The Battle of Chester (in Old Welsh, Guaith Caer Legion and in modern Welsh, Brwydr Caer), is generally agreed to have taken place in 616, as first argued by Charles Plummer, although near contemporary annals give a variety of dates. It was fought between the Northumbrians of King Æthelfrith and a number of Northern Welsh kingdoms, certainly including Powys and Rhôs. Northumbria was victorious and Kings Selyf Sarffgadau of Powys and Cadwal Crysban of Rhôs were both killed in the slaughter. Circumstantial evidence suggests that King Iago of Gwynedd may also have been amongst the dead.

Bede records that a large number of monks from Bangor-on-Dee "resorted...to pray at the...battle...King Ethelfrid being informed [of this]...said, "If then they cry to their God against us, in truth, though they do not bear arms, yet they fight against us, because they oppose us by their prayers." He, therefore, commanded them to be attacked first ... About twelve hundred of those that came to pray are said to have been killed". Bede thought this was divine retribution for the Welsh bishops having refused to submit to St. Augustine.

The Anglo-Saxon Chronicle says, for year 605 in one version and year 606 in another version:-

And her Æðelfrið lædde his færde to Legercyestre, 7 ðar ofsloh unrim Walena. 7 swa wearþ gefyld Augustinus witegunge. þe he cwæþ. Gif Wealas nellað sibbe wið us. hi sculan æt Seaxana handa farwurþan. Þar man sloh eac .cc. preosta ða comon ðyder þæt hi scoldon gebiddan for Walena here. Scrocmail was gehaten heora ealdormann. se atbærst ðanon fiftiga sum.

And here Æðelfrið led his army to Chester, and there slew countless Welsh. And came about Augustinus's prophesy, that he said "If they do not have peace with us, they will die at the hands of the Saxons.". There also were slain 200 priests who came there to pray for the Welsh army. Scrocmail was called their leader, and he escaped as one of fifty."

In the 'Cleopatra' version of the Welsh Brut y Brenhinedd, this conflict is called the Battle of Perllan Fangor (Bangor Orchard), perhaps indicating that it took place nearer Bangor than Chester. However, archaeological excavations at Heronbridge, just south of Chester, have discovered post-Roman graves buried beneath a defensive earthwork over an old Roman settlement. They may possibly be the bodies of Northumbrian casualties lying beneath a fortress built by their fellows subsequent to the Anglian victory.

The reasons behind the battle are unclear. Welsh tradition, chiefly expounded by the unreliable Geoffrey of Monmouth says that King Æthelfrith's political rival, Edwin of Deira was living in exile in Gwynedd around this time. Oblique references in the writings of Reginald of Durham and the Welsh Triads may indicate that this was indeed the case. However, there is no evidence that Æthelfrith was in pursuit of this man, as historians such as John Morris suggest. It has also been claimed that this battle finally severed the land connection between Wales and the old northern Brythonic kingdoms of Rheged and Alt Clut where the Cumbric language was spoken. However, whether this was by design or simply an accidental consequence is undetermined.

Some historians believe that King Arthur's "ninth battle...in the City of the Legion", as recorded by Nennius, is a misplaced reference to this later battle.

Skull from the Battle of Chester

References

• Anonymous (c.10th century). Annales Cambriae http://www.fordham.edu/halsall/source/annalescambriae.html
• Bede. Historia ecclesiastica gentis Anglorum, Book II, Chapter II http://www.fordham.edu/halsall/basis/bede-book2.html
• hua Braeinm, Tigernach (attribution) (c.10th century). Annals of Tigernach http://www.ucc.ie/celt/online/G100002/
• Bromwich, Rachel (ed.) (1978). Trioedd Ynys Prydein: The Welsh Triads. University of Wales Press.
• Durham, Reginald of (c.1150) Life of St. Oswald
• Marsden, John (1992). Northanhymbre Saga. Kyle Cathie.
• Mason, David (2004). Heronbridge excavation and research project. Chester Archaeological Society.
• Monmouth, Geoffrey of (1136). The History of the Kings of Britain.

• Parry, JJ (ed.) (1937). Brut y Brehinedd: Cotton Cleopatra Version Cambridge.
• Plummer, Charles (1896). Venerabilis Beda Opera Historica. Oxford.
• Snyder, Christopher A (2003). The Britons. Blackwell Publishing.

cy:Brwydr Caer fi:Chesterin taistelu