Penda of Mercia
After King Oswald's death, Northumbria divided back into the two previous kingdoms of Bernicia and Deira. Each had their own king. Oswiu of Northumbria became king of Bernicia. He was Oswald's brother and Penda had a particular contempt for him. In 653 Deira came under Mercian control. In 654, hoping to put an end to Oswiu, Penda gathered all his allies and invaded Bernicia. Called the battle of the Winwaed he marched against Oswiu with 'thirty legions'. On Sunday, 15 November 655 the two armies met in battle near Leeds. Although he had the larger army Penda was killed. This established Oswiu as king of all Northumbria and as overlord of all the English south of the River Humber. Penda was succeeded by his son Peada.