Oswald was the son of Æthelfrith of Bernicia. After spending a period in exile on Iona where he was trained and educated by Irish monks, he returned to Northumberland and defeated the British ruler Cadwallon, Oswald brought the two Northumbrian kingdoms of Bernicia and Deira once again under a single ruler, and promoted the spread of Christianity in Northumbria. He was given a strongly positive assessment by the historian Bede, writing a little less than a century after Oswald's death, who regarded Oswald as a saintly king;
it is also Bede who is the main source for present-day historical knowledge of Oswald. After eight years of rule, in which he was the most powerful ruler in Britain,
Before the battle, Oswald had a wooden cross erected. He knelt down and held the cross in position until enough earth had been thrown in the hole to make it stand firm. He then prayed and asked his army to join in. Oswald is said to have had a vision of Columba on the the night before the battle, in which the victory was foretold.