The Anglo-Saxon Kingdoms to c. 800

757
King Æthelbald of Mercia is murdered in a palace coup and briefly succeeded by one Beornred, who is in turn ousted by Æthelbald's distant cousin Offa – King Sigeberht of Wessex is driven from power in favour of Cynewulf

758
King Eadberht of Northumbria abdicates in favour of his son Oswulf – King Cynewulf of Wessex takes Berkshire from Mercia and launches a war against the Welsh

759
King Oswulf of Northumbria is murdered – A severe winter strikes England

760
Construction of Offa's Dyke is said to have begun, a large linear earthwork of some 240 kilometres along the border of Mercia and the Welsh kingdoms, although this is challenged by more recent research which places construction sometime in the 5th century

764
Offa of Mercia conquers and subjugates Kent

772
Offa of Mercia subjugates Sussex

776
King Egbert II of Kent defeats the Mercian army of Offa at the Battle of Otford, taking the kingship of Kent

779
Offa of Mercia defeats Cynewulf of Wessex at the Battle of Bensington – Charlemagne writes Offa a letter

785
Offa retakes Kent and drives out his rival Egbert II

786
Cynewulf of Wessex is killed – Offa supports Beorhtric as new king of Wessex

787
Offa of Mercia and Beorhtric of Wessex call the Synod of Chelsea in Kent – Offa persuades the Papacy to make Lichfield the seat of an archbishopric – Offa makes the archbishop of Lichfield crown his son Ecgfrith as king of Mercia to secure the succession

788
King Ælfwald of Northumbria is murdered

789
Beorhtric of Wessex marries the daughter of Offa of Mercia, allying Wessex to Mercia – Vikings first appear and raid Portland, as recorded in the Anglo-Saxon Chronicle

790
The Anglo-Saxon scholar and clergyman Alcuin returns to the British Isles after an extended stay at the court of Charlemagne – King Æthelred I returns to Northumbria after 11 years of exile – Offa of Mercia takes control of East Anglia

792
Æthelred of Northumbria marries the daughter of Offa of Mercia, allying Northumbria with Mercia – Offa prepares coastal defenses against Viking attacks

793
8 June: Vikings raid the Northumbrian coast and sack the monastery of Lindisfarne, the first Viking attack on a monastery in the British Isles

794
King Æthelberht II of East Anglia visits the Mercian court but is killed by order of Offa – The Vikings destroy Monkwearmouth and Jarrow

795
Offa of Mercia receives gifts from Charlemagne – Offa refounds St. Albans Abbey

796
Æthelred of Northumbria is murdered, plunging the kingdom into chaos – Offa of Mercia and Charlemagne make a trading agreement – Offa dies after a reign of 39 years during which he subjugated Kent, Essex, Sussex and East Anglia (Mercian Supremacy) – Offa is buried at Bedford

797
Welsh attacks on Mercia

798
King Coenwulf of Mercia invades Gwynedd and also defeats Kent – Battle of Billington: king Eardwulf of Northumbria avenges the murder of former king Æthelred

801
Eardwulf of Northumbria invades Mercia

802
King Beorhtric of Wessex dies of poison and is succeeded by Egbert

=========