by Marc Morris
The trebuchet was a more sophisticated version of the perrier, devised by the Arabs in the course of the twelfth century. Rather than having its throwing arm flipped by men pulling on ropes, it relied on a large counterweight to perform the same function.
There are no surviving originals from the Middle Ages, but we do have pictures and diagrams of trebuchets in medieval manuscripts. Using this information, a team of historians end engineers has built a replica at Caerphilly Castle in Wales. Like a crossbow, the trebuchet is a machine which works on the principle of stored energy. The first part of the process involves heaving the counterweight – a wooden box filled with around two tons of earth and rocks – up and into place. A team of four or five men pulling on ropes can do this in about five minutes. Once the weight is raised and secured in place, the machine can be loaded. The missile – here a ball of cast concrete, but originally made of stone or lead – is then placed in the end of a sling attached to the long end of the throwing arm. When all is ready, a sharp pull on the trigger causes the counterweight to drop, pulling the short end of the arm downwards with tremendous force, hurling the long end upwards, and pulling the rope-sling after it.
A perrier.
The whole motion, difficult to describe, is extremely elegant to watch; it looks like a cricket ball being bowled overarm. The surprising thing is the noise – or rather, the lack of it. Instead of the explosive charge of a cannon, and the whistling of the missile, there is just a scrape as the ball moves from under the frame, a shudder as the arm is stopped in its spin, and then – nothing. The ball moves through the air in total silence. It’s like watching a film with the sound turned off. The effect is utterly captivating: the motion of the machine and the arc that the missile describes are both exceedingly graceful.
The replica trebuchet at Caerphilly. The counterweight (within the frame) is raised by pulling the arm at one end and winching at the other.
The Caerphilly trebuchet, it must be said, is an impressive beast. With a twenty foot-long throwing arm, it is a ‘full-sized’ replica, and its twenty-five-pound missiles would cause serious damage if directed against buildings (at Caerphilly, they splash down into the moat). It would have been quite possible, however, for medieval engineers to build much larger trebuchets – monster machines more than twice the size, with throwing arms up to fifty feet long. Very little could stand in the way of such huge weapons. Wooden buildings in a castle’s bailey would be smashed to smithereens. Lead roofs would offer no resistance. The only thing that might withstand a direct hit was masonry. Whether or not it did so would depend on a number of factors – how close the attacker dared to bring his engines, how large the machines were, and how heavy the missiles. It would also depend on the skill of the engineer and the precision of his catapult, since to bring down solid stonework would in most cases require several hits in the same place. Above all, it would depend on one question: how thick and well built were the walls?
The men inside Rochester Castle were now asking themselves much the same thing: would the walls of the tower, twelve feet thick, hold out against King John’s trebuchets? The Barnwell Annalist says that the bombardment of the keep did not cease by day or night. There is no suggestion, either from Barnwell or from any of the chroniclers, that the defenders were subjected to the kind of psychological and biological horrors we often hear about in other sieges. Sometimes rotting animal carcasses or the heads of fallen comrades were hurled over the walls of a besieged city or castle, in an attempt to spread plague and terror. John may not have resorted to such tactics (though one would hardly put it past him), but he knew, in any case, that the relentless barrage was piling psychological pressure on his enemies. As the stones rained down on them, as their food ran short, and as the winter cold began to set in, surely they could not hold out much longer?
And yet they did. Part of the reason for the rebels’ dogged determination was an earnest belief that the cavalry would arrive – either in the shape of Prince Louis, or in the more likely form of their London associates. According to one chronicler, the knights who remained in the capital had sworn to Albini and his colleagues that, should Rochester be besieged, they would ride to their aid. Up to a point, they kept their promise. Two weeks into the siege, a force of seven hundred horsemen left London and headed towards Rochester. Halfway there, however, their nerve failed; at Dartford, they turned and headed back. Why they did this is unclear, but it is possible that their scouts had returned with news of the size of the John’s army. We don’t know how large the king’s force was, but we can get some idea from the fact that seven hundred fully armed knights turned in fear and fled.
John would have learned soon enough that his other enemies had retreated back into their hole, and the news must have gladdened him somewhat. It was only a small consolation, however, because the fact remained that Rochester Castle and its defenders were still holding out, despite everything his expensive siege engines could throw at them. With every day that passed, it was becoming increasingly, maddeningly clear that the trebuchets were not going to work. The king, therefore, placed all his faith in his last remaining option: to drive a mine under the great tower, in the hope of bringing it crashing to the ground.
The technique of undermining was not a new one; the Romans and the Vikings are known to have used mines when laying siege to cities. The aim was to drive one or more tunnels under the foundations of the walls, supporting the ground above with timber props, which were then burnt away to create a collapse. But this wasn’t always possible. If the defences were built on solid rock, tunnelling underneath them was virtually impossible. Water defences, or even just soft or waterlogged ground, also meant that mining was out of the question. And even if the conditions for mining were ideal, conditions for miners themselves were anything but. The environment in which such men worked was dark, damp and dangerous: the process could easily end in disaster if the soil above them suddenly subsided.
Digging a mine in peaceful circumstances was difficult enough, but doing so during a siege was doubly dangerous, since the besieged would do everything in their power to frustrate the miners’ progress. Just getting close enough to begin digging would involve dodging a shower of arrows and crossbow bolts, so miners took care to approach under the cover of a ‘tortoise’ or ‘cat’ – a wooden canopy, moved on wheels, and covered in damp animal hides to prevent it being set on fire. Even once they were underground, the miners were still in danger of attack. Roman writers speak of defenders flooding enemy mines and drowning their assailants. A more common approach was for the defenders to dig a counter-mine, either in the hope of causing a collapse, or simply with the intention of meeting their opponents head on, and engaging them in subterranean hand-to-hand combat.
Luckily for John, his engineers reported that the ground around Rochester was suitable for mining. Even so, it was far from being an easy task. Despite having at their disposal all the picks that the men of Canterbury could manufacture, the operation was set to take weeks. At one point, progress ground to a halt when the miners came up against solid stone foundations – not those of the keep or the bailey walls, but the old Roman walls of Rochester. Only by making a detour could they continue with their tunnelling.
For the defenders trapped inside the keep, it was an agonizing waiting game. There is no indication that they tried any of the advanced techniques of counter-attack above, beyond of course trying to pick off miners with crossbows when they emerged from tunnelling. As with the trebuchets, they could only pin their hopes on the solidity of the tower and its foundations. These, we know, were profound; excavations in the late nineteenth century failed to find the bottom of the walls. Getting right underneath the keep must have been a hellish task.
Finally, however, John’s miners managed it. By 25 November, the mine was ready. Hundreds of tons of masonry were now supported only by wooden pit props. On the same day, John sent a letter to his trusted servant, Sir Hubert de Burgh. ‘We order you,’ he said, ‘to send us forty bacon
pigs.’ This was not, however, the makings of a thank-you dinner for the hardworking miners – even a glutton like John would have struggled to finish that many ham sandwiches. The kind of pigs the king wanted, he went on to specify, were ‘the fattest and least good for eating’. It was not food that John was after, but fuel. The unfortunate animals were needed ‘to set fire to the stuff which we have put under the tower at Rochester’.
Once the mine was finished, it would have been stuffed with brushwood, straw and kindling to feed a great fire. How the pig fat was introduced is a matter of debate. An older generation of more imaginative historians envisaged the forty-strong herd being driven into the tunnels while still alive, burning torches tied to their tails. Sadly, modern military experts now think this unlikely; the idea of live pigs running around with firebrands attached is just too farcical, even for King John. It is now believed that the pigs were slaughtered and rendered down for their fat, which was subsequently poured into barrels and rolled into the mine.
With or without an accompaniment of squealing pigs, the scene that followed must have been both horrifying and spectacular. Torches were introduced to the tunnels. Deep underground, the kindling caught and the pig fat crackled. Flames started to lick the fatty wooden props and, as the fire grew to a roar, the props started to snap. Suddenly, the ground above the mine fell away. The great keep shuddered and split. With a final deafening roar, a quarter of the building came crashing to the ground.
The dust had hardly settled before John’s men were pouring into the keep through the gaping hole. Amazingly, in spite of the terror and confusion that the collapse must have caused, the men inside fought on. The south-east corner of the keep had been reduced to rubble, but its great cross-wall remained standing; using this, the rebels mounted a last, desperate line of defence. It was successful: try as they might, the king’s men were still unable to force their way in.
At the start of the siege, John had openly derided his opponents’ stamina.
‘I know them too well,’ he allegedly spat. ‘They are nothing to be accounted of, or feared.’
Having now spent seven weeks besieging them, the king must have felt like eating his words.
In the end, despite all John’s military ingenuity, it was starvation that finally forced the rebels to surrender. By this stage the men in the keep were totally out of supplies, and had been reduced to living on the flesh of their own expensive war-horses. This, says the Barnwell Annalist, ‘was a hard diet for those who were normally used to fine food’. At first the defenders tried to cut their losses by sending out ‘those who seemed the least warlike’: perhaps those too exhausted to fight, or possibly non-military personnel, such as clerics or blacksmiths. John, however, was in no mood for such half-measures. When these men emerged he had them mutilated, lobbing off their hands and feet in an effort to persuade those still inside to surrender. Eventually, lacking the strength to fight on any longer, the remaining rebels gave themselves up. By curious coincidence, it was 30 November – the feast of St Andrew, Rochester’s patron saint. The struggle for the city’s castle had lasted for the best part of two months.
‘Living memory does not recall,’ concluded the Barnwell Annalist, ‘a siege so fiercely pressed, and so staunchly resisted.’
After such a long, costly and bitter struggle, John was apparently in no mind to be merciful. According to one of the chroniclers, the king intended to celebrate his victory by having every member of the rebel garrison hanged. This would not have been entirely out of character – the king was famous for gloating when he had the upper hand. However, according to the same writer, one of John’s foreign captains persuaded him to show clemency in the name of self-interest. The war, he argued, was not yet over. What if John or his allies were themselves captured at some later stage? Better the king should imprison his enemies, rather than start a round of tit-for-tat killing that might end up with his own neck in a noose.
It is doubtful that John really needed to have the logic of this argument explained to him by one of his own men. Showing mercy towards a defeated opponent was perfectly normal behaviour in the early thirteenth century. Ever since 1066, warfare in England had been regulated by the code of chivalry. In John’s day, this had nothing to do with later perversions like laying your cloak over a puddle, or letting your enemy strike the first blow. It meant, in essence, that political killing was taboo. Naturally, this did not apply to the non-noble members of society. John had already demonstrated as much when he ordered the mutilation of the ‘less-than-warlike’ members of Rochester’s garrison during the final stages of the siege. After the surrender, he proved the point a second time by hanging one of the rebel crossbowmen (apparently punished for his treachery – the lowborn bowman had been raised in John’s household). Chivalry was not about a high regard for human life in general; it was a code that condemned killing among the upper classes, based on exactly the kind of enlightened self-interest advocated by John’s foreign captain.
Chivalric self-interest, moreover, extended beyond insuring against future reprisals. The man who spared his noble opponents stood to make a significant profit in the form of ransoms. Prisoners were valuable assets, as John fully appreciated. When the rebels were being clapped into chains, the king personally confiscated the most important ones for himself. For example, William de Albini was despatched to the king’s castle at Corfe, and ended up with a price on his head of £4,000. Having appropriated the choicest prisoners in this manner, John generously distributed the less important individuals among his cronies as gifts.
For the rebels themselves, the defeat at Rochester was a massive blow to their cause, and it left the remaining barons in London feeling totally discouraged. The Barnwell Annalist, concluding his section on the siege of Rochester, commented that ‘there were few who would put their trust in castles’, and he was absolutely right. When John moved into East Anglia at the start of 1216, the castles of Colchester, Framlingham and Hedingham fell in quick succession. All three were mighty stone castles, and before Rochester, men might have hoped to defend them. After the great siege of that autumn, there was no longer the will to do so.
John, however, despite scoring these new successes, never managed to pluck up the courage to risk a decisive assault on London. His delay cost him dearly. In May 1216, a full year after the rebellion had flared up, Prince Louis landed in Kent and quickly gained control of south-eastern England. All the castles that had fallen to John were suddenly back in the hands of his enemies. Only those fortresses which the king had placed in the hands of his closest servants held out for him. Hubert de Burgh – the man who came through with the pigs – successfully defended the great castle at Dover against the French assault.
By the autumn of 1216, the war was deadlocked. John held sway in the Midlands, but the south and east remained in the hands of his opponents. Ultimately, the situation was resolved by the king’s over-exertion and overindulgence. In early October, after a really good dinner with the burgesses of King’s Lynn, John fell sick with dysentery. He struggled on for a few days, time enough to reach the castle at Newark. By the time he got there, however, it was plain to everyone that he was dying. In the small hours of the morning on 18 October, as a gale howled around the castle walls, the king finally gave up the ghost.
The rebuilt corner of Rochester’s keep.
Since the cause of the war had been John himself – his bad governance, his untrusting personality, and his broken promises – the king’s death removed most of the reasons for fighting. It was much more difficult for the die-hard rebels to justify their opposition to John’s blameless nine-year old son, now crowned as King Henry III. Moreover, the new king’s governors encouraged a cease-fire by recognizing the legitimacy of many of the rebels’ grievances. They issued a new version of Magna Carta, and indicated that in future the king would respect its terms. The only person who stood to lose out now was Prince Louis; it took a decisive battle at Lincoln and a large payment of cash to persuade him to go
home.
By 1217, the war was over; John was dead and peace had been restored. Rochester Castle, however, remained shattered and broken – a pale reflection of its former glorious self. It was not until ten years later that builders arrived to make good the damage. The work they carried out was not a reconstruction, but a repair job. Inside the castle, the new archways look shabby in comparison with the elegant originals. Outside, the contrast is even more striking. The collapsed corner of the keep was rebuilt, not with a square tower as before, but with a round one. This had nothing to do with aesthetics; the repairs make a real mess of what was previously a very handsome building. But the king’s masons weren’t interested in making the castle look pretty, or putting it back together piece by piece. The recent siege had demonstrated, in the most dramatic way imaginable, that great towers – even the greatest towers – were vulnerable. Masons, however, had already thought of ways to make castles stronger.
CHAPTER THREE
BUILDING AN EMPIRE
CAERNARFON IS ONE of my favourite castles in the UK. It sits right beside the sea on the coast of north Wales, opposite the island of Anglesey, surrounded by swans and besieged by seagulls. Despite its remote location, the castle is familiar to millions of people because of the spectacular ceremony that took place there in 1969 – the investiture of Prince Charles as Prince of Wales.
It was, for many reasons, the perfect place for such an occasion, not least because of its stadium-like proportions. For centuries, poets and painters had come to Caernarfon and gazed in wonder at this giant among castles. In his diary of 1774, Dr Samuel Johnson described it as ‘an edifice of stupendous majesty and strength’.
