends were observed equally in domestic structures, with the introduction of the tower-house.
The Years of Revolution. In the 19th century in Europe as a whole, the concept of fortification changed – with the intent of preventing the bombardment of cities by artillery with a much longer range of fire. Now was being developed more a concept of external enclosures, consisting of small strongholds-cum-artillery emplacements, independent of each other. Meanwhile, in Greece – in the context of the Liberation struggles – there were constructed stone embankments, redoubts known as ‘drums’, at several key strategic positions. Equally, earlier large-scale fortifications were re-used, and even individual towers could serve as bases for the rebels.
The feeling of insecurity and the need for protection prevailing once again in these difficult years was indicated by the large number of tower-houses built in the Peloponnese at the time, particularly between 1715 and 1821.