Medieval Warfare in Plymouth

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The first defences of Sutton Pool were probably constructed after 1272 AD in the reign of King Edward I. By this time, England was a relatively stable country and internal warfare between feuding lords had been replaced by external warfare against the French. Plymouth was vulnerable to enemy attack by sea, so the focus was mainly on coastal defence.

Land warfare still involved hand-to-hand fighting by massed ranks of men in mail armour using swords, axes, and pikes. Projectile weapons were in use, crossbows were known to the Romans and by the 12th century they had become common battlefield weapons, while the longbow was used from at least the third century AD, and it was employed by the English as a weapon of war and for hunting. The longbow could fire rapidly and was highly effective at a range of 200 yards (180m), although the arrows could fly much further. By this time, weapons that launched projectiles using a chemical propellant were being developed. The Franciscan monk Roger Bacon wrote about the explosive properties of gunpowder in 1242.  Some 25 years later, the first account in England of artillery that was propelled by gunpowder describes how it was employed by Henry III to quell an uprising in London in 1267, but other authors suggest a later date. A French raiding force attacked Southampton by sea in 1338, and one of their weapons included a single cannon with 48 projectiles.  This cannon was intended to be put on shore and then fired from land.  The Battle of Arnemuiden, fought between England and France in 1338, was the first recorded European naval battle using artillery, where the English ship Christopher was armed with three cannon and one handgun. Early artillery was heavy and difficult to move, so it was initially only useful when attacking fixed enemy defences. Small, hand-held, portable weapons were also developed, which were a precursor to the pistols, muskets and rifles used in later warfare. One example is the arquebus, which was one of the earliest forms of long, hand-held guns that appeared in Europe during the 15th century.

In the twelfth century, curtain wall castles became popular; these had high walls to protect against stone shot launched by trebuchets and had projecting towers so the defenders could fire arrows and other projectiles at an enemy attacking the base of the walls. Initially, the towers were square in section, but the square corners of the towers were a weak point that could be destroyed by undermining and gave the enemy outside the walls somewhere to hide, so later designs used towers that were circular because they were stronger and had no corners for the enemy to hide behind.  The walls could be scaled by the enemy using ladders, so the walls had to be defended.  A walkway was built along the top of the wall where defenders could fire down on the attackers.  A parapet protected the defenders on the top of the curtain wall, and crenelations were cut into the parapet, leaving gaps where archers could fire down on the enemy, interspersed with taller sections of wall that protected the defenders above head height.  Dropping missiles onto the enemy below would expose the defenders to enemy arrows, so the design of the walkway on top of the walls evolved. Pushing the parapet out onto corbels or brackets projecting from the curtain wall left small gaps called machicolations where the defenders could see the enemy below at the foot of the wall. Through these small gaps, the defenders could fire arrows or drop stones, sharpened logs, or incendiaries onto the enemy below.

The castles had a round turret at each corner and perhaps a D-shaped tower projecting outwards somewhere along the length of the wall. The towers were to provide covering fire from above, so they needed to be a minimum distance apart based on how far the defenders’ projectiles could travel.  The tops of the towers also had a walkway, parapet, crenelations and machicolations; they could have a pitched roof or would be flat if used as a gun platform.  The only way to get down from the wall was via stairways built inside the towers, so the towers were heavily defended.  An enemy force that managed to scale the walls and get onto the walkway then had to fight their way into a tower and down the stairs to be able to get into the castle bailey.  Earlier castles included a great keep or donjon (from where we get the word 'dungeon') which was used as the last line of defence in a castle. As high curtain walls evolved, the great keep included in earlier castle designs was not needed, so they went out of fashion, and later castles were built without one. 

The entrance to the castle would always be a weak point, so elaborate gatehouse structures were often built in one curtain wall.  The gatehouse was there to defend the wooden doors to the castle, built up from layers of oak timber bound together with iron straps and rivets to resist battering.  Access to the gatehouse from outside the castle was across a drawbridge or temporary timber ramp that could be removed, and an iron portcullis may be dropped in front of the gates to provide further protection. Gatehouses became elaborate structures with features that allowed the defenders to stop the enemy from reaching the gates, to attack them from a position of safety if they did get that far, or to trap them within the gatehouse between two sets of gates if they managed to break in.  Once trapped, the defenders could fire on the enemy through murder holes built into the walls and ceiling. A ‘back door’ to the castle, called a postern gate or sally port, would be built into the walls to allow the defenders to exit the castle and attack the enemy from behind, or in some cases, to escape.

The enemy could scale the walls using ladders or batter them using siege machines, so castles were sometimes surrounded by a deep ditch or moat to slow the enemy's approach and deprive them of a place to stand next to the wall.  The moat would also deter undermining, particularly when filled with water. To undermine a tower, the enemy military engineers would dig a tunnel from their lines underneath the no-man’s-land between themselves and the castle turret. The ground under the turret could then be excavated away, shored up by baulks of timber.  The timber would be set on fire, causing the turret to collapse, or later, the tunnel would be collapsed using explosives.

The high point of castle design was in the late 13th Century, with the huge and elaborate castles built in Wales by King Edward I.  In later years, conflicts were resolved by pitched battles rather than castle sieges, so castles of this type became obsolete. Only a few castles were built in England in the 14th Century, with a handful constructed to protect the coast against French raiders.

The 14th Century was a time when warfare evolved rapidly once the use of artillery became widespread.  Castles are designed to withstand attack by whatever methods the enemy can deploy, and castle designs evolved in reaction to a continual arms race as new weapons and armour were invented. Defences were still based on castles as strongpoints and high walls surrounding towns, both having proved the most suitable deterrents to attack by invading land armies. Artillery changed all that; suddenly, the castle turret and town wall were vulnerable to an enemy who could knock them down from a safe distance.

If Plymouth Castle was built at the end of the 14th Century, it was constructed when artillery was known, but its full potential was not yet realised.  By the end of the Hundred Years' War, the gunpowder weapon was in widespread use on the battlefield. The early weapons were crudely built, inefficient, and had a comparatively short range and a slow rate of fire. At that time, proof testing of guns before use was more art than science, so the guns could explode in battle and were often as dangerous to the gun crews as the enemy. Development persisted because artillery provided a considerable advantage in warfare, as you could keep your troops safely protected while still inflicting significant damage to the enemy. Artillery provided the means for attacking forces to inflict damage at a distance, and defensive structures evolved to counter this new threat. Artillery became mobile and was used on the battlefield, but still retained a place in fixed structures when used for sea defence. New types of permanent structures were built to defend ports and harbours, used to mount cannon that could fire round stone shot onto enemy ships. Stone curtain walls vulnerable to artillery fire were replaced with earth ramparts that could withstand bombardment from enemy ships, and later, more massive stone-built structures were needed when artillery projectiles became heavier, more efficient, and more accurate.

By the early 16th century, purpose-built artillery forts supplanted the castle’s military function, and the fortified residence evolved into the country house. A strong Tudor monarchy took over responsibility for national defence, leading to the chain of artillery fortifications built by Henry VIII.  The age of the castle was over.

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