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Roman siege engines

Roman  siege engines   were, for the most part, adapted

from  Hellenistic  siege technology. Relatively small ef-

forts were made to develop the technology; however, the

Romans brought an unrelentingly aggressive style to siege

warfare[1] that brought them repeated success. Up to the

1st century BC the Romans utilized siege weapons only

as required and relied for the most part on ladders, tow-

ers and rams to assault a fortified town. Ballistae were

also employed, but held no permanent place within a le-

gion’s roster, until later in the Republic, and were used

sparingly.  Julius Caesar took great interest in the integra-tion of advanced siege engines, organizing their use for

optimal battlefield efficiency.[2]

1 Army engineering corps

Roman springald .

Main article: Roman military engineering

To facilitate this organization and the army’s self-

sufficiency, an engineering corps was developed. An of-

ficer of engineers, or praefectus fabrum, is referenced in

armies of the Late Republic, but this post is not verifi-

able in all accounts and may have simply been a military

advisor on the personal staff of a commanding officer.[2]

There were legion architects (whose rank is yet unknown)

who were responsible for the construction of war ma-

chines who would also assure that all artillery construc-

tions in the field were level. Ensuring that construc-

tions were level was the job of the   libratores , who would

also launch missiles and other projectiles (on occasion)

during battle (Le Bohec 1994: 52). The engineering

corps was in charge of massive production, frequentlyprefabricating artillery and siege equipment to facilitate

its transportation.[1]

2 Artillery

Roman siege engines 

Roman artillery was very efficient at that time, and dur-

ing a siege the Romans would attack the weakest area of

their enemy’s defenses and attempt to breach the walls at

that point. To support this effort, artillery fire would com-

mence, with three main objectives:[3] to cause damage to

defenses, casualties among the opposing army, and loss ofenemy morale. It would also provide cover fire for troops

building siege ramps or those in siege towers. There

were machines called   tormenta   , which would launch

(sometimes incendiary) projectiles such as javelins, ar-

rows, rocks, or beams. These devices were on wheeled

platforms to follow the line’s advance. All were “predi-

cated on a principle of physics: a lever was inserted into

a skein of twisted horsehair to increase torsion, and when

the arm was released, a considerable amount of energy

was thus freed”.[3] It was later stated that sinew, instead

of twisted hair, provideda better “spring.” Theseweapons

were high-maintenance devices and vulnerable to having

their leather, sinew, or hemp skeins affected by wet oreven damp, which would cause them to slacken and lose

tension, rendering the engine useless.[4]

It is somewhat difficult to clearly define and describe Ro-

man artillery, as names are easily confused and historians

still do not agree on all definitions. Perhaps best known

are the ballista, the onager , and the scorpio.

2.1 Ballista

Main article: Ballista

After the absorption of the Ancient Greek City statesinto the   Roman Republic   in 146 BC, some advanced

Greek technology began to spread across many areas of

1

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2   2 ARTILLERY 

Roman arrow machine.

One talent ballista (26 kg weight projectile). The heaviest versions 

could shoot up to three talents (78 kg), possibly much more.[5]

A ballista.

Roman influence. This included the hugely advantageous

military advances the Greeks had made (most notably by

Dionysus of Syracuse), as well as all the scientific, math-

ematical, political and artistic developments.

The Romans 'inherited' the torsion powered Ballistae

which had by now spread to several cities around the

Mediterranean, all of which became Roman spoils of war

in time, including one from  Pergamum, which was de-picted among a pile of 'trophy' weapons in relief on a

balustrade.

The torsion ballista, developed by Alexander, was a far

more complicated weapon than its predecessor, and the

Romans developed it even further.

Vitruvius, in his  De Architectura  Book X, describes the

construction and tuning of Ballistae.

Every century (group of 60-100 men) in the Roman army

had a ballista  by the 1st century AD.[6] It was the com-

mand of the chief of the ballista, under whom were the

artillery experts, or doctores ballistarum  and finally, the

artillerymen, or ballistarii .[7] Ballistae were heavy missile

weapons, hurling large rocks great distances to damage

rampart walls. They resembled large crossbows, rather

than catapults. They were powered by two horizontal like

arms, which were inserted into two vertical and tightly

wound “skein” springs contained in a rectangular frame

structure making up the head or principal part of the

weapon. The arms were drawn rearward with a winch

lever to further twist the skeins and thus gain the tor-

sion power to cast a projectile.[4] It has been said that the

whirring sound of a ballista-fired stone struck fear and

dread into the hearts of those inside the walls of besieged

cities. The stones chosen to be used in the ballista had tobe a particular sort. According to Vegetius river stones

were best, since they are round, smooth, and dense. Bal-

lista stones found at the site of Masada were chiseled to

make them as round as possible.[8]

2.1.1 Early Roman ballista

Roman 'catapult-nest' on Trajan’s Column

The early Roman ballistae were made of wood, and held

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2.2 The Onager    3

Ballista, military equipment of ancient Rome.

together with iron plates around the frames and iron nails

in the stand. The main stand had a slider on the top, into

which were loaded the bolts or stone 'shot'. Attached to

this, at the back, was a pair of winches and a claw, used

to ratchet the bowstring back to the armed firing position.

A slider passed through the field frames of the weapon,

in which were located the torsion springs (rope made of

animal sinew), which were twisted around the bow arms,

which in turn were attached to the bowstring.

Drawing the bowstring back with the winches twisted the

already taut springs, storing the energy to fire the projec-

tiles.

Theballista was a highly accurate weapon (there are many

accounts right from its early history of single soldiers be-

ing picked off by the operators), but some design aspects

meant it could compromise its accuracy for range. The

lightweight bolts could not gain the high momentum of

the stones over the same distance as those thrown by the

later onagers, trebuchets, or mangonels; these could be as

heavy as 90-135 kg (200-300 pounds).

The Romans continued the development of the Ballista,

and it became a highly prized and valued weapon in the

army of the Roman Empire.

It was used, just before the start of the Empire, by

Julius Caesar  during his conquest of  Gaul   and on both

of his expeditions to Britain. Both attempted invasions

of Britain and the siege of Alesia are recorded in his own

Commentarii  (journal),  The Gallic Wars   (De Bello Gal-

lico). It was also used in the Roman siege of Masada.

2.1.2 First invasion of Britain

The first invasion of Britain took place in 55 BC, after

a rapid and successful initial conquest of Gaul, in partas an exploratory expedition, and more practically to try

and put an end to the re-enforcements sent by the native

Britons to fight the Romans in Gaul.

A total of eighty transports, carrying two legions at-

tempted to land on the British shore, only to be driven

back by the many British warriors assembled along the

shoreline. The ships had to unload their troops on the

beach, as it was the only one suitable for many kilometers,yet the massed ranks of British charioteers and javeliners

were making it impossible.

Seeing this, Caesar ordered the warships –

which were swifter and easier to handle than

the transports, and likely to impress the na-

tives more by their unfamiliar appearance – to

be removed a short distance from the others,

and then be rowed hard and run ashore on the

enemy’s right flank, from which position the

slings, bows and artillery could be used by men

on deck to drive them back. This manoeuvre

was highly successful.

Scared by the strange shape of the warships,

the motion of the oars, and the unfamiliar ma-

chines, the natives halted and then retreated a

little. (Caesar, The Conquest of Gaul , p. 99)

2.1.3 Siege of Alesia

In Gaul, the stronghold of  Alesia   was  under a Roman

siege in 52 BC, and surrounded by Roman fortifications.

As was standard siege technique at the time, ballistae

were placed up in the towers with other soldiers armedwith either bows or slings.

2.2 The Onager

Main article: Onager (siege weapon)

The   onager   was a post-classical Roman siege engine,

Sketch of an Onager, from  Antique technology by Diels 

which derived its name from the kicking action of the

machine, similar to that of an  onager   (wild ass). It isa type of  catapult  that uses  torsional  pressure, generally

from twisted rope, to store energy for the shot.

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4   3 BREAKING THE WALLS 

The onager consisted of a frame placed on the ground

to whose front end a vertical frame of solid timber was

rigidly fixed; through the vertical frame ran an axle, which

had a single stout spoke. On the extremity of the spoke

was a sling used to launch a projectile.

In action the spoke was forced down, against the tensionof twisted ropes or other springs, by a windlass, and then

suddenly released. The spoke thus kicked the crosspiece

of the vertical frame, and the projectile at its extreme end

was shot forward.

The onagers of the Roman Empire were mainly used

for besieging forts or settlements. They would often be

loaded with large stones or rocks that could be covered

with a flammable substance and set alight.

In the Middle Ages   (recorded from around 1200 C.E.)

a less powerful version of the onager was used that em-

ployed a fixed bowl rather than a sling, so that many small

projectiles could be thrown, as opposed to a single largeone. This engine was sometimes called the mangonel , al-

though the same name may have been used for a variety

of siege engines.

2.3 Scorpios

Main article: Scorpio (dart-thrower)

The scorpio was a crossbow-like device that fired smaller

Modern reconstruction of a Scorpio

arrows with deadly accuracy[2] used both in the field

and in sieges. They were so-named for their deadly,

armor-piercing sting and could be operated by just one

or two men. Scorpios were meant to kill and injure en-

emy troops, rather than break down enemy fortifications.

Thanks to their smaller size, they could be mounted on or

in siege towers. During the Siege of Amida, a scorpion-

fired arrow killed theson of Grumbate, king of the Chion-

itae, when he was approaching the city to surrender.[9]

There has been some research done into the exis-

tence of the self-loading, serial-fire  scorpio or polybolos.Legionaries either side would continuously keep turning

cranks which turned a chain, which operated the various

mechanisms to load and fire the catapult. All that was

needed was for another soldier to keep feeding in more

arrows.[10]

3 Breaking the walls

3.1 Battering rams

Main article: Battering ram

Roman battering rams, or   aries , were an effective

Roman battering ram.

A battering ram (aries) with a shed (testudo). After a relief on

Septimius Severus ' triumphal arc in Rome.

weapon for breaking down an enemy’s walls, as well as

their morale. Under   Roman law, any defenders who

failed to surrender before the first ram touched their wall

were denied any rights.[11] The moment they heard the

ram hit the wall, those inside the city knew that the siege

proper had begun and there was no turning back.[12]

Josephus  describes the battering ram used at   Jotapata

thus:[13]

It is an immense beam, similar to a ship’s

mast, with one end covered with iron shaped

into a ram’s head; hence its name. It is sus-

pended from another beam like a balance arm

by cables around its middle, and this in turn

is supported at both ends by posts fixed in the

ground. It is drawn back by a huge number of

men who then push it forward in unison with all

their might so that it hits the wall with its ironhead. There is no tower strong enough nor any

wall thick enough to withstand repeated blows

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3.3 Mines    5

The remains of the Roman siege-ramp at  Masada

of this kind, and many cannot resist the first

shock.

Vitruvius  in  De Architectura  Book X describes the con-

struction and use of battering rams.

For protection, a battering ram was suspended in a mo-

bile shelter called a tortoise, or  testudo. According to

Vegetius, it was given this name because the ram would

swing out of the shelter much like a tortoise’s head comes

out of its shell. Such shelters would provide the men

within protection against missiles and incendiary devices.

They were constructed from a framework of strong tim-

bers with planks and wicker hurdles on the sides. The en-

tire shelter would then be covered with a fireproof mate-rial such as uncured hides.[14] According to Apollodorus

of Damascus, the shelter should be fixed to the ground

while the ram was being used to both prevent skidding

and strain on the axles from the weight of the moving

apparatus. This would also increase the strength of the

impact on the walls.[15]

3.2 Siege towers

Main article: Siege towers

According to   Josephus, the Roman siege towers at

Jotapata were 50 feet high and iron-plated to protect them

from fire; those at  Masada were reported to be 75 feet

high. It was possible to have many different devices on

siege towers, such as artillery,   draw bridges  and rams.

Those at the top of the tower were to keep defenders off

the walls while those below them attempted to breach the

wall using ramps. In the battle of Jerusalem in 70 AD the

Romans began assault on the third defensive wall within

Jerusalem, the tower stood 75ft tall and was compromised

when the Jewish resistance tunneled underneath the tower

leading it to collapse.   [16] Following a basic design, details

of tower construction varied from siege to siege and thereis no known treatise which specifies at which level siege

equipment should be placed.   Vegetius noted that, “be-

Siege Machine.

siegers sometimes built a tower with another turret inside

it that could suddenly be raised by ropes and pulleys to

over-top the wall”.[17]

3.3 Mines

Mines  could be dug under city walls as a means of en-

tering a city secretly and capturing it but were more fre-quently constructed to weaken city walls. Once dug,

sappers would underpin the walls with wood and cause

the walls to collapse by firing the supports with resin, sul-

fur and other incendiary materials.[18]

4 See also

•  Roman engineering

•   Vitruvius

5 Notes

[1] Goldsworthy 2000: 144

[2] Keppie 1984: 99

[3] Le Bohec 1994: 138

[4]  Catapulta at LegionXXIV

[5] Werner Soedel, Vernard Foley: “Ancient Catapults”,

Scientific American, Vol. 240, No. 3 (March 1979),

p.120-128 (121ff.)

[6] Le Bohec 1994: p. 138

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6   6 REFERENCES 

[7] Le Bohec 1994: p. 49

[8] Garrison 1997.

[9] Goldsworthy 2000: 191

[10]   Siege weapons at roman-empire.net

[11] Goldsworthy 2000: p. 145

[12] Gilliver 1999: p. 140

[13] Le Bohec 1994: p. 139

[14] Gilliver 1999: pp. 134-135

[15] Gilliver 1999: p. 138

[16] Gilliver 1999: pp. 136-137.

[17] Gilliver 1999: 138

[18] Gilliver 1999: 140

6 References

•   James V. Garrison (1997). “Casting stones: ballista,

stones as weapons, and death by stoning”.  Brigham

Young University Studies  36  (3): 351–352.

•   Gilliver, C.M. (1999).   The Roman Art of War .

Charleston, SC: Tempus. ISBN 0-7524-1939-0.

•   Goldsworthy, Adrian (2000).   Roman Warfare.

London: Cassell. ISBN 0-304-35265-9.

•  Keppie, Lawrence (1984).  The Making of the Ro-

man Army from Empire to Republic . Totowa, NJ:

Barnes & Noble Books.  ISBN 0-389-20447-1.

•   Le Bohec, Yann (1994). The Imperial Roman Army.

London: B.T. Batsford Ltd. ISBN 0-7134-7166-2.

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7

7 Text and image sources, contributors, and licenses

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Schulz, No Guru, Discospinster, Rich Farmbrough, Mairi, Melaen, Nicknack009, Allen3, Rjwilmsi, RussBot, Gaius Cornelius, Baranxtu,

Katieh5584, Sardanaphalus, Attilios, Gilliam, Hmains, Cplakidas, Glloq, John, Peterlewis, Neddyseagoon, Cgeislerwyo, Jaeger5432,

Michaelas10, Gogo Dodo, Epbr123, Marek69, Folantin, Gioto, VoABot II, Fabrictramp, Edward321, Gun Powder Ma, SquidSK, R'n'B,

Verdatum, Ssolbergj, Nev1, PocklingtonDan, 07UNCBean, Squids and Chips, Jalo, SieBot, Caltas, Yintan, Granite07, Sfan00 IMG, Clue-

Bot, Mild Bill Hiccup, Excirial, Alexbot, Saturnian, Ludwigs2, Junglerot56, Trex2001, Bilsonius, Addbot, DOI bot, West.andrew.g, Light-

bot, Picture Master, Yobot, Fraggle81, Materialscientist, Omnipaedista, Citation bot 1, Imperial fodder, Zeta1127,89thLegion, ClueBot

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