https://www.labrujulaverde.com/en/2025/05/evidence-of-the-use-of-a-polybolos-the-mythical-greek-repeating-weapon-at-pompeii-in-89-bce-discovered/
Evidence of the Use of a Polybolos, the Mythical Greek Repeating Weapon, at Pompeii in 89 BCE Discovered
A team of Italian researchers has discovered markings on the walls of Pompeii that could be the first known evidence of the use of an ancient and sophisticated weapon of war: the polybolos, a type of automatic crossbow capable of launching multiple arrows without needing to be reloaded, similar to modern machine guns.
Its invention is attributed to Dionysius of Alexandria, a Greek engineer who worked in the arsenal of Rhodes in the 3rd century BCE. It wasn’t a crossbow in the traditional sense but used a torsion mechanism based on bundles of twisted sinew, and we only know about it from the description left by Philo of Byzantium, who wrote between 280 and 220 BCE.
Philo recounts how one of these weapons was found and provided a detailed description of the gears that powered a chain drive to position bolt after bolt into its firing groove. This is the earliest known application of such a mechanism.
The study published in the Nexus Network Journal focuses on a section of the northern wall of Pompeii near the gates of Vesuvius and Herculaneum, where the researchers, led by Adriana Rossi from the University of Campania, found and analyzed small holes in the stones.
These marks are square or diamond-shaped and do not match the impact patterns of stones launched by conventional catapults. Instead, they appear to have been caused by arrows or metal projectiles.
They appear in groups of four or five, as if the projectiles that caused them had been fired in bursts, something difficult to achieve with handheld weapons or traditional crossbows.
The precision and frequency suggest the use of a repeating machine, the researchers assert, believing that they could be the work of a polybolos used during the siege of Pompeii in 89 BCE, when the troops of the Roman general Sulla conquered the city. Although no physical remains of the weapon have been found, the markings on the walls would match its historical description.
To confirm their theory, the team used 3D scanning techniques and digital reconstructions. Through virtual models, they calculated the speed and force of the impacts, estimating that the arrows that could have made the marks reached a speed of around 109 meters per second, a rather surprising speed for the time. They also confirmed that the depth and shape of the holes matched models of Roman arrowheads kept in European museums.
Why Shoot Arrows at the Walls?
But why would the Roman army besieging the city have fired arrows at the stone walls instead of at the defenders? The researchers offer two fairly evident theories.
The first is that they simply missed their shots—that is, they were aiming at soldiers on top of the wall but missed, perhaps because the weapon was hard to handle or simply wasn’t as effective as it should have been.
And the second is that they were simply testing, practicing and calibrating the polybolos before using it against the enemy.
In this regard, an episode of the popular show MythBusters aired in 2010 built and fine-tuned a replica of the polybolos based on Philo’s description, concluding that its existence as a historical weapon was plausible, despite being prone to constant mechanical failures.
The team now plans to analyze more sections of the walls of Pompeii and collaborate with museums to cross-reference their findings. They also hope this discovery will attract interest to Pompeii not just as a city frozen in time, but also as a battlefield where Roman military engineering left its mark.
SOURCES
Rossi, A., Gonizzi Barsanti, S. & Bertacchi, S. Use of Polybolos on the City Walls of Ancient Pompeii: Assessment on the Anthropic Cavities. Nexus Netw J 27, 243–272 (2025). doi.org/10.1007/s00004-024-00803-x
Reconstruction of a polybolos. Credit: Diels and Schramm 1919 / AR and archives of Archeotecnica / archeotecnica.com