870 King Alfred the great became king

England
Bagsecg and his viking raiders conquered East Anglia; they destroyed  the abbey of Ely and the monastery of Peterborough.
The vikings now controlled East Anglia, Northumbria and most of Mercia. Now the vikings attacked, the strongest of the 4 English kingdoms: Wessex.
King Alfred the great
Iceland
Norwegian settlement of Iceland and Faroe islands began. evidence suggests that approximately 60% of the Icelandic maternal gene pool is derived from Scotland and Ireland, which is much higher than other Scandinavian countries, although comparable to the Faroe Islands
Scotland
Olaf Cuaran and Ívar Boneless beseiged the Welsh stronghold of Alcluith, which fell after four months to the attackers.

The Dublin vikings destroyed the Stratchlyde capital so they could control the Dublin-York trade route and besieged Dumbarton, they left with thralls and loot, an attack which was recorded by Irish and Welsh annals.
"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. "

Ragnvald of Møre became the first earl of Orkney.