Roman conquest of Anglesey

• 1. Introduction

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  Anglesey sits off the northwest coast of Wales, separated from the mainland by a narrow tidal channel called the Menai Strait. To most Roman commanders in the 1st century CE, it was a distant and difficult target at the far edge of the known world. To Suetonius Paulinus, the governor of Britannia, it was something more urgent: a sanctuary for enemies of Rome, a sacred centre for the Celtic Druids, and a problem that could not wait. What happened when his forces finally reached that churning stretch of water in 60 CE would become one of the strangest scenes recorded from Roman Britain. And what they found when they reached the other shore would test their nerve in ways that no military manual could have prepared them for. The island would be invaded twice, occupied for more than three centuries, and yet leave almost no trace of the Roman world behind. How is that possible? And why, after all that time, did Anglesey remain so stubbornly itself?

• 2. The Druid Island

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  Tacitus, writing of Suetonius Paulinus, is direct about his motives. Britain, Tacitus says, had come "to be in the hands of Suetonius Paulinus," who aspired to rival the military glory of Corbulo by subjugating Rome's enemies. Anglesey, recorded in Latin as Mona, had what Tacitus called "a powerful population" and was a refuge for those fleeing Roman rule across Britain. The decision to invade may also have been sharpened by knowledge of copper mines on the island, though the strategic pull of a Druid stronghold was itself enough. The Druids were not merely priests. They were the custodians of a cultural and political identity that Rome found both threatening and incomprehensible. Tacitus records that their altars ran with the blood of captives and that they consulted their gods through human entrails. Whether this was accurate Roman intelligence or hostile propaganda, it was the image that drove Roman policy. No sacred groves from this period have been confirmed by archaeology on Anglesey itself, but late Iron Age ritual deposits have been found at a small lake called Llyn Cerrig Bach, on the other side of the island, pointing to the depth of religious practice there.

• 3. Crossing the Strait

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  The Menai Strait presented Suetonius Paulinus with a real tactical problem. The channel runs roughly 8 km long, with tidal currents reaching up to 7.5 knots in its narrower and rockier sections. Timing a mass crossing on those waters required, as the source notes, at least a long enough period of observation to predict the tides with reasonable accuracy. Tacitus tells us Paulinus solved the infantry problem by constructing flat-bottomed vessels suited to shallows and uncertain depths. The cavalry swam alongside their horses where the water ran deep, and forded where it did not. The precise crossing point remains unknown. William Manning, among modern scholars, suggested the northeastern end of the Strait near the present city of Bangor, where medieval travellers once crossed by ferry over the Lavan Sands. At low tide, the sea crossing there narrows to roughly 240 metres. A landing near the parish of Llanidan, further southwest, would have offered calmer currents and gentler slopes up from the shore, though a longer sea crossing. Field names in Llanidan parish recorded in 1867, "Maes Hir Gad" meaning area of long battle, and "Cae Oer Waedd" meaning field of cold or bitter lamentation, have been suggested as possible markers of a Roman attack, though which invasion they may reference remains uncertain.

• 4. Fear on the Shore

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  Tacitus describes what the Roman soldiers saw when their boats ground onto the Anglesey shore. A dense line of armed warriors faced them. Between the ranks ran women dressed in black like the Furies, their hair dishevelled, carrying burning brands. Around them, Druids lifted their hands toward the sky and poured out what Tacitus calls "dreadful imprecations." The effect on the Roman soldiers was, by any standard, remarkable. Professional soldiers trained to face organized military formations stood motionless and exposed to wounds, as if their limbs were paralysed. Tacitus himself notes that Roman soldiers are not often described as scared to paralysis, and that their reception must have been an extraordinary experience even for veterans. The rally came when their general urged them not to quail before what he called a troop of frenzied women. They advanced, drove back the defenders, and destroyed the sacred groves they found. The brutality of the conclusion is typical of Roman accounts of conquest at the edges of empire. What followed, though, was not a settled occupation. The news that arrived from southern Britain changed everything.

• 5. Boudica's Shadow

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  Suetonius Paulinus had barely begun garrisoning Anglesey when word reached him of the Boudican revolt erupting to the south. Tacitus records his reaction tersely: with "wonderful resolution" the governor marched through a hostile population to Londinium. The island was abandoned. It would remain free of Roman rule for sixteen years. Between the two invasions, five governors came and went in Britannia, and none attempted a new campaign in Wales. The Roman world was in a period of internal strain, with military conflicts across the Empire, unrest in the British legions, and the long shadow of Boudica's rebellion pressing against further expansion. Only with Vespasian's accession to emperor in 69 CE did the wider conquest of Wales resume. Julius Frontinus arrived as governor in 74 CE and subdued the Silures tribe in South Wales, according to Tacitus in a single sentence. It was Frontinus's successor who would finally return to Anglesey.

• 6. Agricola's Swift Strike

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  Gnaeus Julius Agricola arrived as governor in the summer of 77 CE to find the tribes along the Roman frontier watching him closely. The Ordovices of north Wales had recently destroyed nearly a whole squadron of allied Roman cavalry quartered in their territory. Agricola, rather than waiting out the season, led his forces up a hill against the Ordovices and, in Tacitus's words, "the tribe was all but exterminated." The hillfort Dinas Dinorwig, on a foothill some 3 km from the Menai Strait, has been suggested as possibly connected to this battle; its name is thought to mean fort of the Ordovices. With the mainland victory behind him, Agricola turned his attention to Anglesey. He had no fleet. What he had instead was a unit of auxiliary soldiers, recruited in Britain, with the swimming ability Tacitus describes as a national characteristic. They crossed the strait without boats, without legionaries, carrying their arms and leading their horses. The defenders of Anglesey had been watching for a fleet. They saw none. The sudden appearance of armed men emerging from the water, where no boats had been, broke their resistance entirely. The island surrendered.

• 7. Three Centuries Under Rome

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  The Cemlyn Cropmark is the earliest known Roman military site on Anglesey, dated to around the time of Agricola's invasion in 77 CE. It was discovered in 1990 on an aerial photograph taken during a long dry spell, and a geophysical survey in 2015 confirmed it had the characteristics of a typical Roman fortlet. Partial excavation found two coins: one from the reign of Nerva, one from Hadrian's. The fortlet overlooks Cemlyn Bay, a natural landing point on the island's north coast, and is thought to have served both as a guide for sea-craft and as a policing post. Rome administered Anglesey from Segontium, the fort at present-day Caernarfon on the mainland across the Menai Strait. The island's agricultural life continued with little visible change. At Caer Lêb in the south, a possible farmstead was found with a few rectangular Roman-period buildings outnumbered by traditional round houses nearby. The settlement at Tai Cochion, close to the strait across from Segontium, is the exception: excavation revealed Roman-style corridor housing unlike the circular structures elsewhere on the island. Pottery and coins date its active period to between 100 and 300 CE, and it was probably a civilian trading settlement established shortly after Agricola's conquest. Copper from Parys Mountain had been mined long before the Romans arrived, and roughly 18 round copper ingots, eight carrying Roman stamps, have been found on the island.

• 8. Watching the Sea

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  By the mid-4th century, the character of Roman presence on Anglesey had shifted. The shore-fort Caer Gybi, facing Ireland, was built to secure the island against raiders crossing the Irish Sea. Its walls remain visible today. Around the same period, the hillfort at Parciau contained a dense concentration of population in a defensible location, suggesting that the sense of security that had prevailed for much of the occupation had eroded. A rocky hilltop called Pen Bryn-yr-Eglwys on the island's northwestern corner carries a small square stone platform measuring 9 by 7 metres. It was long assumed to be a chapel ruin, but its position, its size, and three sherds of probable Roman pottery point strongly toward a Roman watchtower. A similar site interpreted as a watchtower has been excavated inside the pre-Roman fort of Caer y Twr on Holyhead Mountain. Direct Roman military control on Anglesey may have ended around 383 CE, when Magnus Maximus drew much of the Britannia garrison to the Continent for his failed bid for imperial power. By 410, when Honorius wrote to the remaining Roman cities in Britain to look to their own defence, no imperial administration remained to appoint officials to the island. Saint Cybi's Church in Holyhead now occupies the site of Caer Gybi; a 12th-century source records that the site was given to Saint Cybi by Maelgwn Gwynedd in the 6th century CE.