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FORTIFICATION AND SIEGECRAFT
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FORTIFICATION AND SIEGECRAFT . " Fortification " is the military See also:art of strengthening positions against attack . The word (See also:Lat. fortis, strong, and facere, to make) implies the creation of defences . Thus the boy who from the See also:top of a See also:mound defies his comrades, or shelters from their snowballs behind a fence, is merely taking See also:advantage of ground; but if he puts up a See also:hurdle on his mound and stands behind that he has fortified his position . Fortification consists of two elements, viz. See also:protection and obstacle . The protection See also:shields the defender from the enemy's missiles; the obstacle prevents the enemy from coming to See also:close quarters, and delays him under See also:fire . Protection may be of several kinds, See also:direct or indirect . Direct protection is given by a See also:wall or rampart of See also:earth, strong enough to stop the enemy's missiles . The value of this is reduced in proportion as the defender has to expose himself to return the enemy's fire, or to resist his attempts to destroy the defences . Indirect protection is given by distance, as for instance by a high wall placed on a cliff so that the defender on the top of the wall is out of reach of the enemy's missiles if these are of See also:short range, such as arrows . This See also:kind of See also:defence was very popular in the See also:middle ages . In the See also:present See also:day the same See also:object is attained by pushing out detached forts to such a distance from the See also:town they are protecting that the besieger cannot See also:bombard the town as See also:long as he is outside the forts . Another See also:form of indirect protection of See also:great importance is concealment . The obstacle may consist of anything which will impede the enemy's advance and prevent him from coming to close quarters . In the earliest forms of fortification the protecting wall was also the obstacle, or it may be a wet or dry ditch, an entanglement, a swamp, a See also:thorn hedge, a spiked palisade, or some temporary expedient, such as crows' feet or chevaux de frise . The two elements must of course be arranged in See also:combination . The besieged must be able to defend the obstacle from their protected position, otherwise it can be surmounted or destroyed at leisure . But a close connexion is no longer essential . The effect of See also:modern firearms permits of great See also:elasticity in the disposition of the obstacle; and this simplifies some of the problems of defence . Protection must be arranged mainly with reference to the enemy's methods of attack and the weapons he uses . The obstacle, on the other See also:hand, should be of such a nature as to bring out the best effects of the defender's weapons . It follows from this that a well-armed force operating against a badly-armed uncivilized enemy may use with advantage very See also:simple old-fashioned methods of protection; or even dispense with it altogether if the obstacle is a See also:good one . When the assailant has modern weapons the importance of protection is very great . In fact, it may be said that in proportion as missile weapons have grown more effective, the importance of protection and the difficulty of providing it have increased, while the See also:necessity for a monumental See also:physical obstacle has decreased .
The art of the engineer who is about to fortify consists in appreciating and harmonizing all the conditions of the problem, such as the weapons in use, nature of the ground, materials available, See also:temper of assailants and defenders, strategical possibilities, See also:expenditure to be incurred, and so forth
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Few of these conditions are in themselves difficult to understand, but they are so many and their reactions are so complex that a real familiarity with all of them is essential to successful See also:work
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The keynote of the See also:solution should be simplicity; but this is the first point usually lost sight of by the makers of " systems," especially by those who during a long See also:period of See also:peace have. See also:time to give See also:play to their imaginations
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Fortification is usually divided into two branches, namely permanent fortification and See also:
The feudal castles lost their importance when the art of See also:cannon-See also:founding was fairly See also:developed; and in the leisurely See also:wars of the 17th and 18th centuries, when roads were few and See also:bad, a swarm of fortified towns, large and small, played a great See also:part in delaying the See also: The latter were built in at right angles to the length of the See also:parapet, and were thus very difficult to displace, while the earth prevented their being set on fire . The bank was often strengthened by a palisade of tree trunks or hurdle-work . After the bank the most important step in advance for a nation progressing in the arts was the wall, of See also:masonry, See also:sun-dried See also:brick or niud . The history of the development of the wall and of the methods of attacking it is the history of fortification for several thousand years . The first necessity for the wall was height, to give security against escalade . The second was thickness, so that the defenders might Irave a See also:platform on the top which would give them space to circulate freely and to use their weapons . A lofty wall, thick enough at the top for purposes of defence, would be very ex-pensive if built of solid masonry; therefore the See also:plan was See also:early introduced of See also:building two walls with a filling of earth or See also:rubble between them . The See also:face of the See also:outer wall would be carried up a few feet above the platform, and crenellated to give protection against arrows and other projectiles . The next forward step for the defence was the construction of towers at intervals along the wall . These provided flanking fire along the front; they also afforded refuges for the See also:garrison in See also:case of a successful escalade, and from them the platform could be enfiladed . The See also:evolution of the wall with towers was simple . The See also:main requirements were despotic See also:power and unlimited labour . Thus the finest examples of the See also:system known to history are also amongst the earliest . One of these was Nineveh, built more than z000 years B.C . The object of its huge perimeter, more than 5o m., has been mentioned . The wall was 120 ft. high and 30 ft. thick; and there were 15oo towers . After this no See also:practical advance in the art of fortification was made for a very long time, from a constructional point of view . Many centuries indeed elapsed before the inventive See also:genius of See also:man evolved engines and methods of attack See also:fit to See also:cope with such See also:colossal obstacles . The earliest form of attack was of course escalade, either by ladders or by heaping up a ramp of faggots or other portable materials . When the increasing height of walls made escalade too difficult, other means of attack had to be invented . Probably the first of these were the See also:ram, for battering down the walls, and See also:mining . The latter might have two objects: (a) to drive an underground See also:gallery below the wall from the besiegers' position into the fortress, or (b) to destroy the wall itself by undermining . The use of missile engines for throwing heavy projectiles probably came later . They are mentioned in the preparations made for the defence of See also:Jerusalem against, the See also:Philistines in the 8th See also:century B.C .
They are not mentioned in connexion with the See also:siege of See also:Troy
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At the sieges of See also:Tyre and Jerusalem by Nebuchadnezzar in 587 B.C. we first find mention of the ram and of movable towers placed on mounds to overlook the walls
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The Asiatics, however, had not the qualities of mind necessary for a systematic development of siegecraft, and it was See also:left for the Greeks practically to create this See also:science
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Taking it up in the 5th century B.C. they soon, under See also:
The towers were preferred circular in plan, as this form offered the
re-Conditions best resistance to the See also:rain
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The wall was usually re-
n in enforced by a ditch, which had three advantages: it of op ng increased the height of the obstacle, made the bringing Chrithe stian up of the engines of attack more difficult, and supplied era. material for the filling of the wall
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In See also:special cases, as at
]erusalem and See also:Rhodes, the enclosure walls were doubled and trebled
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Citadels were also built on a large See also:scale
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The typical site preferred by the Romans for a fortified town was on high ground sloping to a See also:river on one See also:side and with steep slopes falling away on the other three sides
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At the highest point was a See also:castle serving as citadel
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The town enclosure was designed in accordance with the See also:character of the surrounding country
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Where the enemy's approach was easiest, the walls were higher, flanking towers stronger and ditches wider and deeper
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Some of the towers were made high for look-out posts
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If there was a See also:bridge over the river, it was defended by abridge-See also:head on the far side; and stockades defended by towers were built out from either bank above and below the bridge, between which chains or booms could be stretched to See also:bar the passage
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The natural features of the ground were skilfully utilized
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Thus when a large town was spread over an irregular site broken by hills, the See also:enceinte wall would be carried over the top of the hills; and in the intervening valleys the wall would not only be made stronger, but would be somewhat See also:drawn back to allow of a flanking defence from the See also: The walls would consist of two strong masonry faces, 20 ft. apart, the space between filled with earth and stones . Usually when the See also:lie of the ground was favourable, the outside of the wall would be much higher than the inside, the parapet walk perhaps being but a little above the level of the town . Palisades were used to strengthen the ditches, especially before the See also:gates . There was little See also:scope, however, in masonry for the genius of Roman warfare, which had a better opportunity in the active work of attack and defence . For siegecraft the Roman legions were specially See also:apt . No modern engineer, See also:civil or military, accustomed to rely on machinery, See also:steam and See also:hydraulic apparatus, could See also:hope to emulate the feats of the legionaries . In earthworks they ex-celled; and in such work as building and moving about colossal wooden towers under war conditions, they accomplished things at which nowadays we can only wonder . The attack was carried on mainly by the use of+" engines," under which head were included all mechanical means of attack—towers, missile engines such as catapults and balistae, rams of different kinds, " tortoises " (see below), &c . Mining, too, was freely resorted to, also approach trenches, the use of which had been introduced by the Greeks . The object of mining, as has been said, might be the See also:driving of a gallery under the wall into the interior of the See also:place, or the destruction of the wall . The latter was effected by excavating large See also:chambers under the See also:foundations . These were supported while the excavation was proceeding by timber struts and planking . When the chambers were large enough the timber supports were burnt and the wall collapsed . The besieged replied to the mining attack by See also:counter-mines . With these they would undermine and destroy the besiegers' galleries, or would break into them and drive out the workers, either by force of arms or by filling the galleries with See also:smoke . Breaches in the wall were made by rams . These were of two kinds . For dislodging the cemented masonry of the face of the wall, See also:steel-pointed heads were used; when this was done, another head, shaped like a ram's head, was substituted for battering down the filling of the wall . For escalade they used ladders fixed on wheeled platforms; but the most important means of attack against a high wall were the movable towers of See also:wood . These were built so high that from their tops the parapet walk of the wall could be swept with arrows and stones; and drawbridges were let down from them, by which a storming party could reach the top of the wall . The height of the towers was from 70 to 150 ft . They were moved on wheels of solid See also:oak or See also:elm, 6 to 12 ft. in See also:diameter and 3 to 4 ft. thick . The ground See also:floor contained one or two rams .. The upper floors, of which there might be as many as fifteen, were furnished with missile engines of a smaller kind . The archers occupied the top floor . There also were placed reservoirs of See also:water to extinguish fire . These were filled by force pumps and fitted with See also:hose made of the intestines of See also:cattle . Drawbridges, either See also:hanging or worked on rollers,, were placed at the proper height to give See also:access to the top of the wall, or to a See also:breach, as might be required . See also:Apollodorus proposed to place a couple of rams in the upper part of the See also:tower to destroy the crenellations of the wall . The siege towers had of course to be very solidly built of strong timbers to resist the heavy stones thrown by the engines of thedefence . They were protected against fire by screens of osiers, plaited rope or raw hides . Sometimes it was necessary, in See also:order to gain greater height, to place them on high terraces of earth . In that case they would be built on the site . At the siege of See also:Marseilles, described by Caesar, special methods of attack had to be employed on See also:account of the strength of the engines used by the besieged and their, frequent sallies to destroy the siege See also:works . A square fort, with brick walls 30 ft. long and 5 ft. thick, was built in front of one of the towers of the town to resist sorties . This fort was subsequently raised to a height of six storeys, under shelter of a roof which projected beyond the walls, and from the See also:eaves of which hung heavy mats made of See also:ships' cables . The mats protected the men working at the walls, and as these were built up the roof was gradually raised by the use of endless screws . The roof was made of heavy beams and planks, over which were laid bricks and See also:clay, and the whole was covered with mats and hides to prevent the bricks from being dislodged . This structure was completed without the loss of a man, and could only have been built by the Romans, whose soldiers were all skilled workmen . Although these towers were provided with bridges by which storming parties could reach the top of the wall, their main object was usually to dominate the defence and keep down the fire from the walls and towers . Under this protection breaching operations could be carried on . The approaches to the wall were usually made under shelter of galleries of timber or hurdle-work, which were placed on wheels and moved into position as required . When the wall was reached, a shelter of stronger construction, known as a " See also:rat," was placed in position against it . Under this a ram was swung or worked on rollers; or the rat might,be used as a shelter for miners or for workmen cutting away the face of the wall . The great rat at Marseilles, which extended from the tower already described to the See also:base of the tower of the See also:city, was 6o ft. long, and built largely of great beams 2 ft. square, connected by See also:iron pins and bands . It was unusually narrow, the ground sills of the side walls being only 4 ft. apart . This was no doubt in order to keep down the See also:weight of the structure, which, massive as it was, had to be movable . The sloping roof and sides of timber were protected, like those of the tower, with bricks and moist clay, hides and See also:wool mattresses . Huge stones and barrels of blazing See also:pitch were thrown from the wall upon this rat without effect, and under its See also:cover the soldiers loosened and removed the foundations of the tower until it See also:fell down . In order that it might be possible to move these heavy structures, it was usually necessary to fill up the ditch or to level the See also:surface of the ground . For this purpose an " approach See also:tortoise " was often used . This was a shelter, something between the See also:ordinary gallery and the rat, which was moved end on towards the wall, and had an open front with a See also:hood, under cover of which the earth brought up for filling the ditch was distributed . The missile engines threw stones up to 600 lb weight, heavy darts from 6 to 12 ft. long, and See also:Greek fire . See also:Archimedes at the siege of See also:Syracuse even made some throwing "Soo lb . The ranges varied, according to the See also:machine and the weight thrown, up to 60o yds. for direct fire and 1000 yds. for curved fire . At the siege of Jerusalem See also:Titus employed three See also:hundred catapults of different sizes and See also:forty balistae, of which the smallest threw missiles of 75 lb weight . At See also:Carthage Scipio found 120 large and 281 See also:medium catapults, 23 large and 52 small balistae, and a great number of scorpions and other small missile engines . Screens and mantlets for the protection of the See also:engine-workers were used in great variety . In addition to the above, great mechanical skill was shown in the construction of many kinds of See also:machines for occasional purposes . A kind of jib See also:crane of great height on a movable platform was used to hoist a cage containing fifteen or twenty men on to the wall . A long spar with a steel claw at the end, swung in the middle from a lofty See also:frame, served to pull down the upper parts of parapets and overhanging galleries . The defenders on their side were not slow in replying with similar devices . Fenders were let down from the wall to soften the See also:blow of the ram, or the ram heads were caught and held by See also:cranes . Grapnels were lowered from cranes to seize the rats and overturn them . Archimedes used the same idea in the defence of Syracuse for lifting and sinking the Roman galleys . Wooden towers were built on the walls to overtop the towers of the besiegers . Many devices for throwing fire were employed . The tradition that Archimedes burnt the Roman See also:fleet, or a portion of it, at Syracuse, by focusing the rays of the sun with reflectors, is supported by an experiment made by See also:Buffon in 1747 . With a reflector having a surface of 50 sq. ft., made up of 168 small mirrors each 6 by 8 in., See also:lead was melted at a distance of 140 ft. and wood was set on fire at 16o ft . The development of masonry in permanent fortification had long since reached its practical limit, and was no longer See also:proof against the destructive methods that had been evolved . The extemporized defences were, as is always the case, worn down by a resolute besieger, and the attack was stronger than the defence . Through the dark ages the Eastern Empire kept alive the twin sciences of fortification and siegecraft long enough for the Crusaders to learn from them what had been lost in the See also:West, See also:Byzantium, however, always a storehouse of military science, while conserving a knowledge of the ancient methods and middle to fortification, so far as we know . In practice the ages . the great missile engines, contributed no new ideas nothing of it, and the efforts of See also:Charlemagne and others of the Frankish See also:kings to restore the art were hampered by the fact that their warriors despised handicrafts and understood nothing but the use of their weapons . During the dark ages the towns of the Gauls retained their old Roman and Visigoth defences, which no one knew properly how to attack, and accordingly the sieges of that period dragged themselves out through long years, and if ultimately successful were so as a See also:rule only through See also:blockade and See also:famine . It was not until the Ilth century that siegecraft was revived in the West on the ancient lines . By this time a new departure of great importance Byzantines favoured multiplied enceintes or several concentric lines of defence . This of course is always a tendency of decadent nations . In the West the Roman fortifications remained See also:standing, and the Visigoths, See also:allies of See also:Rome, utilized their principles in the defences of See also:Carcassonne, See also:Toulouse, &c. in the 5th century . See also:Viollet-le-Duc's description and illustrations of the defences of Carcassonne will give a very good idea of the methods then in use: " The Visigoth fortification of the city of Carcassonne, which is still preserved, offers an analogous arrangement recalling those described by See also:Vegetius . The level of the town is much more elevated than the ground outside, and almost as high as the parapet walks . The See also:curtain walls, of great thickness, are composed of two faces of small cubical masonry alternating with courses of brick; the middle portion being filled, not with earth but with rubble run with See also:lime . The towers were raised above these curtains, and their com- munication with the latter might be cut off, so as to make of each tower a small inde- pendent fort; ex- ternally these towers are cylindrical, and on the side of the town square; they See also:rest, also towards the country, upon a cubical base or See also:foundation . We subjoin (fig . I) the plan of one of these towers with the cur- tains adjoining . A is the plan of the ground-level ; B the plan of the first See also:storey at the level of the parapet . We see, at C and D, the two excavations formed in front of the gates of the tower to intercept, when the drawbridges were raised, all communication between the town or the parapet walk and the several storeys of the tower . From the first storey access was had to the upper crenellated or battlemented portion of the tower by a See also:ladder of wood placed interiorly against the side of the See also:flat wall . The See also:external ground-level was much See also:lower than that of the tower, and also beneath the ground-level of the town, from which it was reached by a descending See also:flight of from ten to fifteen steps . Fig . 2 shows the tower and its two curtains on the side of the town; the bridges of communication are supposed to have been removed . The battlemented portion at the top is covered with a roof, and open on the side of the town in order to permit the defenders of the tower to see what was going on therein, and also to allow of their hoisting up stones and other projectiles by means of a rope and See also:pulley . Fig . 3 shows the same tower on the side towards the country; we have added a See also:postern, the See also:sill of which is sufficiently raised above the ground to necessitate the use of a scaling or step ladder, to obtain See also:ingress . The postern is defended, as was customary, by a palisade or barrier, each See also:gate or postern being provided with a work of this kind." Meanwhile, in western See also:Europe, siegecraft had almost disappeared . Its perfect development was only possible for an army like that of the Romans . The See also:Huns and Goths knewhad been castles . made in the seigneurial castle (q.v.), which restored for some centuries a definite superiority to the defence . Built primarily as strong-holds for local magnates or for small bodies of warriors dominating a conquered country, the conditions which called them into existence offered several marked advantages . The defences of a town had to follow the growth of the town, and would naturally have weak points . It was not to be expected that a town would develop itself in the manner most suitable for defence; nor indeed that any position large enough for a town could be found that would be naturally strong all See also:round . But the site of a castle could be chosen purely for its natural strength, without regard, except as a secondary See also:consideration, to'the protection of anything outside it; and as its See also:area was small it was often easy to find a natural position entirely suited for the purpose . In fact it frequently happened that the existence of such a position was the raison d'etre of the castle . A small hill with steep sides might well be unapproachable in every direction by such cumbrous structures as towers and rats, while the height of the hill, added to the height of the walls, would be too much for the besiegers' missiles . If the sides of the hill were precipitous and rocky, mining became impossible, and the site was perfect for defence . A castle built under such conditions was practically impregnable; and this was the cause of the See also:independence of the barons in the 11th and See also:Lath centuries . They could only be reduced by blockade, and a blockade of long duration was very difficult in the feudal age . A very instructive example of 12th-century work is the See also:Chateau See also:Gaillard, built by See also:Richard Cceur-de-See also:Lion in 1196 . This great castle, with ditches and escarpments cut out of the solid See also:rock, and extensive outworks, was completed in one See also:year . In the See also:article CASTLE will be found the plan of the main work, which is here supplemented by an See also:elevation of the See also:donjon (or keep) . The waved face of the inner or main wall of the castle, giving a divergent fire over the front, is an interesting feature in advance of the time . So also is the masonry protection of the See also:machicolation at the top of the donjon, a protection which at that time was usually given by wooden hoardings . After the See also:death of Richard, Philip See also:Augustus besieged the chateau, and carried it after a blockade of seven months and a See also:regular attack of one See also:month . In this attack the tower at A was first See also:mined, after which the whole of that outwork was abandoned by the defenders . The outer enceinte was next captured by surprise; and finally the gate of the main wall was breached by the pioneers . When this happened a sudden See also:rush of the besiegers A outside view . prevented the remains of the garrison from gaining the shelter of the donjon, and they had to See also:lay down their arms . Chateau Gaillard, designed by perhaps the greatest general of his time, exemplifies in its brief resistance the weak points of the designs of the 12th century . It is easy to understand how at each step gained by the besiegers the very difficulties which had been placed in the way of their further advance prevented the garrison from reinforcing strongly the points attacked . In the 13th century many influences were at work in the development of castellar fortification . The experience of such sieges as that of Chateau Gaillard, and still more that gained in the See also:Crusades, the larger garrisons at the disposal of the great feudal lords, and the importance of the interests which they had to protect in their towns, led to a freer See also:style of See also:design . We must also take See also:note of an essential difference between the forms of attack preferred by the Roman soldiery and by the See also:medieval See also:chivalry . The former, who were artisans as well as soldiers, preferred in siege works the certain if laborious methods of breaching and mining . The latter, who considered all See also:manual labour beneath them and whose only ideal of warfare was See also:personal combat, affected the tower and its bridge, giving access to the top of the wall rather than the rat and battering-ram . They were also fond of surprises, which the bad discipline of the time favoured . We find, therefore, important progress in enlarging the area of defence and in improving arrangements for flanking . The size and height of all works were increased . The keep of See also:Coucy Castle, built in 1220, was 200 ft. high . See also:Montargis Castle, also built about this time, had a central donjon and a large open enclosure, within which the whole garrison could move freely, to reinforce quickly any threatened point . The effect of flanking fire was increased by giving more See also:projection to the towers, whose sides were in some cases made at right angles to the curtain walls . We find also a tendency, the See also:influence of which lasted long after medieval times, towards complexity and multiplication of defences, to guard against surprise and localize successful assaults . Great See also:attention was paid to the " step by step " defence .
Flanking towers were cut off from their walls and arranged for See also:separate resistance
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Complicated entrances with traps and many doors were arranged
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Almost all defence was from the tops of the walls and towers, the loopholes on the lower storeys being mainly for light and See also:air and reconnoitring
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Machicouli galleries (for See also:vertical defence) were protected either by See also: |