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A Guide to Roman Artillery - A Speedy Read

Updated: Nov 22, 2023

The Roman Army was undoubtedly the most dangerous in all of ancient history. One reason for the Roman Army’s sheer awesomeness was down to the Legionnaire’s extensive training. Rather than being enthusiastic farmers armed only with a pitchfork and a case of severe drunkenness – as it was for the 'soldiers' of many armies - Legionnaires were instead professional soldiers, each warrior armed with the most technologically advanced weapons and armour to be found, anywhere.

Not only that, but the Legions were really well organised, they could change to different battle formations as quickly as a pig coated in grease can zoom down a waterslide. Hundreds of soldiers could switch from the Wedge, to the Testudo and the Triple Line (more on Roman Battle Formations in an upcoming blog!) as the battle demanded.

So, as you can imagine, when the Roman Legions marched to war, their foes were definitely quaking with fear. Adding to the Legion’s fearsome reputation was the fact that they brought artillery into battle. These enormous engines of destruction could launch burly boulders, razor-sharp bolts, and piercing arrows over vast distances with lethal accuracy. Let’s take a closer look at these terrifying devices, shall we?

The Onager

A fantastically accurate - and very cute! - replica of a Roman Onager by Pathfinders: Design and Technology

An Onager was a big wooden catapult that could launch chunky stones through the air with ease. So what did Onager look like? Well, they kind of looked like a big square wooden frame with a giant spoon - called an arm - attached to the top. At the end of the arm would be a bucket or sling, in which a rock that wanted lobbing would be placed.

A diagram of an Onager, courtesy of Rpanjwani3.

It then took all the strength of eight men to force the arm into position. It was so difficult as the soldiers had to overpower a number of twisted ropes and springs to lock the arm into place. All those ropes and springs ensured there was plenty of tension and that the Romans got a good workout in too. This tension, once released, created a force that could throw the stone 130 meters, crushing to jelly anything in its path.

Onagers were used to lay siege on enemy fortresses. They would launch rocks to damage the walls and to distract the inhabitants whilst a Roman battering ram smashed the fortresses’ doors wide open.

Because Onagers were so big, heavy, and cumbersome, engineers accompanying the Legion would build them once the Romans had arrived at their destination! Clever, huh?


We love this model version of a Roman Ballista by Warlord Games.

A Ballista was like a massive crossbow. And I really mean massive. Built on a wooden frame, the Ballista had two arms at its front that measured around a meter and a half in length. Strapped and wrapped around these arms was a twisted cord – made from horsehair, which means there must have been a lot of poor shaved horses wandering around the Roman Empire - that would be wound back into position with a winch. Once the cord was in place, a stone, bolt, or arrow would be loaded onto the Ballista. With a twang – no, scratch that, with a TWANG!!! – the torque built up by the cord was released and the stone, bolt, or arrow was hurled 400 meters through the air.

Here's a replica of a smaller Ballista, called a Scorpio, being fired at a Roman Re-enactment Event. Image courtesy of Matthias Kabel.

It took a team of 10 Romans to load and fire a Ballista, but with enough skill, they could launch three to four nasty objects hurtling through the air every single minute! Whoever got hit by one of those would be having a really bad day!

Ballistae came in all sorts of different shapes and sizes.


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