Читать книгу Military Architecture in England During the Middle Ages - A. Hamilton Thompson - Страница 6

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The history of military fortification in England begins with those strongholds which, at vast expense of labour, the early inhabitants of Britain hewed out of the soil, surrounding defensible positions with ramparts of earth, divided by deep fosses. The approximate date of these earthworks can be determined only by excavation, and a vast amount of work remains to be done in this direction. The number, however, of those which can be proved to be earlier than the Roman occupation is very large; and, of this number, a considerable portion, including some of the most stupendous examples of fortified hill-camps, may have been the work of neolithic man some two thousand years before the Christian era. Relative dates in this connection concern us less than principles of fortification. The hill-camps of pre-Roman Britain may be divided roughly into two classes. In the first place, there are those which occupy the summit of a promontory of high land, which slopes so steeply on all sides but one that artificial defence is necessary on that side alone. The second class is that of the so-called “contour forts,” in which the summit of a hill is utilised for the camp, and encircled by trenches following the contour of the ground.

Maiden Castle

In each case the defences provided by the inhabitants consist of earthen banks, the materials of which have been dug from the fosses or ditches which surround their outer face. An earthen bank and fosse, thrown across the neck of land between the promontory and the plateau beyond, convert the extremity of the promontory into a fortified enclosure. Well-known examples of such fortresses are the three camps, one on the east and two on the west side of the river, which guarded the valley of the Avon at Clifton. The labour necessary for the construction of these was naturally far less than that which went to the making of the great contour fortresses, of which so many splendid examples remain in Somerset, Wiltshire, Dorset, and in the chalk districts generally. In these cases, the whole area, or at any rate the greater part of it, stood in need of entrenchment. There are points at which the slope is so precipitous that the bank and ditch were dispensed with, or, as in part of Cissbury camp near Worthing, only a single bank or ditch was necessary.1 Also, the steeper the ground, the less was the labour required in constructing the entrenchments. But these positions often took the form of enclosures surrounded by double or triple lines of defence, often of stupendous size. For the greater part of its extent, the vallum or bank of the oval camp of Cissbury is double, and along the outer edge of the encircling fosse is a formidable counterscarp or parapet. Poundbury, which lies on the high ground west of Dorchester, has a single bank and ditch on its east and south sides. On the west side the bank is doubled; but the north side, where the hill falls almost perpendicularly to the Frome, was left without artificial defence. The superb fortress of Maiden Castle (2), which crowns an isolated hill, 432 feet high, south of Dorchester, shows a bewildering complication of plan. The oval central space is ringed by a number of banks and ditches, which varies from three on the north side to as many as eight about the western entrance.

Maiden Castle; plan

These early camps form merely the preface to our subject, and attention need be called only to some general features. Their character, like that of the medieval town or castle, was strictly defensive. They were the strongholds of races whose weapons were of a very primitive description, and could carry to no great range. What their inhabitants needed was an impregnable fortress, within which they and their herds could be well sheltered from attack. They belong to a day before siege operations were possible. To carry them, a determined onset and a hand-to-hand fight were necessary. Their strength therefore depended on the complexity of their defences. No enemy could hope to scale the flanking banks of Maiden Castle, one by one. The entrances to the camp, at its eastern and western ends (3), were so elaborately concealed by the overlapping ramparts, that even on a ground-plan they are far from obvious; and it was almost inevitable that an attacking force, without a guide acquainted with the ground, would be decoyed into a cul-de-sac and overwhelmed by the missiles of the defenders on the ramparts.

Old Sarum

(From Mr Hadrian Allcroft’s Earthwork of England by kind permission of Messrs Macmillan & Co.)

The steepness of the bank itself constituted a formidable means of defence. At Maiden Castle the great northern banks rise to a height of 60 feet or more. The top of the outer bank of Old Sarum (4) is 106 feet above the level of the ditch below.2 In many cases, and probably in all, the inner bank was crowned by a stockade, consisting of a series of upright stakes, between and round which was twined an impenetrable hedge of thorns. The plateau or berm which was sometimes left behind the parapet of the bank, where there was more than a single bank and ditch, was a valuable asset to the defenders of prehistoric strongholds, forming an advance post from which they were able to wield their missiles freely; while sometimes the summit of one or more of the outer banks was made for the same purpose into a broad platform, which allowed greater freedom of movement. The parapet or counterscarp of the outer ditch was probably defended by a stockade, and it is known that in some cases sharpened stakes or stones were fixed firmly in the bottom of the ditches.

Bury Ditches

The impregnable character of the enceinte was thus ensured. But further skill was necessary to defend the entrances of the camp. Of these there was usually more than one, and these were necessarily formed by cuttings through the banks. As in the case of Maiden Castle, the path of entry could be converted into a labyrinth by multiplying the banks and ditches. Every inch of this circuitous path is guarded by tall ramparts: there are seven or eight points in its course at which fatal error was possible, and one at any rate where an attacking army could hardly fail to rush securely upon destruction. The eastern entrance is so guarded by transverse banks that the path is almost equally difficult to find. It was seldom, however, that entrances were so elaborately protected. At Old Sarum the western entrance is covered by a semicircular outwork, on the flanks of which are the two inlets to the passage through the outer vallum. On the east side the entrance is through a narrow passage which runs for some distance between the parapet of the outer ditch and an outwork, and is at right angles to the actual passage through the bank. The most common method of defending the entrance was to make a diagonal path, usually from right to left, through the banks. Each bank would thus overlap the next: the summits above the path would be broadened out into platforms, capable of occupation by bodies of defenders; and the right flank of the enemy, unprotected by shields, would be exposed to their missiles. The entrance, however, might be substantially protected by giving an inward curve to the inner bank on each side of the path; and this is a plan very frequently employed.3 Where outworks were specially constructed, their form differs considerably: we have seen them employed in two ways at Old Sarum—as a kind of horn-work thrown out in front of a passage, and as a spur projecting at right angles in front of an entrance. In both cases an absolutely straight approach is precluded. Occasionally, where an approximately direct approach was permitted, it is guarded on one side by a spur thrown out at right angles to the bank. At Blackbury castle, an early earthwork in south Devon, the main entrance has a straight approach guarded on either side by a triangular outwork, which is formed by a most ingenious arrangement of banks and by prolongations of the main ditch (7). At the actual entrance the main bank is curved outwards, with broad platforms at the top. The hollow interiors of the outworks might serve as guard-houses, or the attacking force could be driven into them from the gateway of the fort, and penned in a position from which escape was impossible. Sometimes hollows were made in the bank or in a projecting outwork near the gateway to serve as guard-houses. On either side of the main entrance, the bank was often slightly raised. At least one instance is known in which the main gate was concealed by making a break in another part of the rampart, and raising the bank on either side. The enemy, making for this point, would miss the real entrance, and run the risk of losing his life in a cul-de-sac purposely constructed within the rampart.

Blackbury Castle

(From Mr Hadrian Allcroft’s Earthwork of England by kind permission of Messrs Macmillan & Co.)

In these fortresses, the defences of which were due to instinctive skill in the face of constant danger, it is impossible not to recognise how many of the most scientific features of medieval fortification were anticipated. The concentric plan of Caerphilly castle (270), with its easy provisions of egress, and its difficulty of access; the spurs which guard the approaches to Beaumaris (277) and Conway castles; the barbicans which form so prominent a defence of Alnwick castle (243), and the gateways of York have prototypes, of which their engineers were probably unconscious, in the huge earthworks of prehistoric Britain. Through a long interval, in which military art pursued a very gradual evolution, the wheel came full circle. The devices of the earthwork builders were translated into stone with far greater economy of labour.

Although the most conspicuous examples of early earthwork are found in hill fortresses, camps were not confined to hilly sites, nor were their defences always composed of earthwork. There are districts where the hard nature of the soil forbade the construction of earthen banks and fosses; and consequently there are many camps which are surrounded by walls of rough uncemented stone, originally kept in place by facings and bondings of larger and smoother stones.4 These camps are usually not large. They occur very commonly in the north of England: a good example is that known as the Castles, in the valley of the Bedburn, seven or eight miles west of Bishop Auckland. The enclosure, situated on a boggy slope, is surrounded by shapeless masses of débris, the ruins of the dry-built ring wall, which has lost its facing and so has fallen to pieces. Stone was also used in the ramparts of some of the camps on the rocky hills of Somerset, as in the camps on either side of the Avon at Clifton. The great fortress of Worlebury, above Weston-super-Mare, was surrounded by an immense wall of uncemented stone, brought to great thickness by building several walls, each with its own set of facing stones, up against each other. On its eastern front, separated from the main rampart by a deep ditch, cut in the solid rock, was another wall of stone; and this again was protected by a series of outer earthworks (9). Dolebury, at the western extremity of the Mendips, is surrounded by a double wall of loose limestone.5 In these cases, as in the Welsh strongholds of Penmaenmawr and Tre’r Ceiri, geological conditions made the earthen bank an impossibility, and the stone of the neighbourhood took its place.

Worlebury

(From Mr Hadrian Allcroft’s Earthwork of England, by kind permission of Messrs Macmillan & Co.)

It has often been argued that these prehistoric fortresses were merely places of refuge, to which, in time of war, the dwellers in the levels below betook themselves and their flocks. But it is much more probable that they were the permanent habitations of communities, not merely camps, but fixed settlements, chosen for habitation on account of their strong position, and gradually fortified by labour which may have been the work, in the more elaborate examples, of many generations. The need of permanent protection for themselves and their flocks and herds seems to have been felt by the early inhabitants of Britain to such an extent that their regular settlements naturally took the semblance of fortified camps. This is very evident in the case of those camps which are found in positions where the natural advantages are very small—positions which might be chosen by people in search of an abode, but would hardly be chosen merely as a refuge. Camps in these positions are never so imposing as those which crown hill-tops: the labour of excavating the ditches and heaping up the banks was not aided by the natural slope of a hill, and the earthworks, being slighter and nearer the more recent haunts of men, are more liable to destruction. But the defensive nature of such settlements is unmistakable.

The Roman invaders brought to England new methods of military construction and the tradition of an architecture of dressed and cemented stone. Their whole system of warfare was far in advance of that pursued by the British tribes. They had developed the art of siege to a high pitch. Their operations in open field were orderly and scientific. Their walled strongholds were constructed with a view which took into account, not only the mere strength of the ramparts, but also the capacity of the defenders to man them. Men, not fortresses, were the main asset of Roman warfare; and consequently their earthwork was far less imposing than that of the Britons of the prehistoric age. Their camps and permanent stations were usually surrounded by a single fosse of no great depth: the rare cases in which traces remain of more than a single fosse are camps upon the exposed northern frontier of Roman Britain, where the onrush of the barbarian enemy was stayed by a series of trenches, either covered with brushwood or filled with sharp stones or stakes. Camps were hastily constructed of earthwork; bank, ditch, and parapet playing their part. But where a camp became a permanent station a stone wall took the place of the earthen bank. The most important relic of the Roman occupation in Britain, the great frontier wall from the Tyne to the Solway, was preceded by a vallum of turf, a temporary defence which was superseded by permanent masonry.

No system of connected operations can be traced between prehistoric forts. Each of these was probably an isolated stronghold. Roman stations, on the other hand, were military posts manned by detachments of one army, and connected by strategic roads. This is seen very clearly in the case of the great wall already mentioned. The wall can be traced for about 73 miles, from Wallsend (Segedunum) on the Tyne to Bowness on the Solway. It is built in the usual Roman method, with a core of cemented rubble between ashlar facings. Its breadth varies between 7 and 9½ feet: the height appears to have been originally from 16 to 18 feet.6 Its northern face is defended by a ditch, marked a in the section below; but, as it follows the highest ground in its course, and runs for some distance along the edge of basaltic cliffs which dip northward, the ditch at these points becomes unnecessary and is dispensed with. There were twenty-three stations in its length, each garrisoned by a cohort of infantry or squadron of cavalry, chosen from the Roman auxiliary troops of Gauls, Spaniards, Moors, &c.7 These were connected by a paved military road (c) along the south side of the wall. At distances of a Roman mile from one another were placed rectangular forts, now known as mile-castles, built against the wall upon its south side; and the interval between each of these was strengthened further by turrets, apparently two in number, which also projected southward, but encroached slightly upon the thickness of the wall. The south side of the military road was defended by an earthen vallum, marked d,8 the course of which is not directly parallel to the wall, but is in places as much as half a mile distant, keeping to lower ground where the wall prefers the summit of the basalt ridge. This bank has a ditch (e) on its southern side, divided from it by a level space or berm: the ditch has a southern parapet (f), and another bank beyond (g). In certain places the ditch has also a northern parapet; but the general arrangement of the earthen ramparts is as described. Of the controversy as to the relative date of the wall and its flanking earthworks nothing need be said here. Its military purpose is abundantly clear. It provided not only a strong means of defence against the attacks of the northern tribes, but a base of operations for offensive warfare. Each of the stations and mile-castles has a northern gateway in addition to its other entrances; and two of the Roman roads which met the wall at intervals from the south passed through it on their way to the Scottish border.

Section of Roman Wall and Vallum.

The object of the great system of Roman roads was purely military.9 Along these broad paved “streets” the troops from the various stations could be mobilised with great quickness. They kept as a rule to high ground, choosing a convenient ridge, like that which runs from end to end of Lincolnshire, and preserving as straight a line as possible. The most important stations were placed at the crossing of rivers or at the junction of roads. In the early days of the Roman occupation, the operations of the army were directed entirely against the native tribes. No system of coast defence was adopted. The necessity for this came later, when Britain, under Roman dominion, was attacked by bodies of Saxon pirates. A chain of fortresses was then constructed along what was known as the Saxon shore, from Branodunum (Brancaster) in north Norfolk to Portus Adurni in Sussex or Hampshire. The remains of the walls of Gariannonum (Burgh Castle in Suffolk), Rutupiae (Richborough in Kent), Anderida (Pevensey in Sussex), and Portus Magnus (Porchester in Hampshire), are, next to the great wall, perhaps the most interesting relics of the Roman epoch which we possess. The forts of the Saxon shore were placed, for the most part, at the mouths of estuaries, for which the foreign pirates would naturally make.

Cilurnum

In several cases a Roman station was founded on the site of a British settlement. It was, however, more compact in plan, and occupied only a portion of the site. The earthworks defending the west side of the settlement which preceded Camulodunum (Colchester) are two to three miles beyond the Roman wall of the city, which occupied merely the north-east angle of a very large and straggling enclosure. The original Roman station at Lincoln may be taken as a typical example of a walled town of this epoch.10 It was a rectangular enclosure, with its longer axis from east to west, occupying the south-west angle of the high ridge above the valley of the Witham. In each of the four walls was a gateway. The inner arch and the postern, with part of the side walls, of the northern gateway still remain, and of the southern gateway there are still substantial fragments; the line of the street which led from one to the other is still fairly, though not accurately, preserved. The positions of the east and west gateways are known: the line of the street from the east gate to the centre of the city was deflected in the middle ages, but its continuation to the west gate is represented by the course of a street, much widened in modern times. Close to the meeting of the four streets was the market-place or forum. This, in the early days of Roman Lincoln, was the praetorium, or military headquarters of the camp. But the legion quartered at Lincoln was removed to York, as it seems, in the time of Vespasian, and the city settled down to a civil and commercial existence. Round the forum were clustered the chief public buildings of the city, and the foundations of a large colonnaded building are still to be seen below the present ground level. At Gloucester, Chichester, and Chester, the course of the four main streets has been little, if at all, disturbed, and their present meeting-place nearly represents the centre of the Roman city. The arrangements of the forum of a Romano-British town have been made out very clearly by the excavations at Calleva Atrebatum (Silchester) in Hampshire.11 It was a closed rectangle, entered by a gateway and surrounded by public buildings, in front of which were colonnades; one side at Silchester was occupied by a great basilica, which served the purposes of a hall of justice and mercantile exchange.

Borcovicus

The stations on the Roman wall were of a more purely military character than the towns which have been mentioned. They have the general characteristic of a rectangular plan, with the angles rounded off, and with a gateway, flanked by guard-houses, in each of the four sides. In the two largest stations, however, Amboglanna (Birdoswald) and Cilurnum (Chesters), there were, in addition to the main gateways, two smaller gateways in the east and west walls respectively.12 The walls of the stations are generally 5 feet thick, and are built, like the wall itself, of a core of cemented rubble, with facings of dressed stone. The main gateways have a double passage, divided by a longitudinal wall, which is pierced by a narrow passage in the centre. Their inner and outer openings were spanned by arches, and closed by gates which were hung on iron pivots fixed in the jamb of each opening next the wall. At Borcovicus (Housesteads) there was no dividing wall through the passage between the outer and inner openings of the gateway; but each of these openings is composed of two arches, divided by a square pier (15).13 Each gateway had a stone sill, raised above the level of the stone pavement. The interior passage was flanked by rectangular guard-houses. The gateways of Borcovicus show interesting signs of reconstruction, which point to the fact that, not long after its construction, the station was seized by an enemy. At a subsequent time, its Roman occupants reduced the width of the gateways by walling up one half of the double openings. This was done apparently at different times, the east gateway bearing signs of being treated in this way at an earlier period than the others. The west gateway was walled up with great ingenuity. Of its outer entrances, the northern, and of its inner entrances, the southern, were blocked; so that a foe, choosing this face of the station for attack, had to press his way through an elbow-shaped, instead of a straight passage.

Borcovicus; West Gateway

Pevensey

The wall of a Roman station, between the gateways, was often flanked by a series of towers, each projecting from the wall in the form of a semicircle or rather more than a semicircle. This was the case in some of the large Gallo-Roman cities, like Autun.14 While the rounded form of these towers made them difficult to undermine or batter down, their summits served as standing-ground for the large ballistae or catapults, from which javelins or stones could be hurled upon the attacking force. Their projection at regular intervals made it possible for the defenders to command the whole line of wall between each pair of towers; so that the besiegers’ attack would necessarily be concentrated upon the towers themselves. At Pevensey (16), where the enclosure of the station is almost oval, and not, as usual, rectangular, in shape, there are remains of twelve solid round towers, including those which flank the south-western gateway. At Burgh Castle there are four towers in the east wall, two of which are angle-towers.15 Owing to the scarcity of good building stone in the district, the walls at Burgh Castle are unfaced, and are built of flint with bonding courses of tiles; only the upper portions of the towers were bonded into the walls. A bed of concrete, with a platform of oak planks above, formed the foundation of the towers.16 The angles of the wall of Roman York were strengthened by large polygonal towers. A large portion of one of these, a magnificent example of Roman masonry, remains; it formed the north-western angle of the city, and was hollow, with an internal as well as an external projection (17). No outward projections appear to occur upon the Roman wall or in the walls of its stations. The “mile-castles,” as already noted, are built against the inner side of the wall. At Cilurnum (13) and Borcovicus there are foundations of square towers against and inside the containing walls, while the angles of the stations are simply rounded off. The western part of the north wall of Borcovicus has also been doubled in thickness, apparently to give a safe foundation for a large catapult planted on the top of the wall. The thickening was accomplished, at a date later than the original building, by constructing an inner wall, and filling up the space between this and the outer rampart with clay. At Cilurnum, which appears to have been in existence before the great frontier wall was made, the original east and west gateways were left on the north side of the wall, which intersects the station. As they were thus insufficiently protected, they were filled up solid with masses of rubble, and were probably used as platforms for catapults,17 smaller gateways being made on the south side of the wall.

York; Multangular Tower

Borcovicus; Praetorium

In the interior of the station, as at Lincoln, York, and Borcovicus, the main street, or via principalis, led directly from the north to the south gate.18 The centre of the station, west of the via principalis, was occupied by the praetorium, the headquarters of the commander of the legion, answering to the space where, in a temporary camp, the tents of the general and his staff were pitched. As we have seen, the place of the praetorium was taken in commercial towns by the forum. The praetorium at Borcovicus consisted of two rectangular courts, open to the sky in the centre. The outer court, with its main entrance facing the eastern street or via praetoria, was surrounded on three sides by a colonnade. A doorway, immediately opposite the main entrance, opened into the eastern colonnade of the inner court. This had no northern or southern colonnades, but had doorways to north and south: its western side was occupied by a line of five rectangular chambers, the central one of which was the chapel where the standards, with the other sacred treasures belonging to the cohort,19 were kept. The praetorium faced the eastern street of the station, which led to the east gate or porta praetoria. The gate at the end of the western street was called porta decumana.20 The remaining buildings of the station consisted of straight blocks, intersected by lanes: the majority of these buildings would be used as barracks. It should be noted that, in the planning of a Roman station or walled town, the praetorium or forum was taken as the central point: the via principalis, in order to run clear from gate to gate, was thus on one side of an axis of the rectangle, and the north and south gates21 were not in the centre of their respective walls.

It is clear that, as time went on and the power of Rome in Britain grew weaker, the defensive character of the great wall and that of the stations which it connected were emphasised at the expense of their character as bases of active warfare. But it must be repeated that Roman stations in Britain were not planned to form impregnable shelters for communities mainly pastoral. They were centres for bodies of fighting men, linked to each other by a splendid system of roads. The Roman station at Dorchester, the lines of which are so well preserved to-day, was founded, not within the ramparts of Maiden Castle or Poundbury, but on the lower slopes near the passage of the Frome. The single rampart and single ditch of a Roman town were almost invariable. Free egress as well as entrance, provisions for attack as well as defence, were necessary; and, with these objects in view, immense earthen defences, such as those of Maiden Castle, would be cumbersome. Bodies of Roman troops, as at Lincoln or Colchester, occasionally occupied part of the enceinte of a British settlement; but it is very rarely that, as in the case of Old Sarum, we find a British hill fort which also probably served as a Roman station. In this instance, the occupation of the fort was due, doubtless, to its neighbourhood to the military road: the road would not have been brought out of its way to include the fort in its course. Roman stations, although they differed in size, were small and compact, when contrasted with the large and straggling areas occupied by the British settlers. Suburbs naturally grew up outside their walls, and sometimes, although not very often, the walled enclosure was extended to include a growing outer district. This is supposed by many antiquaries to have happened at Lincoln, where the original Roman station occupied the summit of the hill north of the great bend of the Witham, which here turns from its northerly course due eastward. After the city of Lincoln had settled down to civil life, practically the whole slope of the hill south of the first enceinte was included within the city and encircled by a wall. Part of the east wall of this later enclosure is still visible: the Stonebow, the medieval south gate of the city, about a hundred yards from the river and the bridge, appears to be on the site of the later south gateway of Roman Lincoln.22