The **Battle of the Winwaed** (Welsh: *Cai*) was fought on 15 November 655 between the forces of Kings Penda of Mercia and Oswiu of Bernicia. The outcome of the battle was a major victory for Oswiu and a restoration of Northumbrian dominance of Anglo-Saxon England.

Background
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Several events led to the battle of the Winwaed. King Oswald of Northumbria was considered the bretwalda or overlord over the other Anglo-Saxon kingdoms in England. Penda of Mercia defeated and killed Oswald of Northumbria in 642 at the battle of Maserfield. This left Penda the most powerful king in England. Penda did not claim to be the overlord, however. When his brother Oswald was killed, Oswiu of Northumbria claimed the throne of Bernicia but was not able to rule Deira. It was a year before Oswiu felt it was safe enough to recover his brother's body from the battlefield where he was killed. To appease Penda Oswiu gave his daughter in marriage to Penda's son Peada. Also Oswiu agreed to the marriage of his son Alfrith and Penda's daughter Cyneburh. Still, Penda was not satisfied. He was determined to destroy Oswiu. In 654 Penda raised a large army of some thirty 'legions'. Then, about 653, Penda began raiding into Bernicia.

The battle
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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.

Effects
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The death of Penda and the rise of Oswiu to dominance had a major impact in 7th century England. Athelwald was either killed or went into exile. From this time Oswiu became the bretwalda or overlord over all the southern English people including Mercia. Mercia was then divided. North of the River Trent was controlled directly by Oswiu. He made Peada of Mercia, Penda's son, king over the part of Mercia south of the Trent. Peada had married Oswiu's daughter, Alflaed. Peada was murdered five months later by Alflaed, possibly on Oswiu's orders. Mercians rebelled against Oswiu and Peada's brother Wulfhere became king of Mercia.

Other websites
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* Kings of Northumbria[*permanent dead link*]
* Anglo-Saxon West Yorkshire: The Historical Background Archived 2011-07-28 at the Wayback Machine