Roman Siege Warfare

Siegecraft and Artillery in the Roman Empire

Dec 21, 2008 Robert Marcell

Roman soldiers excelled at siege warfare. They employed a variety of clever strategies, powerful devices, and elaborate techniques to break into fortified towns.

Before the rise of the medieval castle, the strongest fortification normally encountered by an invading army was the fortified city or town. The earliest example of a fortified town in the archaeological record dates back to 2700 B.C.E. with the town of Uruk, in present-day Iraq (Gabriel, 123). Walled towns go back even earlier, with examples like Jericho, but these may not have been fortified for military purposes. By the time of the Romans, fortified cities and towns were common.

The Roman ability to successfully besiege fortified positions was the best in the ancient world, but, according to Richard Gabriel, "it relied primarily on organization and application rather than on engineering innovation." (127) Many of the devices that the Romans came to rely upon for the conduct of their sieges originated in ancient Greece and Persia, and were simply improved upon by the Romans (127).

Nevertheless, the combination of adapted technology, military innovation, and Rome's seemingly indefatigable determination for victory made the Romans masters of siege warfare.

Circumvallation and Countervallation

The circumvallation (or investment) of a fortified position is, essentially, the military tactic of surrounding a position to prevent the freedom of movement into or out of the position. The Romans extended this basic principle with countervallation, or bicircumvallation, whereby they set up one line of fortifications to keep people inside of a city, and also a connected line of counterfortifications behind themselves to prevent an attack from those who might try and lift their siege (Cross, 44).

Surrounding an enemy in this manner allowed for a blockade, and the Romans were patient enough to starve their opponents into surrendering. To encourage their opponent to surrender, they might also poison the town's water supplies (Shelton, 257).

The most famous example of bicircumvallation in action is Caesar's siege of Alesia, in 52 B.C.E., during the Gallic Wars. At Alesia, Caesar enclosed the leader of the Gauls, Vercingetorix, and his 80,000-strong army with a double line of fortifications. Vercingetorix and the relief force that came to save him could not coordinate their attacks on the Roman fortifications, and Vercingetorix was forced to surrender (Cross, 34).

Siegecraft

The Romans employed a great variety of siege engines. These included:

The Battering Ram: The battering ram was usually a long, wooden beam with an iron tip on the end. It was suspended by ropes from a sturdy, mobile frame called a "tortoise," which protected the soldiers operating the ram from enemy missile attack (Cross, 44).
The Siege Tower: The Romans also relied on armored siege towers, some as high as 24 meters (75 feet), which could be wheeled towards a city's walls (Gabriel, 127). They were primarily used as raised platforms for assaults or missile attacks, and were iron-plated or covered in layers of wet wicker and hide to proof them against fire and bombardment. The lower-level of a siege tower often incorporated a battering ram, so that the gates could be battered open while archers kept the walls cleared (Cross, 44).
Miscellaneous Devices: The Romans used an assortment of other devices, including, "large iron hooks to dislodge stones; covered platforms to protect miners and assaultteams; and bridges, drawbridges, and elevators mounted on towers to swing assaultteams over the walls." (Gabriel, 127)

The Romans might also mine beneath a targeted city's walls, usually to weaken the walls by setting fire to the mine's supports and causing the earth beneath the walls to collapse with the mine. They would even sometimes divert a stream into the city or under the walls to cause flooding (Shelton, 257).

Artillery

Roman artillery was the largest, longest-ranged, and most rapidly firing artillery in the ancient world (Gabriel, 128). They threw stones or fired arrows using torsion devices and springs, and included:

The Onagi: Rome's largest catapults, thought to be developed in the third century C.E., could throw stones weighing up to 45 kg (110 lb) over 400 yards. These were called onagi (singular onager), or "wild asses," because of their recoil, which reminded the Romans of the kick of a donkey or mule (Gabriel, 128).
The Ballistae: Smaller catapults called ballistae were light enough to be transported by horse when disassembled, and could fire either stone shot or javelins (Gabriel, 128).
The Scorpion: A controversial device that some historians claim fired bolts like a standing crossbow, while others insist it was more like a catapult.
The Carroballistae: Smaller machines, perhaps including the scorpions, fired iron-tipped bolts. But the largest of these javelin or bolt-throwing machines was the carroballistae, mounted on a wheeled frame and requiring a ten-man crew, which could fire 3-4 bolts a minute -- the world's "first rapid-fire field artillery guns" (Gabriel, 128).

All in all, the Roman achievement with siegecraft and artillery is impressive. Not only were theirs the greatest besieging armies of their day, but, as Richard Gabriel notes, the "rate of fire of Roman field artillery was not surpassed until the invention of the breach-loading artillery gun firing fixed ammunition at the end of the American Civil War." (Gabriel, 128)

Sources

Cross, Robin (Editor). The Encyclopedia of Warfare: The Changing Nature of Warfare from Prehistory to Modern-day Armed Conflicts. Barnes & Noble: New York, 2006.

Gabriel, Richard A. Soldiers' Lives through History: The Ancient World. Greenwood Press: Westport, Connecticut, 2007.

Holmes, Richard (Editor). The Oxford Companion to Military History. Oxford University Press: Oxford, 2001.

Shelton, Jo-Ann. As the Romans Did: A Sourcebook in Roman Social History (2nd Edition). Oxford University Press: Oxford, 1998.

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