The Battle of [the] Winwæd in 655 is a little known and sparsely recorded battle, yet one of critical importance to the social, political and religious evolution of the various Anglo-Saxon kingdoms from the seventh century. While the death of the pagan king of Mercia, Penda, and significant numbers of his allies was not enough to permanently arrest Mercian political ascendency, it is often considered to be the catalyst for the decline of Anglo-Saxon paganism. According to the Anglo-Saxon Chronicle:
In this year  Penda perished and the Mercians became Christians. (Anglo-Saxon Chronicle, C-Text).
In this year  Oswiu killed Penda at Winwædfeld and 30 princes with him, and some of them were kings. One of them was Æthelhere, brother of Anna, king of the East Angles. (Anglo-Saxon Chronicle, E-Text).