East-Anglia became at last the field of contest between the two powers; and in 642 Oswald marched to deliver it from the Mercian rule.
But his doom was the doom of Eadwine, and in a battle called the battle of the Maserfeld he was overthrown and slain.

For a few years after his victory at the Maserfeld, Penda stood supreme in Britain.

Heathenism triumphed with him.

If Wessex did not own his overlordship as it had owned that of Oswald, its king threw off the Christian faith which he had embraced but a few years back at the preaching of Birinus.

Even Deira seems to have owned Penda's sway.