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Roman camp (singular: castrum Romanum, castra romana, castra Romanorum – “camp of the Romans”) was distinguished by its excellent workmanship. What is worth emphasizing, it was not built by professional engineers and builders, but by ordinary legionnaires. The main building material was wood. The camp was established every day during the campaign.
It seems certain that the legionaries were undergoing special training to practice the construction of such a camp. If necessary, they had to be able to set it up quickly and efficiently. Proof of the existence of training camps is the remains of such facilities in western Germany (North Rhine-Westphalia state). According to ancient sources, the average time for erecting a Roman camp was between 4 and 5 hours. In favourable conditions, it could be erected even in 3 hours.
The fortified Roman camp was either square or rectangular, surrounded by a wall with four gates and a rampart or palisade. Corners of castrum were rounded to make it difficult for enemies to climb the palisade. The camp, which was the seat of legionaries during the winter, was referred to as hiberna.
Romans had certainly built fortified camps during the war with Pyrrhus in 280-275 BCE. Those were built every night to shelter the army in the event of a lost battle or leaving rolling stock and wounded during the battle.
Construction usually began in the afternoon, because the army’s daily timetable was arranged by the hour. Very early in the morning (when the sun rose) the legionaries set off. The journey took 8 hours on average. A special group was sent in front to choose the best place to build the camp and begin preparations for construction. After a constant march, the legionaries stopped in a convenient place for the camp and divided into groups:
- bringing wood and building material
- construction
- material storage and transport to the site
- patrolling and protecting the workplace
As Vegetius, a late Roman writer points out, the construction of the camp was extremely important.
Recruits are to be instructed in the manner of entrenching camps, there being no part of discipline so necessary and useful as this. For in a camp, well chosen and entrenched, the troops both day and night lie secure within their works, even though in view of the enemy.
– Vegetius, De Re Militari
Establishment of the camp
According to Polybius, the place for the camp was chosen by tribunes and centurions. First, the location for the command tent was marked out; then straight lines were drawn around this tent, which marked out the space on which the tents of the tribunes would stand, and then of the legion. Distances were carefully measured and marked on the ground with flags of different colours. When the main forces arrived at the site, the soldiers had a clear view of the layout of the camp and construction work began.
When the commander stopped and work began on the camp, auxiliary units were sent to plunder the area (enemy territory) or to obtain food, feed and wood for bonfires. Legionaries extracted tools from their backpacks and built a fortified camp. It is worth noting that the most frequently chosen place for the creation of the camp were hills, for defensive and scenic reasons. In addition, the camp should be located facing the slope, if possible close to the forest and water source – minimizing the possibility of an ambush. The area was cleaned and levelled.
When the legionaries dug the ground, one cohort from each legion stood guard. The rampart near the moat was built from the soil recovered in this way. The embankment is usually measured, as described by Polybius, 4 meters high and 1 meter wide, and equal to 4 meters wide and 3 meters deep. Julius Caesar reportedly had a penchant for embankments over 6 meters wide.
Construction began with defensive elements. Cut-down trees were used for gates (about 15 meters wide) and watchtowers, which, after being constructed on-site, were placed on each of the four embankments (all of them were to be burnt the next day when the army set off on the road). The firing forces were located along with the forecast. The space of 60 meters between ramparts (agger) and the first rows of tents were filled with cattle, booty and prisoners of war. It was a so-called intervallum. As Polybius writes, they were placed here so that in the event of an enemy attack one could not reach them with fiery arrows. This space protected leather and canvas tents and wooden buildings against enemy shots and attempted to set the camp on fire during the siege. Thus, the embankment (agger) was built and a palisade (vallum) was built, which together with the excavation (fossa) surrounding them surrounded the whole camp. intervallum was left between the camp ramp and the soldiers’ tents.
The height of the camp wall was usually two-thirds of the width of the ditch, the width was similar. The slope and wall surrounding the camp were always crowned with a palisade (vallum).