822 Vikings attacked the coast of Ireland

Glavendrup stone from 900-925
Heathen runestone. the inscription tell us "Ragnhild placed this stone after all of her honourable guardians. All the sons made these runestones after their father and his wife, but Sote created theses runes after the command of his master, Thor blessed these runes. The person who vandalize or steals this stone, will be punished harsh.
Charlemagne sent a diplomatic mission to Denmark (822-823) led by the Archbishop of Rheims Ebo.
Seal of Charlemagne
The Vikings reached Cork. Norwegian vikings had launched the first series of attacks on the East coast of Ireland.