Seven Kingdoms are traditionally identified as being established by these Saxon migrants.

Three are clustered in the South east: Sussex, Kent and Essex.

The Midlands are dominated by the kingdoms of Mercia and East Anglia.

The lineage of the monarchs of Mercia is determined to reach as far back as the early 500's.

To the north is Northumbria, which unifies two earlier kingdoms, Bernicia and Deira.

The development of these kingdoms will lead to the eventual domination by Northumbria and Mercia in the seventh century, Mercia in the eighth century, then Wessex in the ninth century.

Northumbria extends its control north into Scotland and west into Wales.

It also subdues Mercia, whose first powerful King, Penda, is killed by Oswy in 655.

The Deiran exile Hereric had been poisoned while at the court of Ceretic, king of Elmet; Æthelfrith may have been responsible for this killing.

Edwin, apparently seeking safety from Æthelfrith, seems to have traveled between many different kingdoms during his period of exile.

He may have spent time during his exile in the British kingdom of Gwynedd, and it seems clear that he spent time in Mercia, because he married a daughter of king Cearl.

Edwin ended up in East Anglia, under the protection of its king, Raedwald.

Æthelfrith had sent messengers to bribe Raedwald with "a great sum of money" into killing Edwin; Bede reports that his first message had no effect, but Æthelfrith had sent more messengers and threatened war if Raedwald did not comply (bribes and threats of this kind may have previously been used to accomplish Hereric's killing.)

Raedwald had eventually agreed to kill Edwin or hand him over to Æthelfrith's messengers, but was reportedly dissuaded from this by his wife, who said that such a thing was unworthy of his honor.

Instead, Raedwald raises an army and marches against Æthelfrith, and around 616 Æthelfrith is defeated and killed on the east side of the River Idle by an army under Raedwald; Bede says that Æthelfrith had the inferior army, because Raedwald had not given him time to bring all his forces together.

While presented by Bede as being fought simply over the issue of Edwin, this war may have actually involved questions of power and territory between the two rulers.

Æthelfrith's heir, prince Eanfrith, seeks refuge with his mother's family, probably in Gododdin (modern Scotland) and moves further north into Pictland.

Æthelfrith's younger sons Oswald and Oswiu escape to the court of king Eochaid Buide of Dál Riata, where they are soon converted to Christianity by the monks of Iona.

King Oswald and his Northumbrian army besiege and conquer Edinburgh.

His half-brother, Oswiu of Bernicia, marries princess Rhiainfelt, heiress of North Rheged ("Old North").

Northumbria embraces North Rheged in a peaceful takeover and Oswiu becomes a sub-king.

Oswald devotes his energies to securing the borders of his united Northumbrian kingdom and extending his authority southward.

Prince Oswiu of Bernicia conquers Gododdin or "The Old North" as far north as Manaw Gododdin, the narrow coastal region on the south side of the Firth of Forth, on behalf of his half-brother, king Oswald.

King Penda of Mercia, now a competitor to Oswald of Northumbria, defeats and kills the latter on August 5, 642, in the battle of Maserfield.

He commands a united British and Mercian force which includes the Welsh army of kings Cadafael Cadomedd of Gwynedd and Cynddylan of Pengwern.

The cause of the war that led to Maserfield is unknown.

The Mercians after the battle become dominant in the English Midlands.

Deira, in the southern part of Northumbria, chooses a king of its own, Oswine, while Bernicia in the north (which had been dominant, with Oswald, a member of the Bernician royal line, ruling both Bernicia and Deira prior to Maserfield) is ruled by Oswald's brother Oswiu.

The battle thus leads to the internal weakening and fracturing of the Northumbrian kingdom, a situation which will last until after the battle of the Winwaed, despite Oswine's murder in 651 on the orders of Oswiu.

Oswiu, King of Bernicia, head of the rival Northumbrian royal family, in 642 sends a priest named Utta to Kent, which is at this time ruled by Eanflæd's cousin, Eorcenberht, to ask for her hand in marriage.

Oswiu already had been married, to a British princess, named Rieinmellt, but as King Penda of Mercia, the victor of Maserfield, dominates central Britain, Oswiu is in need of support.

Marriage with Eanflæd would provide Kentish, and perhaps Frankish, support, and any children Oswiu and Eanflæd might have would have strong claims to all of Northumbria.

The date of the marriage is not recorded.

Oswiu's goal in marrying Eanflæd may have been the peaceful acceptance of his rule in Deira, but the plan is unsuccessful.

His paternal cousin Oswine, son of the late king Osric of Deira, manages by 644 to establish himself as king of Deira despite armed objections from Oswiu.

His succession, probably the choice of the people of Deira, splits the informally unified kingdom of Northumbria.

Oswiu, after seven years of peaceful rule, declares war on Oswine, who refuses to engage in battle, instead retreating to …

…Gilling, where he is betrayed by a friend, and murdered by Oswiu’s soldiers.

Oswine is buried at Tynemouth, but will later be forgotten.

Œthelwald succeeds his uncle Oswine as king of Deira and allies himself with Oswiu's enemy, king Penda of Mercia.

Queen Eanflæd of Bernicia donates the estate of Gilling for the foundation of a monastery.

Penda invades Bernicia and besiege Oswiu at Bamburgh.