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.
It remained their headquarters until at least 300 AD.
The interior was fitted out with the usual array of military buildings: a headquarters building, legate's residence, tribunes' houses, hospital, large bath house, workshops, barrack blocks, granaries and, unusually, a large amphitheatre..
At this time there were four legions in Britain out of a total of about 30 legions in the Empire, making Britain one of the most heavily militarised provinces due to its frontier status and hostile neighbours.
Each legion consisted of over 5,000 heavily armed and highly disciplined professional soldiers who enlisted in the army for at least 20 years.
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.

An inscription of Trajan gives a date of AD99/100 for the replacement of the fortress walls, when the original earth 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 rebuilding themselves after heavy losses on the Continent.
Further restoration took place under Caracalla, when the south-west gate was rebuilt, the amphitheatre remodelled and barrack blocks re-roofed and otherwise repaired.
The legion may have been called away to fight for one of the many emperors claiming power in the late 3rd century.
Although most of the fort lay empty, a 'caretaker' squad are thought to have maintained the facilities and there was reoccupation and rebuilding work as late as the 270s.
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.
The stone from Isca may have been used for building defences on the south coast.
There may still have been an occasional military presence as late as the early 4th century, but the fortress was probably later taken over by the people of the surrounding vicus.
The basilica of the baths was used as a cattle pen.

Recent finds suggest Roman occupation of some kind as late as 380.
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. It remained their headquarters until at least 300 AD. The interior was fitted out with the usual array of military buildings: a headquarters building, legate's residence, tribunes' houses, hospital, large bath house, workshops, barrack blocks, granaries and, unusually, a large amphitheatre..
At this time there were four legions in Britain out of a total of about 30 legions in the Empire, making Britain one of the most heavily militarised provinces due to its frontier status and hostile neighbours. Each legion consisted of over 5,000 heavily armed and highly disciplined professional soldiers who enlisted in the army for at least 20 years. 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.
An inscription of Trajan gives a date of AD99/100 for the replacement of the fortress walls, when the original earth 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 rebuilding themselves after heavy losses on the Continent. Further restoration took place under Caracalla, when the south-west gate was rebuilt, the amphitheatre remodelled and barrack blocks re-roofed and otherwise repaired. The legion may have been called away to fight for one of the many emperors claiming power in the late 3rd century. Although most of the fort lay empty, a 'caretaker' squad are thought to have maintained the facilities and there was reoccupation and rebuilding work as late as the 270s. 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. The stone from Isca may have been used for building defences on the south coast. There may still have been an occasional military presence as late as the early 4th century, but the fortress was probably later taken over by the people of the surrounding vicus. The basilica of the baths was used as a cattle pen.
Recent finds suggest Roman occupation of some kind as late as 380.
Isca Augusta