Anglesey, which was recorded in Latin as Mona and is still known as Môn in modern Welsh, was a place of resistance to Roman rule because it was an important centre for the Celtic Druids and their religious practices. The Roman conquest of Anglesey refers to two separate invasions of Anglesey in North West Wales that occurred during the early decades of the Roman conquest of Britain in the 1st century CE. The first invasion of North Wales began after the Romans had subjugated much of southern Britain. It was led by the Provincial governor of Britannia, Suetonius Paulinus, who led a successful assault on the island in 60–61 CE, but had to withdraw because of the Boudican revolt. In 77 CE, Gnaeus Julius Agricola's thorough subjugation of the island left it under Roman rule until the end of Roman rule in Britain in the early 5th century CE.
No surviving Roman sources mention Anglesey after the conquest. Archaeologists have located a fort dated shortly after the first conquest near Cemlyn Bay; a trading settlement on the shore of the Menai Strait; and a village of huts huddled together on a hill for defence. In the last decades of Roman rule in Britain several military forts were built on the northern and western coasts to defend the island against Irish sea raiders. However, despite more than three centuries of Roman rule, archaeologists have found no evidence of major civic centres or villas on the island indicating that Romano-British culture lacked the influence it had in other parts of the Roman province of Britannia.
The only Roman source for the island's two invasions is the Roman historian Tacitus. His last work The Annals, written as a history of the Roman Empire from Tiberius until Nero, mentions the first invasion by Suetonius Paulinus. The second invasion is detailed in Tacitus' work The Life of Gnaeus Julius Agricola, which was written to record and extol the life and accomplishments of his father-in-law. Tacitus may have used first-hand accounts from Agricola, who had been present with the Roman forces on both occasions.
First invasion (60 CE) The first invasion of Anglesey took place in 60 or 61 CE following Suetonius Paulinus' success in other parts of the province, subjugating British tribes and establishing Roman forts. Tacitus writes: "Britain was in the hands of Suetonius Paulinus, who in military knowledge and in popular favour, which allows no one to be without a rival, vied with Corbulo, and aspired to equal the glory of the recovery of Armenia by the subjugation of Rome's enemies. He therefore prepared to attack the island of Mona which had a powerful population and was a refuge for fugitives." Tacitus, who later married the daughter of Suetonius Paulinus's young aide-de-camp, Gnaeus Julius Agricola, may have heard first-hand accounts of the campaign and even of Suetonius's personal comments.
The decision to invade may also have been motivated by information about copper mines on Anglesey.
Approaching the Menai Strait
Tacitus says: "[Suetonius Paulinus] built flat-bottomed vessels to cope with the shallows, and uncertain depths of the sea. Thus the infantry crossed, while the cavalry followed by fording, or, where the water was deep, swam by the side of their horses."
He does not state where these boats were built, perhaps Deva Victrix (Chester), where a few pre-Flavian coins may indicate an early base whose role would have been tied to the movement of troops by sea along the coasts of north Wales.
Marshy ground to the west of Chester made it a poor base for overland penetration of North Wales, and Suetonius' march to the Menai Strait may have used the oldest known crossing of the River Dee, some 13 km south of Chester at Holt. An army moving on foot along the north coast of Wales would have first seen Anglesey from the mouth of the Sychnant Pass near Abergwyngregyn, where the three land routes converge.
Crossing the Menai Strait
The Roman forces then had to cross the Menai Strait, a narrow strip of water some 8km long that separates the island of Anglesey from the rest of the Welsh mainland. The sea crossing would be short and relatively easy at slack water, but at full strength the tidal currents can be up to 7.5 knots with much turbulence in the narrower and rockier sections. Local knowledge, at least a long enough period of observation to predict the tidal currents with reasonable accuracy, would be required to plan safe transit. (The later invasion under Agricola took the natives by surprise because they had expected to see a fleet in plenty of time to gather for their defence of the island.)