Roman Camps

[Nathan Ross]

Stephen Dando-Collins exaggerates, rather (not untypically hock: )

There are several source descriptions of Roman marching camps. Polybius is the most detailed, but he provides no dimensions for the ditches.

Josephus, describing the army in the late first century, reports:

The camp, and all that is in it, is encompassed with a wall round about, and that sooner than one would imagine, and this by the multitude and the skill of the laborers; and, if occasion require, a trench is drawn round the whole, whose depth is four cubits, and its breadth equal.
Josephus Jewish Wars III.5.2

A cubit is approximately one and a half feet - so the ditches are about 6 feet across and deep. Note 'as occasion requires' - implying this wasn't always done!

The military writer known as 'Pseudo-Hyginus' also describes camps (probably second to third century) in De Munitionibus Castrorum. I can't find an english translation readily available, but Smith's Dictionary provides a handy gloss, courtesy of Lacus Curtius:

“The Fossa might be of two kinds, a. The Fossa fastigata, with both sides sloping, so as to form a wedge; or, b. the Fossa Punica, of which the outer side was perpendicular, the inner side sloping, as in the fossa fastigiata. The breadth in either case was to be at least 5 feet... The Vallum was formed of earth and turf, or of stone, 6 feet in height, 8 feet broad.
When the nature of the ground did not admit of the construction of a sufficient vallum, then a cheval-de frise (cervoli) was substituted. When neither a Vallum nor Cervoli could be employed, then the camp was surrounded by a ring of armed men four deep, numerous sentries were posted in each line, and the cavalry patrolled in turn in every direction… when no danger was apprehended, a ditch alone was considered sufficient; and even this was excavated merely for the sake of exercising the men (causa disciplinae).”
From 'Roman Camps' in Smith's Dictionary

Lastly, Vegetius provides details of the (presumably) later Roman army camp:

There are three methods of entrenching a camp. The first is for the case when the army is on the march and will continue in the camp for only one night. They then throw up a slight parapet of turf and plant it with a row of palisades or caltrops of wood. The sods are cut with iron instruments. If the earth is held strongly together by the roots of the grass, they are cut in the form of a brick a foot and one half high, a foot broad and a foot and one half long. If the earth is so loose that the turf cannot be cut in this form, they run a slight trench round the camp, five feet broad and three feet deep. The earth taken from the trench forms a parapet on the inside and this secures the army from danger.
Vegetius – De Re Militari Book III

So it seems there were variations based on terrain and an assessment of local dangers, but a ditch of between 5 and 6 wide and 3 to 6 deep was normal, with either a vallum of appropriate size or some other field defence as a deterrent to attackers.

Gary Brueggeman put together a very detailed website some years ago reconstructing all aspects of the Roman army on the march. It survives as a copy here, if you can live with the pop-ups and adverts:

Brueggeman - Camp Size

- Nathan