This is the first five years past the POD, just to give you an idea where I'm going. This isn't the final version, and I welcome any questions or comments.
Secondly, does anyone have a good map or source about the political situation in Ireland at the time? I'm very confused by just where exactly all these Irish kingdoms are, and which ones are current at the time of writing.
865 AD Danish raiders first began to settle in England. Led by brothers Halfdan and Ivar the Boneless, they wintered in East Anglia, were they demanded and received tribute in exchange for a temporary peace. From there they moved north and attacked Northumbria, which was in the midst of a civil war between the deposed king Osbert and a usurper Aelle. The Danes used the civil turmoil as an opportunity to capture York, which they sacked and burned.
867 AD Following the loss of York, Osbert and Aelle formed an alliance against the Danes. They launched a counterattack, but the Danes killed both Osbert and Aelle and set up a puppet king on Northumbrian throne. In response, King Ethelred of Wessex, along with his brother Alfred (the future King Alfred of England) marched against the Danes. Who were positioned behind fortifications in Nottingham, but were unable to draw the Danes into battle. In order to establish peace, King Burhred of Mercia ceded Nottingham to the Danes in exchange for leaving the rest of Mercia undisturbed.
869 AD Ivar the Boneless returned and demanded tribute from King Edmund of East Anglia.
870 AD King Edmund refused, Ivar the Boneless defeated and captured him at Hoxne and brutally sacrificed his heart to Oden through the use of the so-called “Blood Eagle ritual”, in the process adding East Anglia to the area controlled by the invading Danes. King Ethelred and Alfred attacked the Danes at Reading, but were repulsed with heavy losses. The Danes pursued them.
Norse-Irish warlord Olaf The White (Amlaib Conung) captures Alt Clut, the stronghold of the Britonnic kingdom of Strathclyde, a siege which lasted some four months and led to the destruction of the citadel and the capture of a very large number of captives. The siege and capture are reported by Welsh and Irish sources, and the Annals of Ulster say that in 871, after overwintering on the Clyde:
“Amlaíb and Ímar returned to Áth Cliath (Dublin) from Alba with two hundred ships, bringing away with them in captivity to Ireland a great prey of Angles and Britons and Picts.”
The Annals also suggest that the king of Strathclyde was among the victims.
Strathclyde at this point was precariously balanced between the Irish of Ulster, the Norse-Irish of the Hebrides, Galloway, and Dublin, the Danish puppet kingdom of Bernicia, and the Picts of Alba.
Olaf was a close ally of Ivar the Boneless, who had assisted him in defeating Ketil Flatnose of the Hebrides in Munster.
871 AD [POD] On January 7, Ethelred and Alfred met the Danish army at Ashdown. The West Saxon army was surrounded and obliterated. Both Ethelred and Alfred perished in the battle, sparing them death by Blood Eagle.
With the West Saxon threat eliminated, the Danes turned north against Mercia, capturing London and overrunning the kingdom. King Burhed of Mercia fled to Wessex, where he rallied the West Saxons and the surviving Mercians behind him. The Danes named a Saxon noble called Ethelbald king of Mercia and his brother Ethelbert king of Wessex, but Ethelbert remained in Mercia instead of entering “his” kingdom.
872 AD Ivar the Boneless dies and is succeeded by Guthrum the Old as leader of the Danes in England. Guthrum leads an army against the remnant Saxons in Wessex, and captures half the kingdom, but is defeated at Exeter. Mercia and Eastern Wessex rise up in revolt.
874 AD The English revolt within Danish-controlled territory finally suppressed, the Danes launch another attack Kent and Essex, which succumb quickly. All of England west of the River Exe is now in Danish hands. Burhred of Mercia is murdered in his sleep by a West Saxon noble named Odda, who makes a treaty with Guthrum, declaring him to be “Lord of the Western Isles” and the king of Wessex to be his vassal.
The Norse lords of all Britain assemble at Leicester.
Guthrum is acclaimed by all present as High King of Britain, ruling directly over the old kingdom of Mercia from Leicester. Halfdan Ragnarsson is named king of York, ruling all of Britain east of the Pennines from the Humber to the Firth of Forth. Hubbe the Generous is named king of London, ruling the southeastern part of Britain.
Olaf the White of Dublin is declared to be overlord of the Isles (Orkney, Shetland, the Hebrides, and Man) and Strathclyde, as well as the Norse settlements in Ireland.
Not present are the kings of Alba, the Welsh kingdoms or any of the native Irish kings.
Ingólfur Arnarson makes first permanent Norse settlement on Iceland.
875 Vikings attack Anglesey in the kingdom of Rhodri the Great, king of the greater part of Wales. The Welsh are driven from Anglesey, which becomes a domain of the King of the Isles.
Aed Finliath of Ailech and Cerball of Osraige invade Leinster, whose king, Cellach mac Dunchad, calls on the Norse for aid. A Norse/Irish army defeats Aed Finliath at Cluain Dolcáin and capture Tara, traditional seat of Ireland’s High Kings, overwintering in Meath.
876 Rhodri the Great conquers Dyfedd, the last independent Welsh kingdom.
Internal struggle within remnant Wessex between native English, refugees, and still-independent Cornwall under King Dungarth. Dungarth calls on High King at Leicester and Rhodri for aid, and Cornwall west of the Tamar is confirmed by Guthrum as an independent vassal of the “King of the Britons”. Both Guthrum and Rhodri assume this title refers to them.