Headquarters of the Legion "II Augusta", which took part in the invasion under Emperor Claudius in 43, Isca is uniquely important for the study of the conquest, pacification and colonisation of Britannia by the Roman army.

Excavations continue to unearth new discoveries;[1] in the late 20th century a complex of very large monumental buildings outside the fortress between the River Usk and the amphitheatre was uncovered.

Isca was founded in 74 or 75 during the final campaigns by Governor Sextus Julius Frontinus against the fierce native tribes of western Britain, notably the Silures in South Wales who had resisted the Romans’ advance for over a generation.

Isca became the headquarters of the Legion II Augusta based in the large fortress of typical legionary "playing-card" shape and built initially with an earth bank and timber palisade.

As the backbone of the army, legionaries were the conquerors and builders of the Roman Empire who brought with them foreign ideas, practices and traditions that would change the society and culture of Britain forever.

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.

The main military structures are thought to have finally been demolished by the usurpers, Carausius or Allectus, when the legion was needed to repel a potential invasion from the Continent.

He writes: God, therefore, who wishes all men to be saved, and who calls sinners no less than those who think themselves righteous, magnified his mercy towards us, and, as we know, during the above-named persecution, that Britain might not totally be enveloped in the dark shades of night, he, of his own free gift, kindled up among us bright luminaries of holy martyrs, whose places of burial and of martyrdom, had they not for our manifold crimes been interfered with and destroyed by the barbarians, would have still kindled in the minds of the beholders no small fire of divine charity.

[9] The arena is oval in shape, with eight entrances, and the stadium is thought to have had a capacity of around six thousand spectators, and apart from the usual gladiatorial entertainments, it was probably used for parades, displays and exercises by the garrison of the fortress.