On the death of Griffith ap Llywelyn, many princes tried to become supreme. Bleddyn of Powys, a good and merciful prince, became the most important.

In January 1070, when the snow lay thick on the mountains, William, the Norman Conqueror, appeared at Chester with an army. He had defeated and killed Harold, the conqueror of Griffith ap Llywelyn, in 1066; he had crushed the power of the Mercian allies of Bleddyn; he had struck terror into the wild north, and England lay at his feet.

He turned back from Chester, but he placed on the borders a number of barons who were to conquer Wales, as he had conquered England. They had a measure of his ability, of his energy, and of his ambition.

The two great Norman traits were wisdom and courage; but the one was often mere cunning, and the other brutal ferocity. But no one like the Norman had yet appeared in Wales - no one with a vision so clear, or with so hard a grip. A hard, worldly, tenacious, calculating race they were; and they turned their faces resolutely towards Wales.

From England, Wales can be entered and attacked along three valleys - along the Dee, the Severn, and the Wye. At Chester, Hugh of Avranches, called "The Wolf," placed himself. From its walls he could look over and covet the Welsh hills, as he could have looked over the Breton hills from Avranches. He loved war and the chase: he despised industry, he cared not for religion; he was a man of strong passions, but he was generous, and he respected worth of character. One of his followers, Robert, had all his vices and few of his virtues. It was he who extended the dominions of the Earl of Chester along the north coast to the Clwyd, where he built a castle at Rhuddlan; and thence on to the valley of the Conway, where he built a castle at Deganwy. The cruelty of Robert shocked even the Normans of his time. He even set foot in Anglesey, which looked temptingly near from Deganwy, and built a castle at Aberlleiniog.

At Shrewsbury, where the Severn, after leaving the mountains of Wales, turns to the south, Roger of Montgomery was placed, with his wife Mabel, an energetic little woman, hated and feared by all. Roger himself, while ever ready to fight, preferred to get what he wanted by persuasion; he was not less cruel than Hugh of Chester, but he was less fond of war. He and his sons pushed their way up the Severn, and built a castle at Montgomery.

To Hereford, on the Wye, William Fitz-Osbern came. He was the ablest, perhaps, of all the followers of the Conqueror. He entered Wales; he saw it from the Wye to the sea, and he thought it was not large enough, and that it was too far from the political life of the time. So he went back to Normandy, but he left his sons William and Roger behind him. William had his father's wisdom. Roger had his father's recklessness in action; he rebelled against his own king, and found himself in prison. The king sent him, on the day of Christ's Passion, a robe of silk and rarest ermine. The caged baron made a roaring fire, and cast the robe into it. "By the light of God," said William the Conqueror, for that was his wicked oath, "he shall never leave his prison."

But another Norman, Bernard of Neufmarche, came to take his place. He built his castle at Brecon, and defeated and killed Rees, the King of Deheubarth; and, with great energy, he took possession of the upper valleys of the Wye and the Usk.

Further south William the Conqueror himself came to Cardiff, and possibly built a castle. The Norman conquest of the south coast of Wales was exceedingly rapid, and castle after castle rose to mark the new victorious advances - Coety, Cenfig, Neath, Kidwelly, Pembroke, Newport, Cilgeran.

So far, the Norman advance has been a most quick one. In less than twenty-five years from the appearance of the Conqueror at Chester, the whole country had been overrun except the mountains of Gwynedd and the forests of the Deheubarth. This success is easily explained.

For one thing, the Normans had trained, professional soldiers, who were well horsed and well armed. In a pitched battle the hastily collected Welsh levies, unused to regular battle and very lightly armed, had no chance.

Again, the Norman never receded. He was willing to stop occasionally, in order to bide his time; but he clung tenaciously to every mile he had won. His skill as a castle builder was as striking as his prowess in battle or his cautious wisdom in council. He took possession of an old fortified post, or hastily constructed one of turf and timber; but he soon turned it into a castle of stone. At that time the Welsh had no knowledge of sieges; and their impetuous valour was of no use against the new castles.

Again, the Welsh opposition was not only not organised, but weakened by internal strife. While the Norman was winning valley after valley, the Welsh princes were trying to decide by the issue of battle who was to be chief. Bleddyn was slain in 1075; and his nephews and cousins tried to rule the country. Among these, Trahaiarn was a soldier of ability and energy, and a ruler of real genius. But he was the rival of the exiled princes of the House of Cunedda, and he found it difficult to bend Snowdon and the Vale of Towy to his will. Two of the exiles met him, probably near some of the cairns in the valley of the Teivy; and there, in the battle of Mynydd Carn, fiercely fought through the dusk into a moonlight night in 1079, Trahaiarn fell. It looked as if no leader could rise in Wales to fight a Norman army or to take a Norman castle.