David II., a mild and well-meaning prince, was too weak to carry his father's policy out. He tried to maintain peace, and did homage to his uncle, the King of England. But, as the head of the patriotic party, his more energetic brother, Griffith, opposed him. By guile he caught Griffith, and shut him in a castle on the rock of Criccieth. The other princes shook off the yoke of Gwynedd, and Henry III. tried to play the brothers against each other. David sent Griffith to Henry, who put him in the Tower of London. In trying to escape, his rope broke, and he fell to the ground dead. Soon afterwards, in 1246, in the middle of a war with Henry, David died of a broken heart.

The sons of Griffith - Owen, Llywelyn, and David - at once took their uncle's place; and by 1255 Llywelyn ap Griffith was sole ruler. By that year Henry III. had given his young son Edward the earldom of Chester, which had fallen to the crown, and the lands between the Dee and the Conway, which he claimed by a treaty with the dead Griffith. Thus Edward and Llywelyn began their long struggle.

Between 1255 and 1267 Llywelyn tries to recover his grandfather's position in Wales. In 1255 his power extended over Gwynedd only. He found it easy to extend it over most of Wales, because the rule of the English officials made the Welsh chiefs long for the protection of Gwynedd. The Barons' War paralysed the power of the King, and Llywelyn made an alliance with Simon de Montfort and the barons. Even after Montfort's fall in 1265 the barons were so powerful that the King was still at their mercy. In 1267 Llywelyn's position as Prince of Wales was recognised in the Treaty of Montgomery. His sway extended from Snowdon to the Dee on the east, and to the Teivy and the Beacons on the south - practically the whole of modern Wales, except the southern seaboard. Within these wide bounds all the Welsh barons were to swear fealty to Llywelyn, the only exception being Meredith ap Rees of Deheubarth.

The second struggle of Llywelyn's reign took place between 1267 and 1277. He tried to weld his land into a closer union, and many of the chiefs of the south and east became willing to call in the English King. Two of them, his own brother David and Griffith of Powys, fled to England, and were received by Edward, who had been king since 1272. Llywelyn and Edward distrusted each other. Edward wished to unite Britain in a feudal unity, and to crush all opponents. Llywelyn thought of helping the barons; he might become their leader. Eleanor, the daughter of Simon de Montfort, the old leader of the barons, was betrothed to him. War broke out. The barons - Clares and Mortimers, and all - joined the King. Llywelyn's dominions were invaded at all points, his barons had to yield, one after the other; and finally, in 1277, Llywelyn had to accept the Treaty of Rhuddlan. His dominions shrunk to the old limits of Snowdon, his sway over the rest of Wales was taken from him, and the title of Prince of Wales was to cease with his life.

The third struggle was between 1277 and 1282. The rule of the new officials drove the Welsh to revolt; and the chiefs who had opposed Llywelyn, especially his brother David, begged for Llywelyn's protection. Eleanor, Llywelyn's wife and Edward's cousin, tried to keep the peace, but she died while they were arming for the last bitter war of 1282.

It was comparatively easy for Edward to overrun Powys or Deheubarth, if he had an army strong enough. But at that time Gwynedd was almost impregnable. From Conway to Harlech lies the vast mass of Snowdon, a great natural rampart running from sea to sea. Its steep side is towards the east, and the invader found before him heights which he could not climb, and round which he could not pass. If you stand in the Vale of Conway, look at the hills on the Arvon side - the great natural wall of inmost Gwynedd, with its last tower, the Penmaen Mawr, rising right from the sea. The gentle slopes are to the west, and there the corn and flocks were safe.

Edward had to put a large army into the field, and it cost him much. In the war with Llywelyn he had to change the English army entirely; and, in order to get money, he had to allow the Parliament to get life and power. To carry supplies, and to land men in Anglesey to turn the flank of the Welsh, he wanted a fleet. But there was no royal navy then, and the fishermen of the east coast and the south coast - who had no quarrel with the Welsh, but were very anxious to fight each other - were not willing to lose their fish harvest in order to fight so far away.

In 1282, Edward's great army closed round Snowdon. The chiefs still faithful to Llywelyn had to yield or flee. But winter was coming on, and could Edward keep his army in the field? An attempt had been made to enter Snowdon from Anglesey, but the English force was destroyed at Moel y Don. It looked as if Edward would have to retire. Llywelyn left Snowdon, and went to Ceredigion and the Vale of Towy to put new heart in his allies, and from there he passed on to the valley of the Wye. He meant, without a doubt, to get the barons of the border, Welsh and English, to unite against Edward. But in some chance skirmish a soldier slew him, not knowing who he was. When they heard that their Prince was fallen, his men in Snowdon entirely lost heart. They had no faith in David, and in a few months the whole of Wales was at Edward's feet.