The science and Biblical knowledge which fled from the Continent took refuge in famous schools which made Durrow and Armagh the universities of the West. The new Christian life soon beat too strongly to brook confinement within the bounds of Ireland itself. Patrick, the first missionary of the island, had not been half a century dead when Irish Christianity flung itself with a fiery zeal into battle with the mass of heathenism which was rolling in upon the Christian world. Irish missionaries laboured among the Picts of the Highlands and among the Frisians of the northern seas. An Irish missionary, Columban, founded monasteries in Burgundy and the Apennines. The canton of St. Gall still commemorates in its name another Irish missionary before whom the spirits of flood and fell fled wailing over the waters of the Lake of Constance. For a time it seemed as if the course of the world's history was to be changed, as if the older Celtic race that Roman and German had swept before them had turned to the moral conquest of their conquerors, as if Celtic and not Latin Christianity was to mould the destinies of the Churches of the West.
On a low island of barren gneiss-rock off the west coast of Scotland an Irish refugee, Columba, had raised the famous monastery of lona. Oswald in youth found refuge within its walls, and on his accession to the throne of Northumbria he called for missionaries from among its monks. The first despatched in answer to his call obtained little success. He declared on his return that among a people so stubborn and barbarous success was impossible. "Was it their stubbornness or your severity?" asked Aidan, a brother sitting by; "did you forget God's word to give them the milk first and then the meat?" All eyes turned on the speaker as fittest to undertake the abandoned mission, and Aidan sailing at their bidding fixed his bishop's stool or see in the island-peninsula of Lindisfarne. Thence, from a monastery which gave to the spot its after name of Holy Island, preachers poured forth over the heathen realms. Boisil guided a little troop of missionaries to the valley of the Tweed. Aidan himself wandered on foot preaching among the peasants of Bernicia. The new religion served as a prelude to the Northumbrian advance.
If Oswald was a saint, he was none the less resolved to build up again the realm of Eadwine. Having extended his supremacy over the Britons of Strath-clyde and won the submission of the Lindiswaras, he turned to reassert his supremacy over Wessex. The reception of the new faith became the mark of submission to his overlordship. A preacher, Birinus, had already penetrated from Gaul into Wessex; in Oswald's presence its king received baptism, and established with his assent a see for his people in the royal city of Dorchester on the Thames. Oswald ruled as wide a realm as his predecessor; but for after times the memory of his greatness was lost in the legends of his piety. A new conception of kingship began to blend itself with that of the warlike glory of aethel-frith or the wise administration of Eadwine. The moral power which was to reach its height in aefred first dawns in the story of Oswald. In his own court the king acted as interpreter to the Irish missionaries in their efforts to convert his thegns. "By reason of his constant habit of praying or giving thanks to the Lord he was wont wherever he sat to hold his hands upturned on his knees." As he feasted with Bishop Aidan by his side, the thegn, or noble of his war-band, whom he had set to give alms to the poor at his gate, told him of a multitude that still waited fasting without.
The king at once bade the untasted meat before him be carried to the poor and his silver dish be divided piecemeal among them. Aidan seized the royal hand and blessed it. "May this hand," he cried, "never grow old".
Prisoned, however, as it was by the conversion of Wessex to the central districts of England, heathendom fought desperately for life. Penda was still its rallying-point; but if his long reign was one continuous battle with the new religion, it was in fact rather a struggle against the supremacy of Northumbria than against the supremacy of the Cross. East Anglia became at last the field of contest between the two powers. In 642 Oswald marched to deliver it from Penda; but in a battle called the battle of the Maserfeld he was overthrown and slain. His body was mutilated and his limbs set on stakes by the brutal conqueror; but legend told that when all else of Oswald had perished, the "white hand" that Aidan had blessed still remained white and un-corrupted. For a few years after his victory at the Maserfeld Penda stood supreme in Britain. Wessex owned his overlordship as it had owned that of Oswald, and its king threw off the Christian faith and married Penda's sister. Even Deira seems to have bowed to him, and Bernicia alone refused to yield.
Year by year Penda carried his ravages over the north; once he reached even the royal city, the impregnable rock-fortress of Bamborough. Despairing of success in an assault, he pulled down the cottages around, and, piling their wood against its walls, fired the mass in a fair wind that drove the flames on the town. " See, Lord, what ill Penda is doing," cried Aidan from his hermit cell in the islet of Fame, as he saw the smoke drifting over the city; and a change of wind - so ran the legend of Northumbrian agony - drove back at the words the flames on those who kindled them. But in spite of Penda's victories, the faith which he had so often struck down revived everywhere around him. Burnt and harried as it was, Bernicia still clung to the Cross. The East-Saxons again became Christian. Penda's own son, whom he had set over the Middle-English, received baptism and teachers from Lindisfarne. The missionaries of the new faith appeared fearlessly among the Mercians themselves, and Penda gave no hindrance.
Heathen to the last, he stood by unheeding if any were willing to hear; hating and scorning with a certain grand sincerity of nature " those whom he saw not doing the works of the faith they had received." But the track of Northumbrian missionaries along the eastern coast marked the growth of Northumbrian overlordship, and the old man roused himself for a last stroke at his foes. On the death of Oswald Oswiu had been called to fill his throne, and in 655 he met the pagan host near the river Winwaed. It was in vain that the Northumbrians had sought to avert Penda's attack by offers of ornaments and costly gifts. " Since the pagans will not take our gifts," Oswiu cried at last, "let us offer them to One that will;" and he vowed that if successful he would dedicate his daughter to God and endow twelve monasteries in his realm. Victory at last declared for the faith of Christ. The river over which the Mercians fled was swollen with a great rain; it swept away the fragments of the heathen host, Penda himself was slain, and the cause of the older gods was lost for ever.