Æthelred of Mercia Æthelred ( ; died after 704 ) was King of Mercia from 675 until 704 . He was the son of Penda of Mercia and came to the throne in 675 , when his brother , Wulfhere of Mercia , died . Within a year of his accession he invaded Kent , where his armies destroyed the city of Rochester . In 679 he defeated his brother - in - law , Ecgfrith of Northumbria , at the Battle of the Trent : the battle was a major setback for the Northumbria ns , and effectively ended their military involvement in English affairs south of the Humber . It also permanently returned the kingdom of Lindsey to Mercia ' s possession . However , Æthelred was unable to re - establish his predecessors ' domination of southern Britain . He was known as a pious and religious king , and he made many grants of land to the church . It was during his reign that Theodore , the Archbishop of Canterbury , reorganized the church ' s diocesan structure , creating several new sees in Mercia and Northumbria . Æthelred befriended Bishop Wilfrid of York when Wilfrid was expelled from his see in Northumbria ; Æthelred made Wilfrid Bishop of the Middle Angles during his exile and supported him at the synod of Austerfield in about 702 , when Wilfrid argued his case for the return of the ecclesiastical lands he had been deprived of in Northumbria . Æthelred ' s wife , Osthryth , was a daughter of King Oswiu , one of the dominant 7th - century Northumbrian kings . Osthryth was murdered in unknown circumstances in 697 , and in 704 Æthelred abdicated , leaving the throne to Wulfhere ' s son Coenred . Æthelred became a monk at Bardney , a monastery which he had founded with his wife , and was buried there . Ceolred , who was Æthelred ' s son ( though apparently not by Osthryth ) , became king after Coenred ; it is also possible that Æthelred had another son named Ceolwald who was briefly king before Ceolred . Mercia in the seventh century . By the 7th century , England was almost entirely divided into kingdoms ruled by the Anglo - Saxons who had come to Britain two hundred years before . The kingdom of Mercia occupied what is now the English midlands . The origin of the kingdom is not recorded , but royal genealogies preserved in the " Anglo - Saxon Chronicle " and the Anglian collection agree that the royal houses were descended from a founder named Icel ; the Mercian royal house is hence known as the Iclingas . The earliest Mercian king about whom definite historical information has survived is Penda of Mercia , Æthelred ' s father . The larger neighbouring kingdoms included Northumbria to the north , recently united from its constituent kingdoms of Bernicia and Deira , East Anglia to the east , and Wessex , the kingdom of the West Saxons , to the south . According to " Ecclesiastical History of the English People " , a history of the English church written by the 8th - century monk Bede , there were seven early Anglo - Saxon rulers who held " imperium " , or overlordship , over the other kingdoms . The fifth of these was Edwin of Northumbria , who was killed at the battle of Hatfield Chase by a combined force including Cadwallon , a British king of Gwynedd , and Penda . After Edwin ' s death , Northumbria briefly fell apart into its two subkingdoms of Bernicia and Deira . Within a year Oswald , Edwin ' s nephew , killed Cadwallon and reunited the kingdoms , subsequently re - establishing Northumbrian hegemony over the south of England . In 642 Penda killed Oswald at the battle of Maserfield , and Northumbria was again divided . Oswald ' s son Oswiu succeeded to the throne of Bernicia , and Osric ' s son Oswine to Deira , the southern of the two kingdoms . In 655 , Oswiu defeated and killed Penda at the Battle of the Winwaed . Oswiu installed Peada , a son of Penda , as king of southern Mercia and ruled the northern half himself ; after Peada was murdered in 656 Oswiu took direct control of all of Mercia . A coup in 658 threw off Northumbrian overlordship and established Wulfhere as king . By the early 670s , Wulfhere had become the most powerful king in southern Britain , with an effective hegemony over all the Anglo - Saxon kingdoms except for Northumbria . The main source for this period is Bede ' s " History " , completed in about 731 . Despite its focus on the history of the church , this work also provides valuable information about the early Anglo - Saxon kingdoms . For Wessex and Kent , Bede had informants who supplied him with details of the church ' s history in each province , but he appears to have had no such contact in Mercia , about which he is less well - informed . A further source for this period is the " Anglo - Saxon Chronicle " , compiled at the end of the 9th century in Wessex . The " Chronicle " ' s anonymous scribe appears to have incorporated much information recorded in earlier periods . Ancestry and early reign . Æthelred was the son of Penda of Mercia . Penda ' s queen , Cynewise , is named by Bede , who does not mention her children ; no other wives of Penda are known and so it is likely but not certain that she was Æthelred ' s mother . The " Anglo - Saxon Chronicle " gives Penda ' s age as fifty in 626 , and credits him with a thirty - year reign , but this would put Penda at eighty years old at the time of his death , which is generally thought unlikely as two of his sons ( Wulfhere and Æthelred ) were young when he was killed . At least as likely is that Penda was fifty years old at his death , rather than at his accession . Æthelred ' s date of birth is unknown , but Bede describes Wulfhere as a youth at the time of his accession in 658 , so it is likely he and Æthelred were in their middle teens at that time . The early sources do not say whether Æthelred was older or younger than Wulfhere . Nothing is known of Æthelred ' s childhood . He had another brother , Peada , and two sisters , Cyneburh and Cyneswith ; it is also possible that Merewalh , king of the Magonsæte , was Æthelred ' s brother . In 674 , according to Stephen of Ripon , Wulfhere " stirred up all the southern nations against [ Northumbria ] " , but he was defeated by Oswiu ' s son Ecgfrith who forced him to surrender Lindsey , and to pay tribute . Wulfhere survived the defeat , but died in 675 , possibly of disease , and Æthelred became king . The first recorded act of Æthelred ' s reign is in 676 , when his armies ravaged Kent , destroying Rochester , the seat of the bishops of West Kent . The reason for his attack is not recorded , but he may have wished to prevent King Hlothhere of Kent from regaining control of Surrey , which had been recently brought into the Mercian orbit by Wulfhere . It may also be that Æthelred wished for revenge for the murder of the sons of Eormenred of Kent ; the murders had been instigated by Ecgberht of Kent , Hlothhere ' s brother , and it is possible that Æthelred was the uncle of the murdered princes . A third suggestion is that the kings of Essex solicited the invasion , in response to recent Kentish attempts to gain dominance over the East Saxons . Regardless of the reason , Hlothhere was likely then forced to accept Æthelred ' s overlordship . The damage to the see of Rochester was so great that the incumbent bishop , Putta , retired from his diocese ; his appointed successor , Cwichelm , also gave up the see " because of its poverty " . Early in Æthelred ' s reign , Theodore , the Archbishop of Canterbury , began a substantial reorganization of the church in Mercia . In 675 he removed Winfred from his position as Bishop of Lichfield , and over the next four years he divided the vast Mercian see into the five dioceses of Leicester , Lichfield , Worcester , Dorchester and Hereford . Æthelred was a devout king , " more famed for his pious disposition than his skill in war " , and he made several gifts of land to the expanding church , including grants at Tetbury , Long Newton , and Somerford Keynes . There is also a tradition that Æthelred was associated with the founding of Abingdon Abbey , in southern Oxfordshire . Relations with Northumbria . Mercia had been in conflict with Northumbria since at least 633 , when Penda of Mercia defeated and killed Edwin of Northumbria at the Battle of Hatfield Chase . However , there were diplomatic marriages between the two kingdoms : Æthelred ' s sister Cyneburh married Alhfrith , a son of Oswiu of Northumbria , and both Æthelred and his brother Peada married daughters of Oswiu . Cyneburh ' s marriage to Alhfrith took place in the early 650s , and Peada ' s marriage , to Ealhflæd , followed shortly afterwards ; Æthelred ' s marriage , to Osthryth , is of unknown date but must have occurred before 679 , since Bede mentions it in describing the Battle of the Trent , which took place that year . Bede does not mention the cause of the battle , simply saying that it occurred in the ninth year of Ecgfrith ' s reign . He is more informative on the outcome . Ælfwine , the young subking of Deira , was killed ; Ælfwine was brother to Osthryth and Ecgfrith , and was well liked in both Mercia and Northumbria since Æthelred ' s marriage to Osthryth . According to Bede , his death threatened to cause further strife between the two kingdoms , but Theodore , the Archbishop of Canterbury , intervened : Theodore , the beloved of God , enlisting God ' s help , smothered the flames of this awful peril by his wholesome advice . As a result , peace was restored between the kings and peoples , and in lieu of further bloodshed the customary compensation was paid to King Ecgfrith for his brother ' s death . Æthelred took possession of Lindsey again after the battle ; the change in control this time was lasting , and Lindsey remained part of Mercia until the Viking invasion of the 9th century remade the map of England . Conflict between Northumbria and Mercia did not completely cease after this date : Scottish annals record that Æthelbald , an 8th - century Mercian king , ravaged Northumbrian territory in 740 while King Eadberht of Northumbria was absent fighting the Picts . However , the Battle of the Trent effectively ended Northumbrian involvement in southern Britain . A conflict between Bishop Wilfrid of York and the church and secular establishment led to Wilfrid ' s expulsion from Northumbria and the division of his vast diocese . After the death of Ecgfrith in 685 , Archbishop Theodore arranged a reconciliation between Wilfrid and Aldfrith , Ecgfrith ' s successor , but in 692 Aldfrith and Wilfrid fell out and Wilfrid went into exile in Mercia . Æthelred made Wilfrid bishop of the Middle Angles , and supported him at the Council of Austerfield in about 702 , when Wilfrid argued his case before an assembly of bishops led by Archbishop Berhtwald of Canterbury . Æthelred ' s support for Wilfrid embroiled him in dispute with both Canterbury and Northumbria , and it is not clear what his motive was , though it may be relevant that some of Wilfrid ' s monasteries were in Mercian territory . The southern kingdoms . Two charters of 681 show Æthelred granting land near Tetbury , on what is now the border between Gloucestershire and Wiltshire . This may indicate that Æthelred was able to extend Mercian influence further into the territory of the West Saxons , as Wulfhere had done before him . The West Saxons managed a significant military resurgence under Cædwalla , king of Wessex from about 685 to 688 , but when Cædwalla departed for Rome on pilgrimage there may have been internal strife before Ine , his successor , took the throne . Cædwalla had successfully conquered the kingdoms of Sussex and Kent , and his abdication may have contributed to the unsettled history of the southeast over the next few years . In Kent , Oswine emerged as king , though only in eastern Kent ; the western half of the kingdom was ruled by Swæfheard , son of Sæbbi , the king of Essex . It is possible that Æthelred provided support to both Swæfheard and Oswine ; for each king a charter survives in which Æthelred confirms land grants they made in Kent , and Æthelred ' s invasion of Kent in 676 indicates his opposition to the traditional Kentish royal house . A charter of Swæfheard ' s dated 691 is also of interest as it indicates that Æthelred had invaded Kent ; it has been suggested that Æthelred intended to place Wilfrid in the Archbishop ' s seat at Canterbury , but if so he was unsuccessful . Alternatively , Æthelred may have needed assistance in Kent from the East Saxons who may have been independent of Mercia for a decade or more by that time . The East Saxons did return to the Mercian orbit over the next few years : a charter of Æthelred ' s , dated between 693 and 704 , shows him granting land to Wealdhere , the bishop of London , and in 704 Æthelred consented to a grant made by Swæfheard . The latter charter also appears to show that a " comes " , or local official , was put in place by the Mercians to protect their interests . Despite this evidence of Mercian involvement in the southeast there is very little indication that Æthelred had expansionist ambitions to the south . The increasing strength of the West Saxons under Cædwalla and Ine would have limited Mercian opportunities in that direction . The Northumbrians were no longer a distraction ; they had been contained north of the Humber since the Battle of the Trent , and became even less of a threat after their disastrous defeat in 685 at the hands of the Picts . A possible explanation is that Æthelred was preoccupied with war with the Welsh . It was also at this time that the Hwicce came more definitely into the Mercian orbit . The last Hwiccean ruler to take the title of king was Oshere , who died in 685 ; but from the mid - 670s he sought Æthelred ' s consent for his grants , and Æthelred regarded him as a subking . Further evidence of Æthelred ' s involvement among the Hwicce comes from a charter in which he grants land for a minster in Gloucestershire , in Hwiccean territory ; the charter is generally thought to be a fabrication , but it appears to be based on an authentic earlier source . Abdication and final years . Osthryth was murdered in 697 , for reasons unknown ; according to Bede the murderers were " her own people , the Mercian chieftains " . Bede records that Peada ' s death , forty years earlier , stemmed from " the treachery , it is said , of his own wife " ; Peada ' s wife was Ealhflæd , Osthryth ' s sister . Hence Osthryth ' s murder may have been in revenge for Peada ' s assassination , though it has also been interpreted more directly as a sign of continuing hostility between Northumbria and Mercia . Osthryth was buried at Bardney in Lindsey , the monastery where , at her urging , the relics of her uncle , Oswald of Northumbria , were kept and revered , though evidence of resistance at Bardney to the cult of Oswald is also indicative of the poor relations between the two kingdoms . In 704 , Æthelred abdicated to become a monk and abbot at Bardney , leaving the kingship to his nephew Coenred . Seventh century Mercian rulers often patronised religious establishments outside the Mercian heartlands , perhaps as a way of gaining support in outlying provinces . Æthelred ' s and Osthryth ' s interest in Bardney is consistent with this pattern . The encouragement of the cult of royal saints in areas beyond the central Mercian lands also seems to have been a deliberate policy , and both Æthelred and Osthryth were later revered as saints at Bardney . It appears that Æthelred continued to have influence in the kingdom after his abdication : a passage in Stephen of Ripon ' s " Life of Wilfrid " shows Æthelred summoning Coenred to him and advising him to make peace with Wilfrid . The date of Æthelred ' s death is not recorded ; though it is known that he was buried at Bardney . Æthelred had at least one son , Ceolred . The medieval " Chronicon Abbatiae de Evesham " records that Ceolred was not the son of Osthryth , though it does not name Ceolred ' s mother . Ceolred succeeded to the throne in 709 , after Coenred abdicated in 709 to go to Rome on pilgrimage . One version of the regnal lists for Mercia shows a king named Ceolwald reigning after Ceolred , and it is possible that Ceolwald , if he existed , was also a son of Æthelred ' s .