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Under Siege - a history of siege weapons

Updated: Aug 22, 2019

The concept of an arms race is an old one. One tribe tries to protect itself from other tribes by building defences and other tribes develop weapons and techniques to over come the defences. Better defences are then built, then better offensives and so the cycle continues.

Here is a list of the major weapons used throughout history in siege warfare. At the bottom are some top tips for building your perfect defences

Siege Weapons

Siege tower

An army marches to the walls with its assembled siege tower.

Use: Surmounting battlements

Earliest evidence: 11th Century BC by Babylonians and Assyrians

Key traits: Tall armoured vehicle with ladders inside

Also known as: Breach Tower or Belfry (Middle Ages)

The siege tower was one of the first answers to defensive walls, the first probably being simply the use of ladders (scaling walls with ladders is called "escalade"), and was a large wooden tower on wheels. Inside there were several levels with ladders for people to climb. The siege tower was then pushed towards the defensive wall and a plank, or draw bridge, would be dropped. The soldiers who were inside would then rush out on to the ramparts. Defenders had an advantage as siege towers were big and slow-moving targets and would hurl rocks, arrows and even vats of burning liquids at the oncoming assailants. Archers inside the towers would return arrows in an attempt to make for an easier breach.

One famous siege tower was used in the siege of Rhodes in 305 BC and was called Helepolis (meaning “taker of cities). However, the defendants flooded the ground in front of the walls and the tower became stuck in the mud.

In AD 626 when the Avars laid siege to Constantinople they employed the used of “sows”, which, under cover, filled in sections of the moat to allow the advancement of siege towers.

*honourable mention* In AD 73 the Roman Legion X Fretensis under the leadership of Lucius Flavius Silva laid siege to the fortress at Masada. Using local soil, they constructed a ramp over the course of 2-3 months finally breaching the walls only to find that the near 1,000 defendants had committed mass suicide.

Battering ram

An example of a framed battering ram with a roof for protection from falling rocks and hot oil.

Use: Breaking through defences

Earliest evidence: 9th Century BC by the Assyrians

Key traits: large log or weight swung to provide shock on impact

The earliest reference to battering rams is from a carving of an Assyrian assault on another town, however the earliest confirmed use is by the Romans against the Aurunci in 502 BC.

In its simplest form a battering ram is simply a log held by a team of men and systematically thrust against a door, gate or other defences to weaken and force it open. Modern day police use a small-scale equivalent in house raids today. Other additions could include a metal weight on the end to add force, shelter from the defenders above (this could be handheld or mounted) and a frame for the ram to be hung onto allowing for a heavier ram to be deployed.


Ballistae and catapultae came in various shapes and sizes over the ages.

Use: throwing projectiles (rocks and bolts)

Earliest evidence: circa 400 BC by Dionysius of Syracuse (Greek)

Key traits: torsion powered weapon

Related to: Catapulta and Scorpio

The term ballista (or ballistae for plural) comes from the Greek “ballo” meaning to throw.

The Greeks invented the first crossbow called a belly bow (or gastraphetes if you want the proper name), which used a person’s body weight to help cock the weapon. The gastraphetes was powered by storing energy by bending the arms of the bow (just like any other bow). However, in circa 400 BC the Greeks created a wooden frame through which they looped sinew (string made from the tendons of an animal) and threaded the arms into the bundle. Twisting the arms stores energy in the sinews, which is called Torsion power. The advantage of torsion power is that it can be scaled up to almost any size and had better range than the belly bow.

A similar torsion powered weapon to the ballista was the catapulta (where we get the term catapult from). The name “catapulta” again comes from Greek meaning “down-thrower”. Exactly what the difference was between the catapulta and the ballista is unclear, and the two terms may have been used as synonyms by contemporaries. Today, however, the term catapulta tends to be used to refer to the bolt throwing variety and ballista to the stone throwing variety, though in the past it appears that both catapultae and ballistae threw both bolts and rocks.

You can experience torsion power by stretching an elastic band between your thumb and finger, putting a ruler in between and twisting. You will feel the elastic band pulling on the ruler back the way it has come.

*Honourable mention* In the 3rd Century BC the Greeks invented an “automatic” version of the ballista called a Polybolos (meaning “many-thrower”). A box full of bolts was fitted to the body and a single bolt was dropped periodically in front of the tensioned string at the appropriate moment


An onager, loaded and being put under tension.

Use: throwing projectiles (mostly rocks)

Earliest evidence: first mentioned in AD 353 by Ammianus Marcellinus (Roman)

Key traits: torsion powered weapon

Also known as: Scorpio

The onager was similar to the ballista, but instead of having two arms protruding horizontally like a bow the onager had one arm protruding vertically like a giant tail with a sling at the end. The term “Onager” means “wild ass” presumably because of the kick that it gives when released.

The onager was also referred to as a scorpio (scorpion) by contemporaries due it’s tail that would give a sting to those that it was pointing at. Confusingly the term scorpio historically has been used to refer to both the onager and a smaller version of the ballista.

Used mostly against forts and settlements the onager was used to throw rocks, which could also be doused in flammable liquid and set alight to add to the destruction that the Romans were trying to afflict.


A mangonel or traction trebuchet, with the sling for the projectile to the right and the many ropes for the crew to pull down on to the left.

Use: throwing projectiles (mostly rocks)

Earliest evidence: 4th Century BC in China

Key traits: Man powered weapon

Also known as: Perrier & Traction Trebuchet

The traction trebuchet, or more commonly referred to as the mangonel, was initially developed in china in the 4th Century BC. It first appeared in Europe in the Mediterranean in the 6th Century AD. It was more reliable than the torsion powered onager as the sinews could become slack if wettened or even snap, sometimes with catastrophic consequences. Not only did the mangonel omit these issues but it easily matched the onager in range and was quicker to reload.

The mangonel consisted of a single, vertically swinging, arm like the onager but it was mounted higher up. It had several ropes attached to the short end and a sling attached to the long end into which the projectile was placed. A team of men each held a rope and on the given signal they all pulled down in unison flinging the long side of the arm up and releasing the projectile forwards.

Onagers were sometimes referred to as mangonels by contemporaries as the term was used to refer to an engine that threw stones (just like the term catapult today)


A trebuchet, cocked and ready to unleash a huge rock towards that castle!

Use: throwing projectiles (mostly rocks)

Earliest evidence: AD 1187 by Mardi ibn Ali al-Tarsusi on the conquests of Saladin

Key traits: Gravity powered weapon

Also known as: Counterweight Trebuchet

The trebuchet was an evolution of the Chinese invented mangonel though, instead of using soldiers to pull on ropes for power, the trebuchet has a huge bucket full of rocks attached to the short end to store energy.

Using a winch, a rope is attached to the arm (held upright by the weight of the bucket pulling down) and the arm is drawn downwards. When at the bottom a pin is fitted to hold the arm down and the winch mechanism is disconnected. Ammunition is loaded into the sling and the pin is pulled out allowing the bucket to fall throwing the arm, sling and projectile in an upwards arc. When the arm reaches the top, the projectile is thrown forwards towards the target.

The size of the trebuchet varied considerably with the largest in record being the medieval Warwolf, used by the English in the the Scottish Wars of Independence, which modern experts estimate stood between 3-400 feet tall and was easily capable of throwing projectiles 200 yards (outside of archery range) at 120 miles per hour. The modern recreation held at Warwick Castle has a range of 300m, and it's power and devastating capabilities were demonstrated when operators accidentally struck and damaged a Victorian boat house on the River Avon.

The trebuchet is regarded to be the most efficient siege engine pre gunpowder.


Cannons (and gunpowder) are where we get the term "to fire" a projectile!

Use: launching cannon balls (carved round rocks)

Earliest evidence: Depicted in China in the 12th Century

Key traits: Uses gunpowder to propel projectile

Although it appears that cannons are depicted in Chinese art in the 12th Century, archaeological evidence certainly confirms their use in the 13th Century. By 1326 depictions of cannons could be found in Europe and their use soon followed.

Cannons became a complete game changer in warfare and would eventually come to end the era of knights, castles and the Middle Ages towards the end of the 15th Century.

There have been some pretty big cannons over the centuries but some of particular note are:

  • Mons Meg - The largest cannon ever put to sea (now in Edinburgh Castle)

  • Humpty Dumpty – A cannon used by the Royalists in the English Civil War (it fell from battlements and broke)

  • Basilica – One of the Ottoman Empire’s super cannons that was used to destroy the walls of Constantinople and caused the fall of Byzantium in AD 1453 to Sultan Mehmet II

Siege Tactics

Accompanying siege weapons, clever tactics have allowed assailants to overcome sometimes impregnable defences.


The tunnel is dug and the fire is lit, better get out of there quick as there is only one way for air to come in and smoke to get out. Plus, you don't want to be underneath that wall when it comes down!

Just like the song “Going on a Bear Hunt” if you can’t go through it or over it, why not try under it! The purpose of undermining is not so the whole army can pass through but to weaken the walls. As the mine is being dug timber supports are put into hold the weight above. Once a sufficient size the mine is packed with combustible material evacuated and set alight. Once the timbers have burnt through the support for the wall has gone and the wall will crumble.

Corners were the best part to mine as straight walls could hold themselves up. This gave rise to building round towers on the corners of walls and keeps as they were much harder to break down with mining.

Build another wall!

When Julius Caesar faced a much larger force in Gaul (now France), led by the chieftain Vercingetorix in the Gallic uprising, he besieged them in their fortress in Alesia. Julius Caesar built a wall around their fortress so that they could not escape. Eventually the Gauls started to run out of food and disease started to spread, there were even rumours of cannibalism. However, Caesar heard that a second Gallic army was approaching so he built another wall around the first wall. Long story short the Romans won, and Vercingetorix surrendered by throwing down his weapons at Caesar’s feet.

Field scorching

In the Peloponnesian wars Sparta struggled to capture Athens so they invaded every year, burnt all the crops they could find and returned home. The plan was to weaken Athens in the long run so that they could be more easily subdued. Athens responded by constructing a 7km long walled corridor to its nearest port Piraeus however many people had taken refuge from the invading Spartans and the depleted farms and an outbreak of plague killed approximately 30,000 people. Sparta finally won their victory by developing its own navy and defeating Athens at sea.

Encouraging disease (biological warfare)

Catapults not only could be used to hurl rocks at walls. They could also be used to throw dead animals and disease-ridden corpses into defences.

In the siege of Rouen, AD 1418-19 the English threw dead animals into the wells to poison the water supply to the town. Also, in AD 1347 at the siege of Caffa, the plague was ripping through the attacking Mongols killing hundreds a day. The Mongols threw the diseased corpses into the city of Caffa and the defenders couldn’t dispose of the bodies fast enough. Quickly the plague started to spread across the defenders as well.


Some defences were so good that they only fell when betrayed from the inside. In 1645 Corfe Castle was now under siege for the second time by the Parliamentarians. It only fell because some of the garrison were secret Parliamentarian supporters who aided in the attacking force breaching the walls.

Best defences

It is said that you can either learn from the mistakes of others or you are doomed to make them yourself! Here are our 13 top tips for surviving an historic siege:

  1. Make sure that you have an abundant source of clean drinking water. But be careful, wells are easily poisoned. To be safe keep a guard on duty. For added security you can turn the water into beer as the alcohol kills germs that can make your people sick.

  2. Also make sure that you have a supply of water to put out any fires that break out.

  3. Have a good stockpile of firewood to keep warm, cook food and to burn bodies if needed to stop the spread of disease.

  4. Have a large supply of food that won’t rot or decay.

  5. Make sure that you have enough space to accommodate extra people fleeing from the attackers but not have too big a fortification so as to make it difficult to defend.

  6. Have well trained and loyal soldiers

  7. Maintain strong discipline. One mistake could cost many their lives.

  8. Site your defences in open terrain for good visibility. You can then see enemies coming with plenty of warning making it easier to defend.

  9. It’s always easier to defend the high ground. Plus being higher than your opponent gives you longer range for your missiles.

  10. Moats are great at defending against siege towers and undermining (if anyone did try mining, they would get very wet)!

  11. Build your defences with strong thick walls and avoid corners (have round towers instead).

  12. Having your defence on the coast means you can receive supplies and reinforcements during the siege. It also restricts the area that invaders can attack.

  13. Build in defences such as short-range siege engines and murder holes (they are holes for… well you can figure it out) so that you can stop attackers trying to scale the walls.

Happy defending (or attacking)!

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