A double line of siege fortification: an inner wall (contravallation) to blockade a besieged town and prevent its defenders from escaping, and an outer wall (circumvallation) facing outward to defend the besiegers against a relieving army. Romans had used circumvallation in sieges since the First Punic War, including Scipio Aemilianus's wall and towers around Numantia in 133 BC, but Julius Caesar's siege of the Gallic stronghold of Alesia in 52 BC is the technique's most famous and most extensive application: a double circumvallation roughly 35 kilometres long that let a Roman army of roughly 10 to 11 legions hold off both a besieged Gallic garrison and a much larger Gallic relief force at the same time.
Facts
Core ClaimEncircle a besieged stronghold with an inner wall to blockade its defenders, and build a second, outward-facing wall beyond it to defend against a relieving army, so a besieging force cannot be attacked from both sides at once. 1 Origin YearMarks Caesar's siege of Alesia, the doctrine's most extensive and best-documented application; the underlying technique of walling off a besieged town was already in Roman use over a century earlier, at Numantia in 133 BC and in the Punic Wars sieges of Agrigentum and Lilybaeum. Cross-Tradition Connections
Associated With
Alesia is this atlas's own specific entry for Caesar's double-wall method.
Developed By
Caesar directed this specific double-wall construction at Alesia; the general technique of circumvallation and contravallation was already established Roman siege practice before him (see entity description).
Sources
1. Wikipedia: Battle of Alesia
WikipediaSiege sectionQuote, Siege section
Caesar ordered the construction of an encircling set of fortifications, a contravallation, around Alesia...To prepare for the arrival of the Gallic relief forces, Caesar constructed an outer fortification (a circumvallation).
1. Wikipedia: Battle of Alesia
World History Encyclopedia: Roman Siege Warfare
World History EncyclopediaFamous Sieges and Numantia sectionsQuote, Famous Sieges and Numantia sections
A notable Roman siege was carried out by Julius Caesar at Alesia in 52 BCE, more strictly speaking a blockade, where he built a double circumvallation measuring 35 km...In 133 BCE Scipio, this time, lay siege to Numantia in Spain by building a ditch and stone wall punctuated by towers around the entire town.
Wikipedia: Siege
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