Algarradas, ballistas, catapults, onagers, trebuchets… All these projectile-launching weapons were used in antiquity and remained in force later, in the Middle Ages -some were specifically created in that period-, until the spread of gunpowder and the appearance of artillery made them obsolete. They had two characteristics in common: first, they were used in sieges; second, they were torsion machines, at least those mentioned. But there was a third, really curious: the use of human hair in their manufacture.

The torsion system was nothing more than an advance on the tension system, simpler and therefore older. The difference was that the latter was limited to tensing a launching arm by dragging while the other did so by twisting the transmission belt parallel to its axis. The origin of siege engines is difficult to establish. Chinese sources refer to the period of the Warring States, between the 5th and 3rd centuries BC, referring to systems that worked on the lever principle.

In that sense, the chronology would be similar to the Western one, which is located in Greece of the 4th century BC, approximately, with the gastraphetes as the primordial representative: no specimen has been preserved but according to the description left by Heron of Alexandria in his work Belopoeica, it was a kind of large crossbow (with a bow about 4 meters long) that would have been devised by the mathematician and inventor Ctesibius and could throw 18 kilo stones more than 200 meters away.

Chinese catapult mounted on a cart/Image: Liang Jieming on Wikimedia Commons

The first torsion artifact would have appeared at the end of that third century, as an inventory of the Chalcotheca of Athens (one of the buildings of the Acropolis, which served as an armory) recorded the presence of torsion machines and auxiliary elements such as bolts, projectiles or hair. Why hair? Because it was one of the components of the belt, by providing resistance to the elasticity of the animal tendons that were also used to make said belt. We’ll see that later.

It is said that Philip of Macedon, the father of Alexander the Great, used torsion machines in his campaigns, although it is more speculation than certainty. In any case, around that time their use spread throughout the Mediterranean, perfecting the manufacturing technique. The Romans did not have such weapons until well into the Republic; Livy recounts that Scipio Africanus seized 120 large catapults in Cartago Nova (today’s Cartagena, Spain), 281 small ones, 75 ballistas and numerous scorpions, making clear their profusion in the Punic Wars.

In fact, the Romans had also reached a high level in siege machinery based on Hellenic models, redesigning them to be disassembled and facilitate their transport, a factor that led to the birth of the carroballista (a ballista installed on a cart, as can be seen on Trajan’s Column) and the onager (a small single-arm catapult equipped with wheels): each legion incorporated ten of the former and 55 of the latter (one per cohort), leading to the creation of specialists in their handling called ballistarii.

Reconstruction of a carrobalista/Image: public domain on Wikimedia Commons

Vegetius, Ammianus Marcellinus, Procopius, Diodorus Siculus, Flavius Josephus and the anonymous work De rebus bellicis, among many others, bear witness to more torsion engines that were added already in imperial times, without the arrival of the Middle Ages supposed a rupture. Arab, Frankish and Saxon sources mention ballistas but it is difficult to establish with certainty whether it was exactly that or other weapons, given the tendency there was to use the terminology loosely; it is assumed that torsion artifacts coexisted with tension ones.

Not even the treaty that Mardi ibn Ali al-Tarsusi wrote for Saladin in the 12th century and which is considered the most complete on the subject, references more than trebuchets (the first news about them, by the way). Other medieval references also speak of mangonels (catapults capable of launching projectiles 400 meters although without the precision that trebuchets would later achieve), but it was common to mention these machines in a generic way, which prevents knowing exactly what models were involved.

Reconstruction of a trebuchet/Image: ChrisO on Wikimedia Commons

Some 19th century scholars believed that there was a technological setback in that field in the Middle Ages due to the difficulty in finding tendons and metal parts (for example, the washers that protected the skein from fraying due to friction with the wood), so tension and counterweight engines would have been returned to; the absence of archaeological record would support that thesis.

However, later in that century dissenting voices arose denying it considering that the lack of material evidence is not enough, given the documentary ones, which also had illustrations showing their appearance. The debate is still open.

Indeed, as they were wooden artifacts, perishable material, hardly any specimens of torsion machines have been preserved beyond some loose parts, precisely those that were metal. However, there are some and the first major case was found in 1912 in Ampurias, with others appearing in the second half of the 20th century in Gornea (Turkey), Orşova (Romania), Cremona (Italy), Volubilis (Morocco), Hatra (Iraq), etc. What there are by the thousands are projectiles, since they were usually stone, with various weights between 4.5 and 39 kilos.

It is clear that the structure of the engines was made of wood, reinforced at key points by metal clamps. But there was also the skein, which was the differentiating element of the torsion system with respect to the tension system. It consisted of a series of strands wound in a spiral around the frames, remaining tense. When the weapon had to be loaded, this skein was rotated by means of handles on both sides, tensing it even more and lowering the launching arm, whose base is held between said strands. When firing, a force superior to that of the tension system was achieved, which was based on a simpler principle: that of the bow.

Antique illustration depicting a carroballista (1552 edition of De rebus bellicis)/Image: public domain on Wikimedia Commons

We said before that this skein was sometimes made with animal tendons, especially horse, and sometimes with human hair, mainly female for the obvious reason that it was longer. There depended on tastes, because if the Greek Heron of Alexandria and the Roman Vegetius coincided in preferring tendon, Vitruvius opted for hair, often horsehair but sometimes human if circumstances were desperate.

It was considered that the best tendons were those from the legs of horses or deer and those from the necks of oxen. According to some researchers, it was a very elastic material, something that was preserved by smearing olive oil or fat; but at the same time it presented great resistance, much greater than that of a wooden beam, for example, and without being affected by the high Mediterranean temperatures. The average life of a tendon was estimated at between 8 and 10 years.

The skeins of human hair are known to be related to Rome, where in early times women donated their hair in extreme situations (later Carthaginians did too), something that symbolized their sacrifice because having short hair was considered a sign of neglect and indecency (it had to be worn long but gathered), as described by some classical sources such as Virgil. Also, as in the previous case, they were smeared to protect them and could be combined with tendons to give cohesion to the whole.

This article was first published on our Spanish Edition on January 16, 2019. Puedes leer la versión en español en Cuando las mujeres romanas donaban su pelo para las catapultas


De re militari (Vegecio)/Los diez libros de arquitectura (Marco Vitruvio)/The wars of Justinian (Prokopios)/Artillería y poliorcética en el mundo grecorromano (Rubén Sáez Abad)/Greek and Roman Artillery 399 BC–AD 363 (Duncan B. Campbell)(Greek and Roman artillery. Historical development (Eric William Marsden)/Proyectiles de catapulta romana procedentes de la fortificación de La Espina del Gállego (Cantabria). Estudio y tratamiento de conservación (Carmelo Fernández Ibáñez)/Wikipedia

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