Vallum

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A vallum was a type of palisade, used as part of the Roman defensive fortification system. It was usually made out of earth, sometimes enforced with wood and stone, and also had a deep moat (fossa).

It is derived from vallus ^[1] (a stake), and properly means the palisade which ran along the outer edge of the top of the agger, but it very frequently includes the agger also. The vallum, in the latter sense, together with the fossa or ditch which surrounded the camp outside of the vallum, formed a complete fortification.

Characteristics

The valli (χάρακες), of which the vallum, in the former and more limited sense, was composed, are described by Polybius (xviii.18.1, Excerpt. Antiq. xvii.14) and Livy (Liv. xxiii.5), who make a comparison between the vallum of the Greeks and that of the Romans, very much to the advantage of the latter. Both used for valli young trees or arms of larger trees, with the side branches on them; but the valli of the Greeks were much larger and had more branches than those of the Romans, which had either two or three, or at the most four branches, and these generally on the same side. The Greeks placed their valli in the agger at considerable intervals, the spaces between them being filled up by the branches; the Romans fixed theirs close together, and made the branches interlace, and sharpened their points carefully. Hence the Greek vallus could easily be taken hold of by its large branches and pulled from its place, and when it was removed a large opening was left in the vallum. The Roman vallus, on the contrary, presented no convenient handle, required very great force to pull it down, and even if removed left a very small opening. The Greek valli were cut on the spot; the Romans prepared theirs beforehand, and each soldier carried three or four of them when on a march (Polyb. l.c.; Virg. Georg. iii.346, 347; Cic. Tusc. ii.16). They were made of any strong wood, but oak was preferred.

A fortification like the Roman vallum was used by the Greeks at a very early period (Hom. Il. ix.349, 350).

Usage

In the operations of a siege, when the place could not be taken by storm, and it became necessary to establish a blockade, this was done by drawing defences similar to those of a camp around the town, which was then said to be circumvallatum. Such a circumvallation, besides cutting off all communication between the town and the surrounding country, formed a defence against the sallies of the besieged. There was often a double line of fortifications, the inner against the town, and the outer against a force that might attempt to raise the siege. In this case the army was encamped between the two lines of works.

Construction

Vallum at Hadrian's Wall near milecastle 42

This kind of circumvallation, which the Greeks called ἀποτειχισμός and περιτειχισμός, was employed by the Peloponnesians in the siege of Plataea (Thucyd. ii.78, iii.20‑23). Their lines consisted of two walls (apparently of turf) at the distance of 16 feet, which surrounded the city in the form of a circle. Between the walls were the huts of the besiegers. The walls had battlements (ἐπάλξεις), and at every ten battlements was a tower, filling up by its depth the whole space between the walls. There was a passage for the besiegers through the middle of each tower. On the outside of each wall was a ditch (τάφρος). This description would almost exactly answer for the Roman mode of circumvallation, of which some of the best examples are that of Carthage by Scipio (Appian, Punic. 119, &c.), that of Numantia by Scipio (Appian, Hispan. 90), and that of Alesia by Caesar (Bell. Gall. vii.72, 73). The towers in such lines were similar to those used in attacking fortified places, but not so high, and of course not moveable. (Lipsius, de Milit. Rom. v.5, in Oper. iii. pp156, 157; Poliorc. ii.1, in Oper. iii.283).

The vallum-building technique was later taken by neighbouring people, such as the Byzantines and the Goths.

Examples

Examples of valla include:

• Hadrian's Wall (England, Roman)
• Trajan's Wall (Romania, Byzantine Age)
• Athanaric's Wall (Romania, Moldova, 2-4th century, probably made by the Goths)

Etymology

1. ^  Latin vallus derives from Proto-Indo-European *walso-, " a post". Vallus is the source of English wall.

The word vallus is sometimes used as equivalent to vallum (Caesar, Bell. Civ. iii.63).

References

• "A Dictionary of Greek and Roman Antiquities". William Smith, LLD. William Wayte. G. E. Marindin. Albemarle Street, London: John Murray, 1890.

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