How Did Medieval Castles Work? Walls, Sieges and the End of the Fortress
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A castle was not a fort. Forts are for soldiers; a castle was the fortified house of a lord, his family, his household and his garrison, and its purpose was as much to hold the land around it as to keep enemies out. From the Norman conquest of 1066 the English countryside sprouted hundreds of them within a generation, and for four centuries their walls dictated how wars were fought, until a new kind of weapon made walls a liability and the lords moved into houses with windows.
From earth to stone
The first castles were quick. A motte-and-bailey was a mound of earth, the motte, thrown up in weeks by forced labour, with a wooden tower on top and a fenced yard, the bailey, at its foot; William the Conqueror's men built dozens across England to hold a hostile country, and the Bayeux Tapestry shows one going up. Wood rots and burns, and from the late eleventh century the towers were rebuilt in stone as keeps, square blocks with walls three or four metres thick and the entrance on the first floor, as at the Tower of London and Rochester. A keep was a last refuge more than a fighting platform, and its corners were its weakness: at Rochester in 1215 King John's miners brought down one of them by burning forty pigs' worth of fat under the foundations, and the corner was rebuilt round.
The concentric castle
The crusaders came home from the east with new ideas, and the castles of the thirteenth century put the strength in the walls rather than the keep. Edward I's castles in Wales, built in the 1280s by a Savoyard master mason, are the type: a ring of high curtain wall studded with round towers that let archers shoot along the wall's face, inside a lower outer ring, so that attackers who took the outer wall stood in a killing ground below the inner one. The gate, the weakest point, became the strongest, a gatehouse with several sets of doors and portcullises, murder holes in the ceiling and a drawbridge in front. The features and what they were for:
- •Round towers: no corners to mine, and no blind spots for defenders
- •Arrow slits: narrow on the outside, splayed on the inside, so an archer could aim widely while presenting a target a few centimetres across
- •Machicolations: overhanging galleries at the top of the wall with holes in the floor, for dropping stones on anyone at its base
- •The moat: water or a dry ditch, which stopped siege towers and rams reaching the wall and made mining under it impossible
- •The barbican: an outwork in front of the gate that forced attackers to approach along a channel under fire
Sieges
A castle was rarely stormed. The usual siege was a blockade, in which the attacker surrounded the place and waited for the food, water or will to run out, while trying to shorten the wait. Trebuchets, counterweight catapults that could throw a hundred-kilogram stone a couple of hundred metres, battered the walls and lobbed dead animals over them to spread disease; siege towers rolled up to the wall on wheels so that troops could cross at the top; battering rams under roofs of wet hides attacked gates; and miners dug tunnels under a tower, propped them with timber, and burned the props so that the wall above collapsed, which the defenders answered by counter-mining and fighting underground by candlelight. A well-supplied castle could hold for months, and a besieging army, sitting in its own filth, often died faster than the garrison; many sieges ended by negotiation, with the garrison marching out under terms if no relief had come by an agreed date.
Life inside
In peacetime, which was most of the time, a castle was a manor house with thick walls. The great hall was the centre, where the household ate, the lord held court and the servants slept on the floor; the lord's family had chambers in the towers, with fireplaces, latrines emptying down the wall and, by the fourteenth century, glazed windows on the sheltered side. There were kitchens, a chapel, stables, a well, which was the one thing a castle could not do without, storerooms for a year's grain, and a prison in whichever tower was dampest. A castle's garrison in peace might be a dozen men, and a great magnate with twenty castles kept each with a skeleton staff and moved between them with his household, eating his way through the produce of each estate in turn.
The end
Cannon arrived in the fourteenth century and by the fifteenth could bring down a curtain wall in days; the French artillery train of the 1450s took the English castles of Normandy at a rate of one a week. High, thin walls were exactly the wrong shape for resisting a ball, and the response, worked out in Italy around 1500, was the low, thick, angular bastion fort with earth-backed ramparts that absorbed shot, which is a fortress but not a home. The lords kept their castles as houses and status symbols, added windows and gardens, and built new houses without walls at all. The English Civil War was the last time the old castles were fought over, and Parliament slighted most of them afterwards, blowing out a wall so they could not be held again, which is why so many stand as picturesque ruins rather than as buildings.
The takeaway
A medieval castle was a lord's fortified residence and the base from which he held the surrounding land, evolving from Norman earth mounds with timber towers to stone keeps and then to concentric rings of towered curtain wall with fortified gatehouses, designed to make attack slow and expensive. Sieges were mostly blockades helped by trebuchets, towers, rams and mining, and the castle's age ended when cannon could breach its walls, after which fortresses became low and thick and lords moved into houses.