Military Architecture in England During the Middle Ages

by A. Hamilton Thompson

Many classical texts, from the time of Cæsar to the latest days of the western Empire, supply us with authority for Roman military methods. No passage throws fuller light on their siege practice than Cæsar’s description of his siege of Alesia in Burgundy, the hill fortress occupied by Vercingetorix.[65] The lines which were first drawn round the stronghold by Cæsar were eleven miles in circuit, and communicated with three camps, on hills of a height equal to that of the hill of Alesia. Along the lines there were twenty-three castella, small forts to hold pickets, and temporary examples of the type of which the “mile-castles” of the Roman wall were permanent instances. The stubborn resistance of Vercingetorix and the prospect of the arrival of a relieving army, however, gave Cæsar occasion to elaborate his lines, the character of which is very minutely described. They consisted of an earthen bank with a ditch 20 feet broad, 400 feet in front of it on the side towards the besieged stronghold. The ditch was dug with perpendicular sides: its distance from the bank was a precaution against sudden attacks of the enemy, and placed the bank out of the range of casual missiles. The space between the bank and ditch was not a level “berm,” but was furrowed by two ditches, 15 feet in breadth and depth, of which the inner was wet, the water of the neighbouring streams being diverted into it. Behind the inner ditch rose the earthen agger or bank, to the height of 12 feet. The vallum, the rampart on the top of the agger, was of a type common in early warfare and for many centuries later, consisting of a breastwork of interlaced twigs stiffened by a row of palisades. The hurdles of the breastwork were finished off with battlement-like projections: at intervals there were tall uprights with forked tops, which were called cervi or “stags,” and acted as chevaux-de-frise along the whole rampart. There were also towers, obviously temporary constructions of timber, at distances of 80 feet from one another. This, however, was not enough. Cæsar aimed at holding his lines with as few men as possible, so as to allow the rest to do the necessary foraging at a distance. He therefore proceeded to sow the approach to the lines with pitfalls. Five ditches, 5 feet deep, were dug out and filled with upright stakes sharpened to a point and fastened together at the bottom by continuous cross pieces. In front of these were three rows of pits, 3 feet deep, arranged in a series of quincunces or saltires: in these were placed smooth sharpened stakes, so that little more than their points stuck out of the ground, and the pits were then covered over with twigs and brushwood. The eight rows formed by these obstructions were each 3 feet apart. The whole arrangement, producing the effect of a row of fleurs-de-lys, was called lilium: to the stakes the soldiers gave the name of cippi or “grave-stones.” On the opposite side of the vallum, where an attack from a relieving army was expected, a similar arrangement was made. Also, in front of the lilium, wooden cubes with hooks fastened into them were hidden in the ground, bearing the appropriate name of stimuli.

Cæsar’s method of besieging Alesia was dictated by the probability that, with an enemy on both sides, he would have to stand a siege himself. After a doubtful battle, the Gallic army of relief made a night attack on the lines, in which they found to their cost the effectiveness of Cæsar’s death-traps. They brought with them hurdles, with which to help themselves across the ditches, and scaling ladders and grappling hooks, with the help of which they might climb or pull down the rampart. Their weapons were slings, arrows, and stones, to which the Romans replied with extemporised slings and spears. They suffered two repulses, and then turned their attention to the weakest of Cæsar’s camps, while Vercingetorix left Alesia to attack the rampart. His force brought hurdles with long balks of timber to form a footway across them, mantlets, or coverings under which an attacking party, sheltered from Roman missiles, could undermine or make a breach in Cæsar’s earthwork by the use of a bore, and hooks with which to cut down the rampart on the top of the earthen bank. The attack was long and determined. The Gallic pioneers filled up Cæsar’s fosses, so far as they could, with earth, and themselves raised a mound from which his devices of defence were easily seen. Where his lines were on level ground, they were too formidable to attack: on the steep slopes of the hills, on the tops of which his camps were pitched, there was more chance for an enemy. Here the fiercest fighting took place: the towers of the vallum were assailed with javelins, the ditch was filled, and an attempt was made to tear down the palisade and breastwork. Labienus, unable to hold the lines, sent a message to Cæsar, whose intervention with his cavalry turned the day and brought about the total defeat of the Gallic army and the surrender of Vercingetorix.

The account of the siege of Marseilles by Gaius Trebonius in B.C. 49 gives us many of the methods employed by the Romans, and by Byzantine and medieval engineers after them, in the siege of a walled town.[66] Marseilles was no mere hill stronghold like Alesia: it was a strongly fortified seaport town, well equipped for war with engines which hurled pointed stakes 12 feet long against the besiegers, as they threw up their earthen bank round the landward side of the city. Trebonius had to make the line of penthouses (vineæ), by which his pioneers were protected, of more than ordinary thickness to withstand these missiles. In advance of the bank, a body of men, sheltered by a large penthouse (testudo) levelled the soil. While this leaguer was established on the landward side, Brutus gained a naval victory over the Massiliotes, who nevertheless continued to hold out against the besiegers. The right wing of the Roman army was especially open to attack from the city; and on this side the besiegers built a tower of brick, to serve as a base of operations and a refuge from attack. This tower, which was raised to a height of six stories, was built by workmen who were sheltered by hanging mantlets of rope. A roof was made of timber, covered with a layer of bricks and puddled clay, to protect it against fire, and with raw hides, to make it proof against darts and stones. As the tower grew, this roof, from which the rope mantlets depended, was raised by levers and screwed down as a covering to each story in succession. When it was nearly completed, a wooden penthouse known as the mouse (musculus) was constructed, consisting of a gallery 60 feet long, with a gabled roof, which was covered, like that of the tower, with bricks, clay, and hide. This was moved forward on rollers to the nearest point in the city-wall. It withstood the huge stones which were cast upon it; lighted barrels of pitch and resin, hurled from the wall, rolled off its sloping roof and were pushed to a safe distance by the men inside, armed with poles and pitchforks. Covered by their friends’ fire from the brick tower, the soldiers in the mouse were able to sap with their levers and wedges the foundations of the tower on the wall, and managed to effect a breach. The defenders submitted, and asked for a truce until Cæsar arrived; but, taking advantage of the interval, they made a treacherous sally from the city, and, aided by a favourable wind, burned down the besiegers’ constructions, including the mouse and the brick tower, and destroyed their machines. Trebonius, however, lost no time in constructing, instead of his earthen bank, a strong wall of countervallation, composed of two parallel walls of brick, each 6 feet thick, with a timber floor above. This quickly brought the defenders to their senses, and they reverted to their old conditions of peace. In this account the devices which play the chief part are met again in numberless medieval sieges. The lines of countervallation, the successful sapping operation, appear, for example, in the tactics of Philip Augustus: the besiegers’ brick tower is met again in William Rufus’ timber castle at Bamburgh: the engines of war and the protected penthouses are commonplaces of medieval warfare.

The bare record of the Anglo-Saxon Chronicle throws little light to speak of upon the strategy or military skill of the Danes. Nor does the lyric form of the songs which celebrate the fight at Brunanburh and the battle of Maldon allow of that definiteness of detail which the student requires. More definite, although not unencumbered by rhetoric, is the account which Abbo, the monk of Saint-Germain-des-Prés, gives of the siege of Paris by the Northmen in 885-6.[67] The city of those days was confined to the isle still known as La Cité, and was united to its suburbs on the mainland by two bridges, where now are the Pont-au-Change and the Petit-Pont. The approach to each bridge was guarded, on the mainland, by a tower or tête-du-pont. The attack of the Normans was directed against the northern tower, the construction of which had not been finished. It is curious to notice how they concentrated themselves on single points in the defence, neglecting the prime necessity of closing all lines of communication to the defenders. They came up to the tower with their ships, which were seven hundred in number, not counting sailless boats, battered it with their engines, and hurled darts at its defenders. The tower was shaken, but its foundations stood firm: where the walls threatened to give, they were repaired with planks of timber, and the tower was raised by these wooden additions during a night to one and a half times its former height. At daybreak the Northmen again began the attack. The air, says Abbo, was full of arrows and stones flung from slings and from the ballistae or hurling machines. During the day the heightened tower showed signs of succumbing to the enemy’s fire and their mining efforts. Eudes, the brave defender of the town, poured down a mixture of burning oil, wax, and pitch, which quenched the enthusiasm of the besiegers, and cost them three hundred men. On the third day, the Northmen established their land camp on the northern bank of the river, near the church of Saint-Germain-l’Auxerrois. The camp was probably a geweorc such as they wrought by the Thames or the Ouse, but it was girt, not with an earthen rampart, but with walls of clay mingled with stone. From this centre they cruelly ravaged the surrounding country during the remainder of the siege. Having thus established their base of operations, they returned to the attack of the tower. Their devices were the common devices of Roman warfare, which naturally would recommend themselves to the assailants of the dying Roman civilisation. We hear of the three great battering rams which they prepared, and moved up against the walls under the shelter of wooden penthouses on wheels, of the bores brought up to undermine the tower by men moving under wicker mantlets covered with raw hides, of the mangana or stone-throwing machines used by the defenders, and of the forked beams let down from the tower to catch the heads of the battering-rams and render them powerless. Some of the Northmen worked at filling up the ditches with whatever came to hand, earth, leaves, straw, meadow grass, cattle, even the bodies of captives. Still the city held out, and Eudes managed to slip through the enemy’s lines and reach Charles the Fat with a request for relief. On his return the Northmen tried to intercept him: he got back safely into Paris, while a relieving force attacked the enemy and drove them back on their ships. When Charles the Fat arrived he established his camp on the southern slopes of Montmartre; but he was content, after a general attack upon the city had failed, to let the Northmen go, taking with them an indemnity of seven hundred pounds, and promising to leave the kingdom in March. They, however, made an attempt to reach the upper Seine in boats, as the larger vessels could not clear the bridges, and so proceed to pillage Burgundy. Their purpose was discovered: the defenders of Paris launched arrows at them from the walls, and a chance dart killed their pilot. For a time their onward course was checked, but a series of such assaults could not be sustained by the French. Eudes, elected king, neglected the conflict, and gave words for deeds. “Their barks,” says Abbo, “were in crowds on all the rivers of Gaul.” He ends his poem with a call to France to give proof once more of those forces which she had used in the past to conquer kingdoms more powerful than herself. “Three vices,” he cries, “are causes of thy ruin: pride, the shameful love of pleasures, the vain lust of gorgeous apparel.” The same words might have been said to the English a hundred and twenty-five years later, when Swegen and Thurkill were gripping London between their two armies.

A short passage in the Anglo-Saxon Chronicle affords some help to the question of Danish strategy. London bridge, like the two bridges of Paris, was an obstacle to the long Danish ships with their sails. In 1016, however, the Danes managed to drag their ships round the south side of the bridge, apparently by making a ditch on that side of the river. They then proceeded to make entrenchments about the city, their headquarters being thus removed above bridge. There is no reason to doubt that the London which they thus beset was a stone-walled city, the Roman Londinium which Alfred had repaired. So was Paris, and so were a large number of the towns of France, whose walls had been set in repair by their bishops or lay lords. We read of Saint Didier, bishop of Cahors 630-55, that he “enlarged, built, and made strong Cahors with abundant labour, and a notable work of defence, fortifying gates and towers with a girdle of walls compacted of squared stones.” In the next century the Saracen invaders of southern France restored the Roman walls of Narbonne, and checked the advance of Charles Martel into Spain.[68] But for the many instances in which the fortifications of Roman cities in France played a part in the warfare of this troubled epoch, there are few in England. The burhs of the Danish wars were, with the exception of London, Towcester, Colchester, and a few more, not stone-walled cities of Roman foundation, such as those which in France were the natural prey of the Norman marauders, but villages or small towns which had grown into existence for the most part since the Saxon conquest, and owed their strength to walls of timber. In France military art, as regards both fortification and siege-craft, was altogether on a higher plane. The break of continuity caused by the extinction of Roman civilisation in England produced a stage in the development of attack and defence to which contemporary French history affords no parallel. It is not till a later period that the finished methods employed by both sides in the siege of Paris were used in English warfare.

The cases hitherto quoted refer to sieges of towns; and, as we have seen, the castle or private fortress which plays so prominent a part in medieval strategy was the result of the growth of the feudal system, and takes its place in history at a comparatively late period. A fortified town of Roman origin possessed its arx or citadel: this was, as it were, the keep of the walled enclosure, to which the defenders could retire if the outer defences of the town were taken. A castle, however, was a distinct enclosure, which frequently occupied a portion of the area of a walled town, but had its own outer lines of defence before the keep could be reached. The Norman conquerors of England, regarding the castle as the main seat of defence and object of attack, directed their attention to its fortification; and thus the defence of the town or village in or near which the castle stood became of secondary interest. We usually find that, where a castle forms part of the defences of an English walled town, the castle has been surrounded with a wall and provided with its necessary defences before a wall has been built round the town in place of the earlier palisade. In spite, however, of this change in the nature of the besieged stronghold, the object of attack was still a fortified enclosure. The methods of siege developed along the old lines; and the defences applied to the castle were those which, on a more extended scale, were applicable to the town.

The warfare of the eleventh and twelfth centuries was to a great extent a succession of sieges of castles, by direct attack or by blockade. In 1083 William the Conqueror, besieging Hubert of Maine in the castle of Ste-Suzanne, did not venture to attack the wooded precipice on which the castle stood, but entrenched his army within earthworks in a neighbouring valley. The blockade lasted three years, and the advantage lay much on the side of Hubert, so that eventually the Norman army, after a desperate attack had failed, withdrew.[69] The chief feature of the blockade was the construction of an opposition castle,[70] a method employed upon more than one occasion by William II., who, in 1088, compelled Odo to surrender Rochester castle by making two castella upon his lines of communication.[71] In 1095 William II. besieged Robert Mowbray in Bamburgh castle. The great rock, with its girdle of sea and marsh, did not lend itself to direct attack, and William compelled its surrender by building a “new fortress,” which took the form of a timber castle, probably of the ordinary mount-and-bailey type, and was nicknamed Malvoisin, the “ill neighbour.”[72] From this particular instance, the name of malvoisin has been applied generally, without sufficient reason, to the wooden towers which were sometimes constructed to shelter a besieging force. As a matter of fact, Malvoisin was merely one of many nicknames which were given, in individual cases, to such besiegers’ castles,[73] and was no more a generic term than is Château-Gaillard.

Until the end of the eleventh century, when the first Crusade taught western warriors the use of more advanced siege-engines, the methods of attack upon a castle seem to have been of a very simple description. Earthworks defended by timber could be gained by a rush and hand-to-hand fighting; while fire would always be fatal to a wooden stronghold ill provided against it. The Bayeux tapestry shows us none of those siege-machines which were employed more and more frequently against stone castles during the next century; and, although the Conqueror’s army seem to have employed an elementary form of stone-throwing machine, handled, like the later cross-bow, by individual soldiers, and other devices more familiar in later times,[74] such machines can hardly have been common. It was, no doubt, their growing frequency at the beginning of the twelfth century which made stone walls imperative for the protection of a castle. We have seen ballistae and other siege-engines of Roman origin used by the Northmen at the great siege of Paris in 885; but such engines were certainly not in common use in western Europe before the period of direct contact with Byzantine civilisation. Ordericus Vitalis mentions the construction of such machines, a “belfry” on wheels and devices for hurling large stones, by Robert of Bellême’s engineer at Bréval in 1093, as though they were a novelty, and says of the engineer himself that his sagacious ingenuity had been of profit to the Christians at the siege of Jerusalem.[75]

Suger’s detailed account of the attack made by Louis VI. upon the castle of Le Puiset in 1111 may be taken as a fair description of the methods employed by the besiegers and defenders of an ordinary castle of earthwork and timber. The king brought numerous ballistae to the attack, but we have no indication as to their precise nature: the main weapons employed were the bow, sword, and shield. The besieged came out of the castle to meet the king; but, amid a hail of arrows from both sides, were driven back through the main gateway, which was possibly, as at Tickhill,[76] the only stone defence of the enclosure. From the rampart of their stronghold, they hurled down wooden planks and stakes upon the king’s knights. The besiegers, throwing away their broken shields, made use of the missiles to protect themselves and force the gateway. Carts laden with dry wood smeared with fat were brought up to the doors, and a struggle took place, the royalists trying to set the wood on fire, the defenders trying to put the fire out. Meanwhile Theobald of Chartres made an attack on the castle from another quarter, attempting to climb the steep scarp of the bailey. His followers, however, were too hasty: many fell back into the ditch, while others were surprised and killed by horsemen of the enemy, who galloped round the defences of the castle to keep out intruders. The royalists had almost given up hope, when a priest, bare-headed and holding before him a piece of wood as an extemporised mantlet, reached the palisade, and began to tear away the planks which covered the spaces between the uprights. He was soon joined by others, who cut away the palisade with axes and iron tools. The royal army poured into the castle, and the defenders, taken between the entering force and Theobald’s men, retired into the timber tower on the mount, but surrendered in fear. The king burned the castle, but spared the donjon.[77]