In a series of battles fought all across Northumbria, Oswiu kept being pushed back until he reached the far north of his kingdom. When Osiwu wanted peace, Penda took Oswiu's son Ecgfrith as a hostage. Oswiu also made an offer of tribute to Penda if he would bring an end to the hostilities. According to Nennius, Oswiu gave Penda all the treasure he had which Penda gave to his Briton allies. But Bede claims Penda turned down the offer of treasure as tribute. Penda took his army and left Bernicia. It was at this point, according to Bede, that Oswiu with a much smaller force attacked Penda's army. He caught up with Penda on the banks of the flooded Winwaed river. Some of Penda's allies deserted him and decided not to fight. But probably catching Penda's main force by surprise Oswiu's army fell upon the Mercians without mercy. Penda and most of the leaders of his 'thirty legions' were killed. Also killed with Penda was king Aethelhere of East Anglia. One of those who also withdrew and did not engage in the battle was Oswiu's nephew, King Athelwald of Deira. He had guided Penda through Northumbria and been his ally against his uncle. Because of the flooded river, more were killed by drowning than in battle.