Northumbria, a kingdom of Angles, in what is now northern England and south-east Scotland, was initially divided into two kingdoms: Bernicia and Deira. The two were first united by Aethelfrith around the year 604, and except for occasional periods of division over the subsequent century, they remained so. The exceptions are during the brief period from 633 to 634, when Northumbria was plunged into chaos by the death of King Edwin in battle and the ruinous invasion of Cadwallon ap Cadfan of Gwynedd. The unity of the Northumbrian kingdoms was restored after Cadwallon's death in battle in 634.