It is great to have a castle, or large fortress, to set a scene in a historical novel.  The high curtain walls, the gatehouses, the murder holes and cunningly placed arrow slits.  All give the writer great scope in describing formidable bastions that appear all but impossible to penetrate.  However, history teaches us that the appearance of impregnability can be illusory, as ever since people started building walls to protect their buildings, others have been devising ways to get in – by fair means or foul.

Ancient siege weapons – the Greek Catapult.

When I started writing my first novel on Alexander the Great, I spent plenty of time researching the early catapults that Alexander used in besieging the many cities of Persia, in his conquest of the Persian Empire.  I proudly presented a long chapter to my father (who was helping me edit the novel) which held long explanations of the mechanics of the engines, describing them in great detail.  My father promptly put great red crosses through all the pages and scribbled “Too much information!!”

It was a great lesson for me as a writer, and taught me that historical detail should always be added subtly to novels, and not forced upon the reader in an endeavour to cram all the writer’s knowledge into the work.  When writing a historical novel, it is paramount to remember you are a writer first and foremost, and not a teacher.

However, my clumsy attempt to give prominence to these weapons wasn’t without reason.  When we think of Alexander the Great today, we tend to think of his vast land battles in which he led his Macedonian army so courageously, such as  Issus or Gaugamela.  But in his day, what Alexander was most famous for, was storming walls, and taking fortified cities.  The reason for this was Alexander the Great was the first man to truly achieve this repeatedly.  Up until Alexander came along, the chances were if you built a thick enough wall around your city, you’d probably be safe.  Alexander changed the rules, and warfare would never be the same again.  Alexander used a variety of rams, and covered siege towers, that he used to directly assault walls, but normally he’d weaken them first, using the latest technology of the day – the catapult.

A few hundred years earlier, the Phoenicians had devised the first great composite bows that could fire bolts much larger than your normal bow and arrow.  The composite bows would be made from two materials, one that was very difficult to compress, such as horn, and the other half something that was very springy, like yew.  The horn would be bound to the inside of the yew, and together they would make an incredibly powerful bow that could be drawn with the help of a lever.

However, by the fourth century BC, and the time of Alexander, this technology had moved on with the torsion engine.  A thick cable of sinew was wrapped around a lever and repeatedly twisted, building up a great amount of energy before being released without breaking.

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This combined with the composite bow, made for a very powerful machine that could shoot either bolts or rocks, which were flung at the walls and could reduce all but the strongest walls to rubble.

 

Roman

When the Romans brought the Greek states into their Empire via conquest, they also inherited the Hellenic torsion technology and like most things they came across, they developed and improved it.  The Roman Ballista was one such machine that was powered by two horizontal arms which had been inserted into two springs of sinew that were tightly wound by the use of a winch.  These came in a verity of sizes, the smallest used to hurl rocks or bolts over the city walls, whilst the largest could hurl projectiles that weighed three talents (approx. 80 kg or 175 pounds) and be able to destroy most obstacles that lay in its path.

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They also developed other uses of the torsion technology such as the Onager that’s kicking action resembled the wild ass it was named after, and the self-loading Polybolos that could fire a succession of smaller bolts repeatedly.

After being assailed by such weapons, the opposing city or fort could normally be forced into surrender, but if necessary the Romans were prepared to assault the walls themselves with a variety of Rams.

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Medieval

After the Roman Empire fell, and the world slipped into the dark ages, most of this technology was forgotten for a time, and clever siege engines and sophisticated catapults disappear from history for several centuries.  Competing Kings would prefer to put their faith in god, rather than rely on technological solutions.

However, with the onset of the medieval age, and the upsurge in Castle building and formidable thick walls, something more tangible than blind faith was needed to prise them open.  Small scale catapults or ballistae were no longer going to cut it, for this you’d need something larger – much larger…

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The Medieval Trebuchet.

The concept of the Trebuchet is actually very simple, a large counterweight is attached at the end of a long lever.  Attached to the long lever, is a sling, so when the counterweight is allowed to fall, the energy is transmitted into the end of the throwing arm and the projectile is sent skyward with great force.  The ancient Chinese and the Romans had used this technology previously, but by the medieval age the weapons were growing in size, so that vast stones weighing over 1000 kg could be hurled at enemy castles, at a range of 300 meters.  The cycle rate was also impressive, a rock capable of being launched every 15 seconds.  These weapons were so effective that they lasted well into the 15^th Century, despite the introduction of gunpowder.