Oswiu (c. 612–February 15, 670), also written as Oswio, Oswy, Oswig and Osuiu was King of Bernicia from 642 until his death and effectively ruled all Northumbria beginning in 655. He is the last king whom Bede states held imperium, and in the late 9th-century Anglo-Saxon Chronicle he is referred to as a Bretwalda.

Early reign

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Oswiu was the son of Æthelfrith and brother of Oswald, whom he succeeded in Bernicia in 642 after the Battle of Maserfeld, in which Oswald was killed; however, Oswine, a relative of Edwin, became king of Deira, the other of the two kingdoms that constituted Northumbria, at some point in the years following the battle. Maserfield and its consequences clearly left Oswiu in an initially weaker position than his brother; while Oswald had been the most powerful ruler in Britain, Oswiu faced the dominance of Penda of Mercia, who had defeated Oswald, during the early part of his reign. Bede mentions that Oswiu recovered Oswald's remains (he had been dismembered after his death in battle) in the year after Maserfield.

Oswiu succeeded in subjugating many of the Britons, Picts and Scots. At Gilling in 651, he plotted the murder of Oswine and a few years later took possession of Deira, thus once more reuniting Bernicia and Deira into the kingdom of Northumbria. From then onward Deira would be only a subkingdom of Northumbria.

Oswiu appears to have consolidated his power by the aid of the Roman Church and by a series of judicious matrimonial alliances. It was probably in 642 that he married Eanfled, daughter of Edwin, thus uniting the two rival dynasties of Northumbria. His daughter Alchflaed he married to Peada, son of Penda, the king of Mercia; another daughter, Osthryth, became the wife of Æthelred, Penda's third son. Oswiu was chiefly responsible for the reconversion of the East Saxons. He is said to have convinced their king, Sigeberht II, of the truth of Christianity by his arguments, and at his request sent Cedd, a brother of Chad of Mercia (St. Chad), on a mission to Essex.

Overlord of Britain

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In the years after Maserfield, Oswiu continued to face hostility from Penda, whose attacks on Bernicia are mentioned by Bede; on one occasion, he unsuccessfully besieged the royal city of Bamburgh. In 655, Penda led a large army composed of "thirty legions" (including the kings of East Anglia and Gwynedd) against Bernicia; Penda was also supported in his invasion by Aethelwald of Deira, the son of Oswald who had become king of Deira after Oswine's murder in 651. Oswiu was apparently driven to the north of his kingdom and besieged at a place called Iudeu, which is generally identified with Stirling; he offered Penda a large amount of treasure, although the sources contradict as to whether Penda accepted it. Apparently he also had to hand over his son Ecgfrith as a hostage. The events that followed are unclear, but led to a decisive battle on November 15 in which Oswiu defeated and killed the Mercian king at the Battle of the Winwaed.

The Battle of the Winwaed definitively changed the balance of power in Britain. Mercian power was crushed, and Mercia itself was divided into two parts: the southern part was given to Penda's son Peada, who had married Oswiu's daughter, while Oswiu himself took control of the northern part. Oswiu was from this point clearly the most powerful ruler in Britain. As a thanksgiving offering he dedicated his daughter Rifled to the Church, and founded the monastery of Whitby. About this time he is thought by many to have obtained some footing in the kingdom of the Picts through their king Talorcan, the son of his brother Eanfrith.

At the death of Peada in 656 Oswiu took control of the whole of Mercia himself, but was overthrown in 658 by a revolt under the leadership of Wulfhere of Mercia, a younger brother of Peada. Still he remained the most powerful and influential king in Britain at the time.

In 660 Oswiu married his son Ecgfrith to Æthelthryth, daughter of the former East Anglian king Anna. In 664 at the synod of Whitby, Oswiu accepted the usages of the Roman Church, which led to the departure of Saint Colman and the appointment of Wilfrid as bishop of York. Oswiu died in 670 and was succeeded by Ecgfrith.

610s births | 670 deaths | Anglo-Saxon monarchs | Mercian monarchs

Oswiu | Oswiu de Northumbria | Oswiu di Northumbria | Oswiu av Northumbria