Guest blog by Alan Wilkins published on 17th April 2020

Full-scale replicas of the Roman army’s  two designs of bolt-shooting catapults, the scorpio minor and manuballista, can be viewed at the Roman Army Museum. They were kindly donated to the Vindolanda Trust by Tom Feeley, a master catapult engineer.  In the above photo Tom (on the left) is discussing the very successful live-shooting tests of his arch strut manuballista with the writer.

Tom devoted many years to a study of the equipment of the Roman army, reproducing armour, weapons etc. with the highest skill and authenticity.  These reconstructions confirm the superb quality of his metalwork in particular.

         Manuballista before display at the Roman Army Museum       


Tom Feeley’s carroballista, a larger version of the manuballista.


Greek and Roman catapults used the massive amount of energy that could be stored in rope made from animal sinews. Two separate bow arms were inserted into two vertical skeins of sinew-rope mounted in a strong frame.  Each strand of the sinew-rope was stretched around top and bottom iron washer-bars which were slotted into revolving bronze washers.  The washers and their rope skeins could be twisted with a spanner, forcing the bow arms forward.  This twisting or torsion of the rope springs was further increased when the arms were pulled back by winch to launch the bolt. This is why this type of catapult is called a torsion catapult.  It can launch bolts or stones.

Tom shooting a bolt through a water-melon with the scorpio minor catapult now on display in the Roman Army Museum

The sinew-rope torsion catapults of Greek and Roman armies were the most powerful missile launching machines in the western world from the time of Alexander the Great to the fall of the Roman Empire.

They could shoot much further than conventional weapons such as an archer’s bow, so that they could destroy an enemy army before it could come near enough to shoot back.

“…the missile is launched with such force that it reaches not less than twice the range of a shot from a bow …” 

6th century AD writer Procopius, War against the Goths i.21.17, describing the bolt launched from the metal frame arch strut catapult.


The firepower of the Roman Army

These catapults were used in battle by the Roman legions in combination with all other available weapons, even hand thrown stones, to produce a lethal hailstorm of missiles.

'Vespasian ordered his artillery, numbering a total of 160 machines …to fire at the defenders on the wall. In a coordinated barrage the catapults sent long bolts whistling through the air, the stone-throwers shot stones weighing one talent (26.2kg), fire was launched and a mass of arrows. This made it impossible for the Jews to man the wall or even the area behind it that was strafed by the missiles. For a mass of Arabian archers, spearmen and slingers was in action along with the artillery.'

An eyewitness description by Josephus, (Jewish War III, 166-8) of General Vespasian clearing enemy battlements with a barrage from his three legions at the siege of Jotapata (Palestine) in AD 69.

‘...It is expected that the indescribable volume of missiles will stop the charging Scythians from coming too close to our infantry line.’

 Hadrian’s general Arrian in AD 134, awaiting the approach of the hordes of invading Scythian Alani.

The first bolt-shooting catapult on display at the Roman Army Museum is the original Greek design, the scorpio, with a front frame made of wood reinforced with metal plates.  It first appears in about 350 BC and may have been invented by Greek engineers working for King Philip II of Macedon, the father of Alexander the Great.  It was eventually adopted by the Roman army.

The Roman Army Museum’s full-size reconstruction is the most authentic made so far because it is a millimetre accurate reconstruction of an actual frame discovered at Xanten-Wardt in north west Germany in 1999.

The Xanten-Wardt frame dates from the middle of the 1st century AD, the time of the Roman invasion of Britain.   It is no surprise that the iron heads of bolts from this size of bolt-shooter are found at the Iron Age hillforts of Maiden Castle, Hod Hill and Ham hill, three of the British strongholds captured by Vespasian at the start of the invasion in AD 43. The two bolt heads below are from Hod Hill and are on display in the British Museum.

The exact sizes of all other parts, the curved arms, stock and stand, are given in the description by Vitruvius, the engineer appointed in charge of the Roman army’s catapults by Emperor Augustus.

This design of bolt-shooter continued in use into the 2nd century AD.  Two partially completed parts from the wood frame were discovered in a Roman workshop or store, dated to about AD 140, in the 1999 excavations in front of Carlisle Castle.

One of two iron bound blocks of ash, object 27 from the Carlisle Millenium excavations. This is the exact size of the Xanten-Wardt bolt-shooter’s top and bottom frames drawn in this 1 to 1 plan.   Only two of the necessary holes have been completed.

Many of the iron catapult boltheads found at Vindolanda which are on display there and in the Roman Army Museum are of the right diameter to be launched through the hole in the front plating of the Xanten-Wardt machine.

There were several drawbacks to this design, one being that the solid frame holding the rope springs made it impossible to aim along the shaft of the bolt, as practised by archers of all periods of history, including today.  At some point before the end of the 1st century AD a completely different design of front frame was produced, made entirely of iron and eliminating the obstruction of the middle upright of the old wood frame.   This is nowadays called the arch strut catapult because of the distinctive semi-circular feature in the centre of the top strut.   This feature can be identified on catapults in scenes on the Column of Trajan in Rome which commemorates the Emperor’s campaign against the Dacians in AD 101-2.

Images of arch strut catapults from Trajan’s Column

It would be impossible to reconstruct this catapult from the evidence of these Trajan’s Column scenes alone. However, a remarkable manuscript survives, written by a Greek engineer working for the Roman army, which gives detailed measurements and coloured drawings of eight parts from a small version of this machine. It has the Greek title cheiroballistra, the equivalent of the Latin manuballista, meaning ‘hand catapult’.

The semi-circular arch in the diagram’s top strut confirms that this is the same type of bolt-shooter that appears on Trajan’s Column.   A few parts from this machine have been found in Roman forts on the Danube frontier, enabling the British scholars Eric Marsden and Alan Wilkins to use the evidence of the manuscript and the finds of parts to suggest the reconstruction of the manuballista in this Roman Army Museum display.

The Roman Military Research Society’s legionaries manning the reconstruction by Len Morgan and Alan Wilkins of the Roman army’s stone-throwing catapult.  This is the smallest size of ballista described by engineer Vitruvius, matched to stones weighing 2 Roman librae (0.65kg).

For those who are interested in reading more about this subject we recommend reading Alan Wilkins book Roman Imperial Artillery which is available in our bookshop.