The Use of Mining in Sieges early-13th Century England

Techniques of siege.


Rochester saw one of the few military successes of King John. Rochester 1215, illustration by John Cann.

King John uses mining to win this famous siege

Known to history as `Bad’ King John, the infamous English monarch has gained a reputation for military incompetence, but during the Siege of Rochester Castle he demonstrated a little-known talent for siege warfare. Rebel barons defended the fortress and the siege lasted for two months before surrendering to John. The ­ fighting was ­ fierce and without letup, with the Barnswell Chronicler recording, “Our age has not known a siege so hard-pressed nor so strongly resisted.”

John committed himself totally to retaking the castle and set up his command post on Boley Hill. When his siege engines failed to make an impact on the strong walls, he ordered mining tools to be delivered. On 25 November 1215, he sent an urgent writ to his justiciar to, “Send us with all speed by day and night, forty of the fattest pigs of the sort least good for eating, to bring ­ re beneath the tower.” This meant a mining operation. Pig fat was used to ­ re the mine props that John had positioned beneath the southeast corner of Rochester’s keep, which in turn kept up the undermined foundations. The king’s mine was successful and a whole section of the keep came down, but despite this achievement the rebels retreated further inside the keep and the siege continued. After they were reduced to a diet of horse-flesh and water, the garrison eventually surrendered to John.

Rebel Scum

Throughout this period of conflict in England, the barons looked across the Channel to the powerful and stable royal line in France. In marked contrast to the discontent, conflict and usurpations which had characterised the Anglo-Norman monarchy since 1066 (Gerald of Wales notes that the Plantagenets were `princes who did not succeed one another in regular hereditary order but rather acquired violent domination through an inversion of order by killing and slaughtering their own’), the French had experienced over two hundred years of smooth successions from father to son. Philip Augustus had been on the throne for thirty-five years, and his five immediate predecessors had enjoyed reigns of between twenty-nine and forty-eight years each. He had an adult son, a younger son and two grandsons. The barons might be understandably wary of offering the throne to Philip himself (and besides, he was now fifty years old so possibly not a long-term prospect), but Louis was a younger man, a proven warrior, a prince with a reputation for being moral and just; he came from a dynasty which had a tradition of involving a council of nobles in its decision-making process; he had a claim via the blood of his wife, John’s niece. And on a more practical level, with the might and resources of the French crown behind him, he was likely to be successful. This tipped the balance in his favour against other possible candidates such as King Alexander of Scotland (who was descended from the old Anglo-Saxon kings of England) who did not have the military might to back up a potential claim. And Louis being French had an additional advantage: many of John’s mercenaries were from various regions of France, so having Louis at the head of the campaign might mean that John would be deprived of their services, as he had been in Poitou in 1214. Of further comfort to the barons was the fact that Louis, if and when he became king, would probably not reside in England permanently, thus giving them more scope for their own activities. This was not unusual as Henry II and his predecessors had spent much of their time on the Continent, so there was precedent for a cross-Channel king. All in all, he was the perfect choice. A party of barons headed by Saer de Quincy, the earl of Winchester, Henry de Bohun, the earl of Hereford, and Robert Fitzwalter sailed for France in September 1215.

September was the month in which John was expecting the arrival of the new mercenaries he had engaged from Aquitaine and Flanders; he headed to the Kent coast in anticipation. However, there were storms and heavy seas during that month and instead of the expected ships, waves of drowned corpses washed up on the shores along Kent and Suffolk.

While John was bemoaning his losses on the coast the barons decided to take advantage of his situation by capturing Rochester Castle, which would bar his route back to London. The castellan there had been loyal to John for many years but, perhaps seeing the writing on the wall, he opened the gates to the rebels. This irritated John, who moved to assault it; there would now be actual armed conflict on English soil between the king and his subjects. A line had been crossed.

The barons had garrisoned Rochester well: ninety-five knights and forty-five sergeants held it under the leadership of William d’Albini, an able commander. However, as they expected Rochester to hold until the delegation returned from France they had made no back-up plans for reinforcing it and had no second force ready to relieve a siege. John, on the other hand, was prepared for the long haul. He had siege machinery built and remained at Rochester for seven weeks, conducting the operations personally – the longest he had ever spent in one place since his accession to the throne sixteen years earlier. Roger of Wendover tells us: `The siege was prolonged many days owing to the great bravery and boldness of the besieged, who hurled stone for stone, weapon for weapon, from the walls and ramparts on the enemy.’ The keep resisted all attempts at assault so John turned to mining: a tunnel was dug under the wall, held up by wooden posts, then filled with flammable material including the fat of forty pigs which John sent for specially, and set alight. As the timbers burned and collapsed the roof of the mine caved in, bringing one of the four towers of the keep crashing down. The garrison, by this point starving and forced to eat their horses, retreated to the other half of the keep and resisted a little longer but eventually realised it could not hold out and surrendered on 30 November 1215. John’s first inclination was to execute them all, but he was persuaded not to on the basis that similar treatment would then be meted out to royal garrisons by the barons. In the end only one man was hanged, a crossbowman who had previously been in John’s service.


Dover siege reconstruction by Peter Dunn.
Dover Castle siege, 1216, (c1990-2010). Reconstruction drawing of a French siege tower and earth works. Commanding the shortest sea crossing between England and the Continent, Dover Castle was a vital strategic and communication lynch-pin in the empire of the Angevin kings of England. in 1216, The castle successfully resisted a major siege directed personally by Prince Louis of France during his near-successful invasion of England. He had some success breaching the walls, but was unable ultimately to take the castle. Artist Peter Dunn. (Photo by English Heritage/Heritage Images/Getty Images)
Dover Castle, Kent. The siege of 1216. Reconstruction drawing by Peter Dunn (English Heritage Graphics Team) of mining under the North Gate East tower…

The future Louis VIII of France fought a forgotten war for the English crown against John I and Henry III.

A prince of France uses mining as part of an attempted invasion of England.

The Siege of Dover Castle was part of a military campaign by Prince Louis of France to assert control over England. King John had alienated many of his nobles and some of them invited Prince Louis, the son of the King of France, to invade England and rid the country of John’s tyranny. Louis tried to take the strategically vital fortress at Dover to secure the conquest of Kent.

The siege began in July 1216. He used trebuchets, mangonels and siege towers to try and take the castle but then resorted to mining. A Cat was used to protect the miners and Dover’s timber barbican was undermined, enabling Louis’ men to successfully storm the barbican. Louis now tried to press his attack and sent miners to dig beneath the main castle gate. A chronicler recorded, “They mined, so that one of the towers fell, of which there were two.”

Large numbers of Louis’ men managed to enter the castle through this breach but the defenders, who successfully blocked the gap in the defences with timbers, repulsed them. After this failure Louis was forced to strike a truce and he eventually had to abandon the siege and ultimately left England. Dover showed that the potential of siege mining was limited and in this particular case in­fluenced the failure of a determined invasion of England by a foreign power.


Mining was a subterranean response to end a siege if conventional weapons, such as mangonels, battering rams and trebuchets, failed to make an impression on the walls. Towers and keeps were particularly hard to destroy by conventional means, so miners would dig beneath them in order to weaken their foundations. Miners had a very dangerous job, as their digging efforts would initially be in plain sight of the garrison and to begin with they had to rely on the protection of a `Cat’.

The Cat was a covered house placed on wheels with a very strong roof. The besieged garrison would always try to destroy this device, so the Cat was designed to withstand assaults from weapons as varied as heavy stones, beams of wood, hot water, molten lead and spiked poles. Under this portable cover the attacking force would dig beneath the walls. While they worked, the miners would build wooden supports to prop up the tunnel and once they were sure they had dug far enough, brush would be mixed with pig fat and placed near the wooden supports. When all of the ­ flammable material had been placed in the mine, everybody would evacuate the tunnel except for the torchman who would set the place on ‑ fire, before also hurriedly departing. As the wooden supports burned, they would collapse and in theory the stonewalls or towers would collapse with them.

The digging and preparations were hazardous in themselves but miners were also at risk from prematurely collapsing tunnels and counter-mining activities from the enemy garrison. Defending armies attempted to detect miners by using buckets of water in suspected digging areas. When a potential mine was detected, garrisons would start digging their own tunnels to counter the miners’ efforts. If these passageways ever connected then ‑ fierce hand-to-hand ‑ fighting would often ensue, which was especially dangerous in the weakly supported tunnels. Siege mining was definitely not for the faint-hearted.

The Siege

Louis arrived in front of Dover Castle on 25 July 1216. It was an impressive sight and a daunting prospect: huge and well-fortified, it had been much enlarged and improved by Henry II and now comprised a stone keep – 100 feet (30 metres) square and with walls up to 20 feet (6 metres) thick – in its own compound, surrounded by curtain walls broken only by a great twin-towered gatehouse at the north-western tip of the castle enclosure, which was itself protected by a wooden barbican, an additional defensible structure erected in front of it. Inside, Hubert de Burgh had some 140 knights (many of them Flemish or Poitevin), a greater number of sergeants, plenty of weapons and an ample store of supplies. The castle was set high on a hill overlooking the town, which gave the defenders even more of an advantage. To capture it would take a huge investment of time, troops and resources.

Thanks to a remarkably detailed and almost certainly eyewitness account in the History of the Dukes, we are very well informed about the progress of the siege of Dover. When Louis arrived he spent several days with his army billeted in or camping around the town, reconnoitring and planning. Louis accommodated himself in a priory rather than in the tented encampment; he needed a campaign headquarters, and he no doubt thought that he might as well lodge in some comfort as nobody was going anywhere for a while. Then he divided his forces, one part remaining in the town to one side of the fortress and the other moving to the hill in front of the castle gatehouse, which gave him the advantage of higher ground and from where he was able to direct siege operations. Petraries and mangonels were set up to bombard the walls and the gate, but the machines which had succeeded at Winchester and Odiham would be insufficient at Dover.

Before he had set off for the coast Louis had sent a messenger back to France to ask his father for help, and this help duly arrived in the shape of large-scale siege machinery. Philip sent over a device known as Malvoisin or `Evil Neighbour’, which was probably the first appearance of a trebuchet on English soil. A trebuchet acted in a similar way to a petrary, in that it used balance in order to throw stones. However, instead of using traction – men pulling down on ropes in order to fling the other arm of the lever in the air – it used a counterweight. A long wooden beam was pivoted near to one end; the longer side of the beam ended in a sling, in which the projectile was placed, and the shorter end held a large weight, generally a container filled with earth or rocks. A team of men would haul down the sling end in order to lift the counterweight into the air, at which point the beam was fixed and held in place. A stone or other missile was loaded into the sling, and then the beam was released: the counterweight came crashing down and the missile was flung into the air. The advantage of the heavy counterweight was that the trebuchet could throw much bigger stones over a much greater distance than either traction or torsion machines.

Despite what must have been his satisfaction with his new engine of war, Louis did not rely on this alone. His troops were already blockading the landward side of the castle; now his ships, after unloading their cargo, secured the sea outside Dover so the castle was completely cut off from outside aid and could not be either reinforced or reprovisioned.

Louis’s first point of attack was the gatehouse and barbican to the north of the castle enclosure. As well as his stone-throwing machinery he also had his men build a wattle siege-tower (a device which put the besiegers on the same level as the defenders on the wall, meaning they could shoot arrows across at them; alternatively it could be filled with men and then moved closer to the wall, so the besiegers would not need to try and scale it by ladder, which left them open to attack or bombardment from above) and he also set men, under cover of a protective moveable device known as a `cat’, to undermine the walls. As had been demonstrated at Rochester the previous year, mining was an effective strategy, but it was a very slow process as the attackers were only able to use pickaxes and other hand tools against the gigantic stones and their foundations.

The siege was by no means one-sided. While Louis was directing these operations from the field north of the castle, the garrison made frequent sorties, charging out on horseback to kill and wound the attackers in hand-to-hand combat. Louis’s men repulsed them but were unable to inflict many casualties in return as the defenders could retreat back behind their walls. Those inside were also able to use their crossbowmen as snipers, picking off anyone foolish enough to bring himself into range without adequate protection. Louis, who had no doubt been told in his youth of the agonising end of Richard the Lionheart from blood poisoning following a wound inflicted by a crossbow at a siege, was not harmed, although he probably wore his mail armour almost permanently.

The weeks went by, and gradually men began to trickle away from Louis’s force. The count of Holland had taken the cross and now decided that the time was right for his pilgrimage to the Holy Land; some knights felt that their obligatory period of military service was up; some mercenaries thought they were not being paid enough; others were killed by the frequent sorties of the defenders. Committed to staying in one place, Louis for the first time began to lose the initiative in the war, and with it his temper. Roger of Wendover notes that he was `greatly enraged and swore he would not leave the place until the castle was taken and all the garrison hung’.

In the middle of August there was a breakthrough when Louis’s knights made a direct and bloody attack on the barbican which protected the main gate, and were able to capture it; the History of the Dukes tells us that Peter de Craon, who had defended the barbican so well for many weeks, was killed in the attack along with other men. However, although the besiegers were one step closer they were still confronted with the double-towered gatehouse; and, even if they could batter their way through that, the defenders could regroup further by taking refuge in the keep. A long campaign was still on the cards.

Louis continued with the siege, and was heartened by further reinforcements from France: Peter de Dreux, who had left his obligations in Brittany in order to come to the aid of his cousin and companion, and Thomas, the young count of Perche. Perche was a rising star of the French nobility: he had succeeded to his title in 1202 at the age of seven after the death of his father, had fought for King Philip at Bouvines while still in his teens, and now at twenty-one was building a reputation for deeds of arms and chivalry. In an example of how inextricably the men on both sides of the conflict were linked, Perche was a kinsman of John’s most faithful supporter, William Marshal (his great-grandmother and Marshal’s mother were sisters); he also had a tenuous claim to the English throne himself as his maternal grandmother was John’s sister Matilda, but he supported Louis wholeheartedly.

Both nobles had brought knights and men with them, which would help the cause, but the news also came across the Channel that the new pope, Honorius, had confirmed Louis’s sentence of excommunication. It was a bitter blow, but Louis was by now in far too deep to back out from claiming the crown of England even if he had been so inclined. He would push on: once he had subdued the country, captured John and been crowned he would have the leisure to talk properly to the pope, not to mention the power to influence him.

In the meantime, as August turned into September, Dover still needed to be subdued. The miners had been continuing their slow and painstaking work, and now came the breakthrough: one of the towers of the gatehouse was brought crashing down, and Louis and his knights could charge into the breach.

This is what the knights had been waiting for. Trained since boyhood to engage in hand-to-hand combat, they detested having to kick their heels at a siege while miners and engineers held sway. Now they had the chance to throw themselves at the enemy in person, to take out their frustration at the long siege, to hack with their swords and their axes into armour and flesh. But the defenders were just as frustrated, just as fierce, and even more desperate – after all, had Louis not threatened to hang them all once the castle was taken? The normal policy at the time was that if a garrison surrendered they would be allowed to leave unharmed, but that if a castle had to be taken by storm then those inside were liable to be executed. After irritating Louis and thwarting his plans for so many weeks they were unlikely to be treated with clemency if defeated, so they fought back with all their might, filling the gap in the wall with men. Slowly but surely they repulsed the attack, holding the line, pushing the besiegers back and keeping them out long enough for running repairs to be made to the breach, which was shored up with timbers taken from buildings inside the compound. The barricade held. Dover still stood.

The stalemate could not be allowed to go on forever. Force had not worked; starving the garrison out would take too long and Louis needed to be on the move. To stand still for too long, as he well knew, was to lose momentum. Louis agreed a truce with Hubert de Burgh, and his army withdrew from the siege on 14 October 1216.


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