Isca Dumnoniorum 28 cities of Britain by the "History of the Britons" as Isca, although Ford read it as a reference to Penselwood and thought it more likely to be Lindinis (modern Ilchester). Isca was also known to the British as Caer Uisc but, after the Roman withdrawal from Britain around 410, there is very little evidence of habitation in Exeter for almost 300 years except for the remains of a building (possibly a church) in the area of the demolished forum and a few nearby graves dated to the 5th, 6th, and 7th centuries. After this, the historical record picks up
Isca Augusta and timber ramparts of the fortress were strengthened by the addition of a stone revetment at the front. This "composite" rampart consisted of a stone wall 5 to 5½ feet thick, backed by a clay bank and fronted by a single ditch By 120 AD, detachments or vexillations of the legion were needed elsewhere in the province and Isca became more of a military base than a garrison. However, it is thought that each cohort still maintained a presence at the fortress. When Septimius Severus seized power in the 190s, he had Isca refurbished and the legion were in residence