Motte and bailey c. 1050–1100
An earth mound with a timber tower, and a fenced yard below it.
I · c. 1050–1100
Motte and bailey
An earth mound with a timber tower, and a fenced yard below it.
The first castle on our hill is made of earth and wood. Labourers dig a ring ditch and heap the spoil into a steep mound, the motte, crowned with a timber tower and a palisade of sharpened logs. Beside it, a larger enclosure, the bailey, is ringed by its own ditch, bank and fence, with halls, stables and stores inside.
Such castles could be thrown up in weeks by forced labour, which made them ideal for an invading army holding down a conquered country, as the Normans did in England after 1066. Their weakness was fire: timber burns, and rots within a generation.
It answered: It answered raids and local revolt: a small garrison could hold off an angry crowd or a band of mounted warriors.
To see one: Pickering Castle, England (motte later rebuilt in stone)
II · c. 1100–1180
Stone keep
A massive square stone tower inside a stone curtain wall.
As the land settles, the timber gives way to stone. A great rectangular keep rises, its walls several metres thick, with the entrance at first-floor level up an outer stair. The palisade is replaced by a stone curtain wall with a simple gate tower, and the bailey fills with stone buildings.
The keep is both home and fortress: the lord's hall, chamber and chapel are inside, and its sheer bulk tells everyone who rules here. Defence is passive. The walls are meant to be too thick to break and too high to climb, but the square corners and the blind ground at the foot of the wall can be attacked by miners.
It answered: It answered fire and the battering ram: stone does not burn, and the walls were too thick to break with simple tools.
To see one: Rochester Castle, England
III · c. 1190–1260
Flanking towers
A curtain wall studded with projecting round towers and a twin-towered gatehouse.
Crusaders and masons had seen the great walls of the East, and the idea of flanking fire spread. On our hill, round and D-shaped towers are now built out from the curtain, so archers can shoot along the face of the wall at anyone attacking its foot. The weak gate becomes a strong gatehouse between two towers, with portcullises and murder-holes.
The keep loses its central place. Round towers have no corners for miners to target, arrow-slits multiply, and the wall top gains wooden hoardings in wartime. The whole circuit, not one tower, is now the defence.
It answered: It answered mining and the counterweight trebuchet: flanking towers covered the foot of the wall, and rounded faces deflected stones.
To see one: Framlingham Castle, England (early square towers); Beeston Castle, England (D-shaped towers)
IV · c. 1270–1300
Concentric castle
Two rings of walls, the inner higher than the outer, so both can shoot at once.
At its peak, the castle on our hill becomes two castles, one inside the other. A low outer wall runs close around a tall inner wall with great towers. Defenders on the inner wall can shoot over the heads of those on the outer one, so an attacker faces two layers of fire at once. If the outer ring falls, the enemy is trapped in a narrow killing ground between the two.
Gatehouses are offset so no straight line runs through, and the lord's rooms move into the main gatehouse. These castles were extremely expensive, and only kings and the richest lords could build them.
It answered: It answered the full siege train of the 13th century: engines, towers, mines and assault together met defence in depth.
To see one: Beaumaris Castle, Wales
V · c. 1400–1500
Adapting to cannon
Walls are thickened and lowered, towers cut down, gunports opened and earth banks piled behind.
Cannon change the problem. A tall, thin wall that defied a trebuchet now cracks under repeated shot. On our hill the old towers are cut down and filled solid, walls are thickened and backed with packed earth that soaks up the impact, and low, round artillery towers are added at the corners.
Arrow-slits are widened into round-bottomed gunports for the castle's own guns, and outworks of earth and timber are thrown up in front of the gate. The castle still looks medieval, but it is becoming a gun platform.
It answered: It answered the bombard: lower, thicker, earth-backed walls absorbed shot, and the castle's own guns fought back.
To see one: Ravenscraig Castle, Scotland
VI · c. 1530–1700
Bastion fort
A low star-shaped fort of angled bastions, earth ramparts and outworks: the trace italienne.
Finally the old castle is swept away. Engineers trained in the Italian method lay out a low fortress whose plan looks like a star. Each corner is an arrow-shaped bastion, angled so guns on its flanks can sweep the face of the next bastion and the ditch below, leaving no blind spots. The ramparts are thick earth faced with stone, and a gentle slope, the glacis, hides them from enemy guns.
In front of the ditch stand triangular ravelins and other outworks. Attackers must now dig zigzag trenches forward for weeks, a slow science of its own.
It answered: It answered siege artillery on wheels: low, angled earth ramparts deflected shot, and every face was covered by cannon.
To see one: Fort de Bourtange, Netherlands