With the help of the travelling Bishop Germanus' and the legendary Cunedda (Kenneth) of Wales, the British were able to contain the threat of Irish settlement and Invasio
By the time that Vortigern had come to power in Britain around the year AD 427, the Irish had already established a number of settlements in Wales, most notably in the north. These settlements were being used as advance bases by Irish, Pict, and Saxon raiders to launch strikes deeper into Britain. The situation became desperate for the British in AD 429 when a large army of Saxons and Picts aided by the Irish settlements struck out through Wales.
In that same year, the Bishop Germanus of Auxerre was sent to Britain by the Bishops of Gaul in order to combat the growing Pelagian* heresy that had taken root in Britain. Arriving on the Island, Germanus immediately saw that the physical threat of barbarian invasion was a more immediate problem than the heresy. Having once been a soldier, Germanus offered his services to Vortigern to help counter the Barbarian threat. The desperate Vortigern gave Germanus command of the small army that could be assembled. Germanus took this force into Wales. After locating the enemy, Germanus positioned his men in a narrow valley ahead of the enemy advance (This valley may have been the one containing the present town of Llangollen). As the Saxons and Picts came down the valley, Germanus ordered his men to shout “Alleluia” as one. This they did again and again. Their great shout echoed off the valley walls. The terrifying noise broke the enemy ranks, and the Saxons and the Picts fled in all directions.
Although Germanus’ bloodless victory had countered the immediate threat, the problem of the Irish settlements remained. To answer this problem, Vortigern made two moves. His first was to arrange the marriage of his daughter to the Irish King as part of a treaty to stop Irish settlement in Britain. His second move was to set loose the tribal leader Cunedda (of Cumbria) in Wales. Cunedda (now called Kenneth) was the grandson of Paternus, one of the Romans installed as leaders over the Celtic tribes by Count Theodosius some fifty years before. Little is known of Cunedda’s campaigns in Wales except that the outcome was the complete subjugation of the Irish settlements.
With the battle of Germanus and the campaign of Cunedda along with the political manoeuvring by Vortigern, the Irish threat had been ended. Vortigern had very little time to enjoy his victories however, for a new internal threat was mounting against him.
*Pelagius denied the teaching of original sin. He preached that man was essentially good and controlled his own destiny to reach the afterlife which could be earned through good works. His teachings implied that neither God, nor the sacrifice of Jesus, was necessary for eternal life.