Timeline (Ethelred the Pious)

Ninth Century

 * 871: At the Battle of Ashdown, Halfdan Ragnarsson leads a great army of Danes into the territory of the Anglo-Saxon Kingdom of Wessex. King Ethelred of Wessex lingers at his morning devotions and his brother Alfred does not take command of the Saxon army, giving the Danes time to seize the high ground and the initiative.  The Saxons are routed.  Halfdan declares himself King of Lundun and Jorvik.
 * 871-872: Ethelred makes a series of counterattacks, some successful, but most of them not. He and his forces are driven into Kent.
 * 873: The Battle of Headcorn (Kent) is the last stand of the Wessex kingdom, and by extention of the Anglo-Saxon rulers of England. Ethelred is killed.  Alfred assumes the kingship and goes underground.
 * 877: Halfdon removes the puppet king Ceolwulf II of Mercia from his throne, adding the remainder of English Mercia to his territory. Mercia is divided among Halfdon's loyal jarls.
 * 881: Alfred is captured and killed, ending major Saxon resistance to Viking rule in England.
 * 897: Hvitserk Halfdansson proclaims the Angelagen, or English Law, in the southern part of the Kingdom of Jorvik (Mercia, Wessex, and Kent). It preserves many of the Anglo-Saxon legal concepts, including the concept of ruling based on legal precedent.
 * Growing conflict between the Kingdoms of Jorvik and Østangeln (East Anglia), led by descendants of the brothers Halfdan and Ivar Ragnarsson.

Tenth Century

 * Massive immigration from Denmark and Norway
 * Norwegian invaders take advantage of the conflict between Østingeln and Jorvik.  Østingeln  falls to Norwegian adventurers, creating a united kingdom of Østingeln, Man, and Dublin.