The extensive remains of the legionary fortress at Caerleon are one of the largest and most important Roman military sites in Europe. The fortress at Caerleon was established around AD 75 as the headquarters of the Second Augustan Legion, Legion II Augusta. The legionary fortress of Isca took its name from the nearby river Usk, where on a flat site, close to where ships could land supplies, the fortress was laid out with characteristic Roman efficiency to a text book plan. The defences, built first of earth and timber but replaced in stone about AD 100, enclosed an area of about 50 acres. Inside the defences most of the buildings were constructed in wood, but from the second century they were gradually rebuilt in stone. At the centre of the fortress, was the headquarters building- the principa. More than half of the remaining area was given over to barrack blocks, but there were also officers? houses, a hospital, the fortress baths and various storerooms and workshops to provide the essential support services for the 5,500 fighting men that made up Legio II Augusta. Around AD 90, just outside the south-west defences of the fortress, the legion was provided with an amphitheatre, where gladiatorial combats and weapon training took place. The fortress flourished for over two hundred years and a thriving civilian settlement grew up around the defences and across the river Usk. By AD 300 Legio II Augusta had left Isca due to political and economic problems that lead to the redeployment of troops and the gradual disintegration of Western Roman Empire. As a result, many of the main fortress building were demolished.

Source: Knight, J.K. 2003. Caerleon Roman Fortress: CADW

M. Lloyd Davies, RCAHMW, 22 October 2008