We now come to the introduction of Christianity into Northumbria, which arose through the marriage of Æthelbert, King of Kent, at the close of the sixth century, with Bertha, daughter of King Charibert of Paris, who, being a convert to the Christian religion, made it a condition of her marriage that she should be allowed to worship in a small Roman-built church near Canterbury. Early in the next century Edwin, King of Northumbria, married Æthelburga, the daughter of Æthelbert, who, also being a Christian, took with her Paulinus, a follower of St. Augustine (see Chapter IX.). It was not so easy, however, to make a convert of her husband, but after some delay he called together his Council, who declared themselves in favour of the new religion, and many of them were baptized at York, A.D. 627. This conversion led to a war between Edwin and the King of Mercia, who still held to his faith in Woden and Thor, when the King of Northumbria was killed at the battle of Hatfield in 633. Shortly after this, Cædwallon, King of the Welsh, became ruler over Northumbria, but only for a short time, as he was defeated and slain in battle by Oswald, who, afterwards succeeding to the thrones of Bernicia and Deira, again united Northumbria, and re-established the Christian creed. But Penda was determined to maintain the pagan religion, and, defeating Oswald at the battle of Maserfeld in 642, again held Northumbria. Subsequently another division appears to have taken place, and Lancashire became part of the kingdom of Deira, its ruler being Oswine, and continued so for some six years, when Oswi, who reigned in Bernicia (the other portion of Northumbria), caused Oswine to be slain, and again united the two kingdoms. Alcfrid, the son of Oswi, having married Cyneburga, daughter of Penda, was about this time appointed Regent over Deira, and afterwards a further fusion of the two families was brought about by the marriage of Alcfrid's sister to Peada, son of Penda.