The armies met in 633 at a place called the Heathfield, and in the fight which followed Eadwine was defeated and slain.
[Sidenote: Oswald] Bernicia seized on the fall of Eadwine to recall the line of AEthelfrith to its throne; and after a year of anarchy his second son, Oswald, became its king.

The Welsh had remained encamped in the heart of the north, and Oswald's first fight was with Cadwallon.

A small Northumbrian force gathered in 635 near the Roman Wall, and pledged itself at the new King's bidding to become Christian if it conquered in the fight.

Cadwallon fell fighting on the "Heaven's Field," as after times called the field of battle; the submission of Deira to the conqueror restored the kingdom of Northumbria; and for seven years the power of Oswald equalled that of Eadwine.

It was not the Church of Paulinus which nerved Oswald to this struggle for the Cross, or which carried out in Bernicia the work of conversion which his victory began.