Defense of Ancient Rome

Ancient Rome was defended first by the Servian Wall and then by the Aurelian Walls each had fortified Gates.
During the Empire, the defending Army initially consisted of several cohorts of the Praetorian Guard, and later an entire legion, the Legio II Parthica.

Praetorian Guard:
- 23-312 CE Created by Augustus and Disbanded by Constantine I.
- Located in the Praetorian Barracks (Castra Praetoria), which was built between 21-23 CE on the North East Wall.
Legio II Parthica:
- c.198-c.312 CE. Introduced by Septimius Severus and later moved to the East by Constantine I, they were located in the Castra Albana 198-312 CE at Albano Laziale, 15 miles (25 km) from Rome. After 312 CE, the Legion was moved to Mesopotamia.

Servian Wall
- This was Rome’s first defensive wall, built after the first Sack of Rome in 390 BCE.
Aurelian Walls
- Built by Aurelian between 270-275 CE, the much longer Aurelian Walls were added, to a greatly expanded Rome. This was to meet the threat of the Germanic Invasions.
Pomerium
- This was the Sacred Boundary of Rome, which extended every time the Empire was expanded.

Praetorian Guard (Cohors Praetoria)
- Three Cohorts were garrisoned in the Castra Praetoria, acting as the Emperor’s personal bodyguard and present at all official events.
Cohortes Urbanae (Urban Cohorts)
- Three Cohorts acted as a Police force for Rome, under the city Prefect, the Praefectus Urbi.
- They were garrisoned with the Praetorian Guard in the Castra Praetoria.
Vigiles Urbani (Vigiles)
- These were the Firefighters and nightwatchmen for the city.
- They were organised into 7 Cohorts, each with a Tribune, all commanded by a Praefectus Vigilum of Equestrian rank. Drawn from Freedmen, they were not soldiers but were still organised along military lines. Each Cohort controlled two of Rome’s 14 regions.
Legio II Parthica
- Septimius Severus moved this Legion into the Castra Albana, Rome in 198 CE, and they stayed until Constantine I removed them in 312 CE.