The Rus’ Siege of Constantinople occurred in AD 860, in which Byzantine and Western European sources document an expeditionary force of the Rus' Khaganate that tried to conquer the centre of the Byzantine Empire.
The Great Heathen Army was a coalition of Viking warriors that invaded England in AD 865, which according to lore was in response to the death of the legendary figure Ragnar Lodbrok, at the hands of King Ælla of Northumberland.
St. Brice's Day refers to an event that took place in Saxon England under the rule of Æthelred II, also known as “Æthelred the Unready”, that led to the extermination of Danes in the English realm.
A trelleborg or ring fort was a circular fortification built across Denmark and Sweden during the Viking age. Similar structures have been found throughout Northern Europe, particularly in Ireland, but none have the same strict and precise geometrical design of the Scandinavian ring fortresses.