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The Power of the Catapult

August 25, 2011

The fourth century B.C. saw a massive proliferation in catapults throughout the Mediterranean world. Catapults were fielded by the Greeks of Syracuse in 399 B.C. and quickly spread. The early Syracusan catapults were in fact early crossbows meant to be used by a single soldier. In order to fire larger stones and massive arrows (called bolts), double-arm torsion catapults (called ballistas or scorpions) were invented:

The catapult works by pulling back on the rope which connects the two arms. Each arm is attached to a spring made of tightly wound tensile material, usually animal sinew or horse hair. The rope is pulled back by a system of gears and pulleys, which causes the arms to bend back against the tensile material. When the trigger is pulled, the rope is released and the arms snap back into place, rapidly propelling the projectile forwards towards the target.

The vast majority of catapults in the classical world were of the above double-armed type. Single-armed torsion catapults were not invented until later and were used in more limited numbers as they were harder to aim. Counterweight catapults like the trebuchet did not appear until the late 11th century A.D., during the First Crusade.

Catapult ammunition excavated at Herodion, Israel, used during Bar Kokhba's Jewish Revolt in 135 A.D.

So how powerful was the ancient ballista? Archaeologists excavating ancient Carthage found 5,600 catapult stones used to defend the city from the Romans in 146 B.C.. The stones come in three sizes: A small size weighing about 7.7 lbs (3.5 kg), a medium size of between  8.8 and 30.8 lbs (4-14 kg) and some whopping huge rocks weighing up to 89.1 lbs (40.5 kg). Bolts fired from a ballista could be as large as 36 inches (91 cm) long, and were fitted with iron tips.[1]

How far could these catapults shoot their deadly payloads? Modern reconstructions have been sadly lacking. The BBC program Building the Impossible tried to reconstruct a Roman catapult used in the Siege of Jerusalem in 70 A.D. which reportedly fired a 57 lb (26 kg) projectile 440 yards (400 meters). Their reconstruction was only able to attain a quarter of this reported range, and the machine  broke down after only a couple of shots.

Ballista bolt heads in the Somerset County Museum, England.

The problem with most modern reconstructions is that they use modern ropes to make the torsion springs instead of sinew or horse hair. While rope is easier to come by, it also has much less tensile strength. Horsehair has greater tensile ability, and sinew even greater still. German military engineer Erwin Schramm built a series of catapults using horsehair springs in 1904. He reported that his stone throwers could launch a 1-pound (0.5 kg) lead shot over 300 meters, and a 36-inch (91.5 cm) bolt 400 yards (370 meters).[2]

Schramm's catapults are now on display in the Saalburg Museum in Hesse, Germany.

But what of catapults that used sinew? To my knowledge, no one has obtained enough animal sinew to build a reconstruction. The ancient author Agesistratus recorded that a sinew-based catapult could shoot a 27-inch (69 cm) arrow 700 yards (640 meters). E.W. Marsden believed the maximum range for most types was around 400 yards.[3]

How accurate were these catapults? Accuracy of stone-throwing catapults was limited by variations in the weight of the rocks used as ammunition. Even stones of the same size often had significant differences in weight, causing them to land in different places when fired.[4]

Arrow-firing catapults were much more accurate. Evidence for this comes from excavations at Maiden Hill in southwestern England, where Vespasian besieged a British fort in 43 A.D.. In the area around the chief’s hut inside the fort, 17 iron bolt heads were discovered. 11 of the 17 shots were direct hits on the hut. Roman siege engines could not have possibly been positioned closer than 160-190 yards (150-170 meters) away from the fort.[5]

Now for the final question, what happened when a projectile from one of these catapults hit a human being? Arrows fired from catapults could often punch through shields and armor plate. Schramm’s tests of his catapults showed that a 36-inch arrow could punch through a 1.2 inch (3 cm) thick iron-plated shield and then penetrate the person holding it.[6] During the Siege of Gaza in 332 B.C., Alexander the Great was wounded by a ballista bolt which “pierced his shield and corselet and penetrated his shoulder.”[7] In late antiquity, during the Gothic attack on Rome in 536 AD, the historian Procopius records that:

And at the Salarian Gate a Goth of goodly stature and a capable warrior, wearing a corselet and having a helmet on his head, a man who was of no mean station in the Gothic nation, refused to remain in the ranks with his comrades, but stood by a tree and kept shooting many missiles at the parapet. But this man by some chance was hit by a missile from an engine which was on a tower at his left. And passing through the corselet and the body of the man, the missile sank more than half its length into the tree, and pinning him to the spot where it entered the tree, it suspended him there a corpse. And when this was seen by the Goths they fell into great fear, and getting outside the range of missiles, they still remained in line, but no longer harassed those on the wall.[8]

A similar situation was recorded by the unknown author of The African War, an account of Julius Caesar’s campaign in North Africa in 46 B.C.:

Meanwhile, Labienus with part of his cavalry was attempting to force his way into the town of Leptis, which was garrisoned by six cohorts under the command of Saserna. The town was exceptionally well fortified and well-supplied with missile engines, so that the task of the defenders was easy and free from danger. Labienus’ cavalry persisted repeatedly in their efforts, and on one occasion a squadron had positioned itself in close formation just outside the gates when a carefully aimed dart from a scorpion struck their commanding officer and pinned him to his horse, whereupon the rest fled back to the camp in terror. This event deterred them thereafter from making assaults on the town.[9]

Yet, by far the most shocking report on the effects of the catapult comes from Josephus, describing a nighttime catapult bombardment that he witnessed during Vespasian’s siege of Jotapata during the Jewish Revolt in 67 A.D.:

The force of the spear-throwers and catapults was such that a single projectile ran through a row of men, and the momentum of the stones hurled by ‘the engine’ carried away battlements and knocked the corners off towers. There is in fact no body of men so strong that it cannot be laid low to the last rank by the impact of these huge stones. The effectiveness of ‘the engine’ can be gathered from incidents of that night: One of the men standing near Josephus on the rampart got into the line of fire and had his head knocked off by a stone, his skull being flung like a pebble from a sling some 600 yards; and when a pregnant woman was struck in the belly upon leaving her house at daybreak, the unborn child was carried away 100 yards; so tremendous was the power of that stone-thrower. Even more terrifying than the actual engines and their missiles was the rushing sound and the final crash. There was a constant thud of dead bodies as they were thrown one after another from the rampart.[10]

Ballista bolt lodged in the spine of a skeleton, Maiden Hill, England, 43 A.D..

At Maiden Hill, where Vespasian’s catapults showed their ability to accurately target the chief’s house, archaeologists have found the remains of several people who were killed by large arrows fired from Roman catapults. One skeleton has the head of an catapult bolt embedded in his spine. From the position of the arrow, it can be seen that he was hit in the stomach and the bolt penetrated through his body before lodging in his spinal column. A skull found at the site has a large gaping hole where the left eye socket used to be, with a catapult bolt again the likely cause.[11]

This is what happens when you get shot in the face with a ballista bolt. From Maiden Hill, England, 43 A.D..

As the stories from Josephus and The African War illustrate, highly accurate catapult fire could be a terrifying experience for those on the receiving end. A nighttime bombardment of the type Josephus witnessed at Jotapata, with bolts and stones whizzing out of the darkness to knock down walls and decapitate unsuspecting soldiers, must have been a horrifying experience to live through. It is easy to see why attacking forces sometimes broke and ran when faced with highly accurate catapult fire. Armor and shields could protect against arrows and swords, but against a 3-foot bolt capable of pinning a man to a tree through his armor there was no protection but to run away. Very quickly.

References:

[1] E.W. Marsden, Greek and Roman Artillery: Historical Development (London: Oxford University Press, 1969), 79-81, 86-88.

[2] Ibid., 86.

[3] Ibid., 88, 91.

[4] Ibid., 79.

[5] Alan Wilkins, Roman Artillery (Risborough, England: Shire, 2003), 20-21.

[6] Marsden, Greek and Roman Artillery, 86.

[7] Arrian, The Campaigns of Alexander, trans. by Aubrey De Selincourt (London: Penguin, 1971), 2.27.

[8] Procopius, History of the Wars, Project Gutenberg, trans. by H.B. Dewing. 1919, http://www.gutenberg.org/files/20298/20298-h/20298-h.htm (accessed July 12, 2011), 5.23.

[9] The African War in The Civil War: Together with the Alexandrian War, the African War and the Spanish War, trans. by Jane F. Gardner (London: Penguin, 1967), 29.

[10] Josephus, The Jewish War, trans. by G.A. Williamson(London: Penguin, 1959), 3.257.

[11] Marsden, Greek and Roman Artillery, 96.

Image Sources: (Header) F. Kirschen: “Die griechische Stadt”, 1918, Table 5, in: ‘Wolfgang Gaitzsch: “Hellenistische Geschützteile aus Pergamon”, Marburger Studien zur Früh- und Vorgeschichte, Vol. 16, Marburg 1994, p. 240;  http://www.armchairgeneral.com/forums/showthread.php?t=98225&page=2 (Body) http://commons.wikimedia.org/wiki/File:Ballista_%28PSF%29.png; http://holyland-pictures.com/category/judea/herodion/; http://commons.wikimedia.org/wiki/File:Ballista_bolt_heads.JPG; http://commons.wikimedia.org/wiki/File:Ancient_Mechanical_Artillery._Pic_01.jpg; http://www.stoa.org/gallery/album46; Marsden, Greek and Roman Artillery, plate 5.

Article © Christopher Jones 2011.

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