Battle of Chester The Battle of Chester ( Old Welsh : " Guaith Caer Legion " ; Welsh : " Brwydr Caer " ) was a major victory for the Anglo Saxons over the native Britons near the city of Chester , England in the early 7th century . Æthelfrith of Northumbria annihilated a combined force from the Welsh kingdoms of Powys , Rhôs ( a cantref of the Kingdom of Gwynedd ) and possibly Mercia . It resulted in the deaths of Welsh leaders Selyf Sarffgadau of Powys and Cadwal Crysban of Rhôs . Circumstantial evidence suggests that King Iago of Gwynedd may have also been killed . According to Bede , a large number of monks from the monastery at Bangor on Dee who had come to witness the fight were killed on the orders of Æthelfrith before the battle . He told his warriors to massacre the clerics because although they bore no arms , they were praying for a Northumbria defeat . The strategic significance of the battle remains unclear as Æthelfrith died in battle soon after the victory . It has been suggested that Cearl , the Anglo Saxon king of Mercia , may have also been involved and shared in the Britons ' defeat because his overkingship of eastern Wales and Mercia effectively ended until the rise of his successor , Penda by 633 . Historical sources . Battle . Historian Charles Plummer , best known as an editor of Bede , believed that the battle occurred around 615 or 616 . But near contemporary annals give a variety of dates . 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 . " < br > And here Æðelfrið led his army to Chester , and there slew countless Welsh . And came about Augustinus ' s prophecy , 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 " Brut y Brenhinedd " ( ) , which is a collection of variant Middle Welsh versions of Geoffrey of Monmouth ' s Latin chronicle " Historia Regum Britanniae " ( " History of the Kings of Britain " ) , the battle is called " Perllan Fangor " ( ) . " Brut " proved especially influential in medieval Wales , where it was largely regarded as an accurate account of the early history of the Britons . It therefore suggests the battle may have taken place nearer to Bangor - on - Dee rather than Chester . Some historians believe that King Arthur ' s " ninth battle . . . in the City of the Legion " ( " urbs legionis " ) , as recorded by Nennius , is a misplaced reference to this later battle . Massacre . Bede is the only contemporary author who mentions the killings of monks . He wrote that the monks : " resorted . . . to pray at the . . . battle . . . King Æthelfrith 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 refusing to join Augustine of Canterbury in proselytizing the Saxons . During the English Reformation scholars such as Matthew Parker frequently argued that Augustine himself had been complicit in the battle and the massacre , but this contention swiftly degenerated into a sectarian dispute . The argument relies on the 604 date for the battle found in the " Anglo - Saxon Chronicle " as well as the suggestion that a passage in Bede that specifically exculpates Augustine , which appears in the Latin but not in the early English translation of the text , was a later addition aimed at distancing the churchman from the violence he predicted . The usually accepted dates 615 / 16 for the battle mitigate this argument , as Augustine is believed to have died in 604 . The charge against Augustine was challenged or rejected by scholars of the 18th and 19th century such as Elizabeth Elstob , Henry Spelman , Henry Wharton , and Jeremy Collier . That Æthelfrith and his army were pagan is a further difficulty with the theory , which has no support from modern historians . Archaeology . Archaeological excavations at Heronbridge , just south of Chester , uncovered post - Roman graves buried beneath a defensive earthwork over an old Roman settlement . They may contain the bodies of Northumbrian casualties . Significance . The precise reasons for the battle are unknown but Geoffrey of Monmouth states that King Æthelfrith ' s political rival , Edwin of Deira , was living in exile in Gwynedd . Although Geoffrey of Monmouth is often regarded as an unreliable source , there are some supporting references to Edwin in the writings of Reginald of Durham and the Welsh Triads . However , there is no evidence that Æthelfrith was in pursuit of Edwin . The battle ' s outcome was once believed to have led to the severing of the land connection between Wales and the Old North - the old northern Brython ic kingdoms of Rheged and Kingdom of Strathclyde . The Battle of Deorham is held to have separated the Welsh peninsula from the West Country ( all these kingdoms covered land where Brythonic language s were spoken ) . However this view is now " generally understood " to be outdated as there is " almost no archaeological evidence for Anglo - Saxon settlement within the pagan period in Cheshire or Lancashire " . In any case , the sea would have been the primary means of travel and trade in this period . It also seems unlikely that Æthelfrith was protecting Anglian settlers in the area . Instead Æthelfrith may have been planning to attack Powys . The fact that he attacked the monks first , and only secondly the defending army , may perhaps be explained as a ruse to throw the defence into disarray .