The Roman army used these defensive camps, called castra, very often,
sometimes letting opportunities for battle slip to be able to finish their camp.
A simple castrum consisted of a low earthen rampart with wooden palisade on top, surrounded by a ditch.
Engineers would supervise the building, but the common soldiers had so much experience in setting up camps
that a Roman force could build a basic castrum in a few hours.
If the army stayed put for more than one night, the castrum would often be strengthened with higher walls and the addition of watchtowers.
A Roman castrum for a large force had a strict rectangular layout with 2 main roads crossing it, a gate on each edge
and predetermined locations for tents of officers and men, stables, supply storage, workshops, hospital and even baths.
When an army stayed in one place for a long time, castra would be upgraded by expanding ditches to full-sized moats, erecting stone walls, watchtowers and gatehouses,
so that they became modest fortresses.
The castra of garrisons were such permanent constructions that they often ended up forming the basis of towns, with the same rectangular grid street pattern as the castra.
Only the Romans built temporary fortified camps frequently; other armies mostly disdained them, except during sieges.
War Matrix - Fortified camp
Greek Era 330 BCE - 200 BCE, Weapons and technology