Viking raid warfare and tactics
Vikings were members of tribes, originally from Scandinavia, of Norse ancestry, who gained a reputation for their raids and piracy in many parts of Europe, especially England, Ireland, and Frankish territories. The term "Viking Age" refers to the period roughly from 793 AD to the late 11th century in Europe. In this era Viking activity started with raids on Christian lands in England and eventually expanded to mainland Europe, including parts of present-day Russia. While maritime battles were rare, Viking bands proved very successful in raiding coastal towns and monasteries due to their efficient warships, and intimidating war tactics, skillful hand-to-hand combat, and fearlessness. What started as Viking raids on small towns transformed into the establishment of important agricultural spaces and commercial trading-hubs across Europe through rudimentary colonization. Vikings' tactics in warfare gave them an enormous advantage in successfully raiding (and later colonizing), despite their small population in comparison to that of their enemies.
Horik II
During Horik's reign, Vikings raided England in 855 and 860 with varying success. The Great Heathen Army arrived to East Anglia in 865 and conquered York in Northumbria two years later, starting the Viking conquest and colonization of much of northeast England. While they are expressly called Danes in the Anglo-Saxon Chronicle, the army appears to have been formed by Vikings operating in Francia and Frisia. Whether the royal power in Denmark had part in the planning and organization is unknown. Later sagas assert that this was the case, depicting the leaders of the invasion as sons of the Danish king Ragnar Lodbrok. However, no such king is known in the contemporary sources. The invasion leaders Halfdan and Bagsecg were known as "kings" and may or may not have been related to the kings in the Danish homeland.