A Guide to the History of Welsh Castles: Conquest, Resistance and Legacy

Written by Simon Williams

Wales is a land of castles. More than 600 of them, in various states of preservation, dot the landscape, making it one of the most castle-dense regions in Europe. They rise above rivers and coastlines, from the stone towers of Edwardian masterpieces to crumbling motte-and-bailey earthworks. Each one tells a story of conquest, resistance, and the struggle to control a land that never surrendered easily.

The First Castles: Norman Conquest and the March

The castle-building story in Wales begins with the Norman Conquest of England in 1066 and the subsequent push into Welsh territory. William I established powerful Marcher lords along the border, granting them almost royal authority in exchange for the hazardous work of advancing into Wales. These lords, men like Roger of Montgomery and William FitzOsbern, built the first castles in Wales: motte-and-bailey earthworks thrown up quickly to secure newly seized land.

Chepstow Castle, begun in 1067, is one of the earliest surviving stone structures in Wales and among the oldest in Britain. Its position above the River Wye, just inside the Welsh border, made it a gateway to conquest. Over the following century, the Marcher lords pushed steadily westward, their castles marking the advancing line of Norman power.

These were not decorative buildings. They were working instruments of control, housing garrisons, administering justice, and demonstrating to the native Welsh population that their conquerors had come to stay.

Native Welsh Castles

The Welsh princes did not simply accept the new architecture of power. They adopted it. By the twelfth century, native Welsh rulers were building stone castles of their own, using the same technology their enemies had introduced to defend their own territories.

Dolwyddelan Castle in Snowdonia, traditionally associated with the birth of Llywelyn ap Iorwerth (Llywelyn the Great), represents the native Welsh tradition: a simple rectangular tower on a rocky outcrop, built for defence rather than display. Criccieth Castle, developed by both native princes and later English rulers, shows how the same site could serve successive waves of power.

The Welsh princes also understood the strategic logic of castle building. Control of key passes through Snowdonia and river crossings across Wales could deny an invading army its momentum. Native castles were therefore positioned to exploit Welsh geographical advantages: the mountains, the narrow valleys, the rivers that could become obstacles to a heavy cavalry force.

The Age of Llywelyn and the Height of Welsh Power

The thirteenth century saw the Welsh principality reach its greatest extent under Llywelyn ap Iorwerth and his grandson Llywelyn ap Gruffudd, known as Llywelyn the Last. The latter secured recognition as Prince of Wales from the English crown through the Treaty of Montgomery in 1267, a remarkable achievement that represented the high point of Welsh political autonomy in the medieval period.

During these years, Welsh castle building intensified. Dolbadarn Castle, commanding the pass of Llanberis in Snowdonia, was developed as a key stronghold. Bere Castle in Merioneth guarded the approaches to the Welsh interior. These castles were intended not merely as military assets but as statements of sovereignty, the physical expression of a Welsh polity that could stand alongside the kingdoms of England and France.

Edward I and the Ring of Iron

The death of Llywelyn ap Gruffudd in 1282 and the subsequent defeat of his brother Dafydd marked the end of Welsh political independence. What followed was the most ambitious castle-building programme in British history.

Edward I understood that military victory was insufficient without permanent control. His solution was a network of massive fortresses stretching across north Wales, designed by the Savoyard master builder James of St George. Conwy, Caernarfon, Harlech, Beaumaris: these were not merely castles. They were integrated systems of control, each paired with a walled English town that would provide settlers, commerce, and a permanent English presence in the conquered territory.

The scale of the investment was extraordinary. Edward spent approximately £80,000 on his Welsh castles between 1277 and 1330, a sum equivalent to several years of English royal income. Caernarfon Castle alone, with its distinctive banded stonework and polygonal towers deliberately echoing the walls of Constantinople, was designed to be a statement of imperial ambition.

The Statute of Rhuddlan in 1284 gave the castle network its administrative teeth, imposing English law on Wales and creating a system of English counties under royal control. The castles became headquarters of this new administration, housing sheriffs and officials who extended the reach of English governance into every corner of Welsh territory.

Resistance and the Castles' Later History

The Edwardian castles were built to last, and they were tested. The revolt of Madog ap Llywelyn in 1294–95 briefly captured Caernarfon, demonstrating that even the greatest fortifications could be taken by surprise. Edward's response was typically systematic: he rebuilt and strengthened, including beginning the magnificent Beaumaris Castle on Anglesey as the final link in his defensive chain.

The most serious challenge came over a century later, when Owain Glyndŵr launched his revolt for Welsh independence in 1400. Glyndŵr captured Conwy, Harlech, and Aberystwyth castles, holding Harlech as his headquarters and effective capital for several years. The eventual recapture of these fortresses by Henry IV and his son ended the revolt, but the episode demonstrated that Welsh resistance had not been permanently extinguished.

The Later Medieval Period and Decline

After the suppression of Glyndŵr's revolt, the great Welsh castles gradually declined in military significance. The Wars of the Roses (1455–1485) saw some of them, notably Harlech, used as Lancastrian strongholds, but by the Tudor period most had ceased to serve active military functions.

The Tudor dynasty, with its Welsh roots, brought a change in the symbolic meaning of Welsh castles. Henry VII's descent from the Welsh princes was carefully emphasised in Tudor propaganda, transforming the castles from instruments of conquest into monuments of a shared heritage. This was a remarkable act of historical rebranding.

Civil War and Destruction

The English Civil War of the 1640s brought the Welsh castles back into active military use, many serving as Royalist strongholds. Conwy, Raglan, and Pembroke were all besieged by Parliamentary forces. The aftermath saw deliberate slighting: the systematic demolition of fortifications to prevent future military use. Many Welsh castles bear the marks of this seventeenth-century destruction, their walls breached or towers blown apart with gunpowder.

Romantic Revival and World Heritage

The eighteenth and nineteenth centuries saw the ruins of Welsh castles reinterpreted through the lens of the Romantic movement. What had been seen as obsolete military structures became sublime monuments to the medieval past. Painters like Richard Wilson and J.M.W. Turner depicted Welsh castles as picturesque ruins, while writers celebrated them as evocations of a heroic age.

Today, four of Edward I's castles in north Wales, Conwy, Caernarfon, Harlech, and Beaumaris, together with the walled town of Conwy, are designated as a UNESCO World Heritage Site, recognised as an outstanding example of medieval military architecture. They draw hundreds of thousands of visitors annually and remain among the most visited historic monuments in Britain.

A Landscape of Memory

The castles of Wales are not merely tourist attractions. They are the physical record of eight centuries of conflict, conquest, and cultural survival. Each one encodes a particular moment in the long struggle between Welsh and English, native and invader, resistance and accommodation.

To walk the walls of Caernarfon or climb the tower of Dolwyddelan is to encounter that history directly. The stone has not forgotten what happened here. Neither, in the deepest sense, has Wales.

For more detail on one of the most remarkable individual castles in this story, our article on Rhuddlan Castle explores how Edward I diverted an entire river to build his fortress and then used it as the seat of power from which he imposed English law on Wales.

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