Historians have theorized a number of factors contributing to the Viking expansion from the 8th to 11th centuries.
Most historians place the onset of the Viking Age in the 8th century C.E. when Scandinavian pirates began to attack the coasts of western Europe, including the violent assaults on churches and monasteries that gave rise to the reputation of the Vikings as bloodthirsty warriors. There is, however, no general agreement among historians about the causes of the Viking expansion beyond Scandinavia. Instead, historians identify a number of different causes during specific phases of the Viking expeditions as well as in specific regions of Scandinavia. Some of the key causes identified include over-population, climate change, internal political strife, the desire for honour and loot, and politics abroad.
Who Were the Vikings?
The term ‘Viking,’ meaning “one who fights at sea” or “warfare at sea” in West Nordic, is still used today to describe the peoples of Denmark, Norway, and Sweden who attacked, looted, traded with, and ultimately settled in western and eastern Europe, as well as the Scandinavians who adventured to Iceland, Greenland, and North America, between the 8th to 11th centuries. The term is actually an inaccurate label for the inhabitants of these Scandinavian countries during the Viking Age because it implies uniformity between the peoples of these regions. The inhabitants of Denmark, Norway, and Sweden were unique groups of people who had different motives for expanding beyond Scandinavia.
Contemporary literary sources, such as the cleric Dudo of Normandy, make outlandish claims about the Vikings and are not likely accurate. However, although most historians would not consider Dudo’s claim that the Vikings engaged in “shameless and unlawful intercourse” to “breed innumerable progeny,” some historians have not discounted the explanation of population pressure as a possible cause for the Viking expansion.
In A History of the Vikings, for example, Gwyn Jones highlights persistent overpopulation and a shortage of land, not as a result of rampant and immoral Norse polygamy as Dudo would have us believe, but due to accepted Scandinavian social practices: “Great men had wives by marriage-contract and, if they wished, by loose-bridal. For any save the very poor a quiverful of sons was welcome. They were proof of a man’s virility.” A “quiverful” of sons would, of course, have to be provided for and this could have placed significant pressure on chieftains and farmers, in terms of providing adequate resources to their sons.
Henry R. Loyn also suggests that population pressure combined with climate change may have played an important role in one specific phase of the Viking invasions. Although the Viking Age as a whole is thought to have been a warm and dry period, Scandinavia experienced a cold spell from c. 860 to c. 940, which corresponds to an important period of Viking settlement in Britain. This climate change, making already difficult living conditions even harsher in the North, combined with population pressure from an earlier period of prosperous farming and milder climate, may well have contributed to the first phase of the Viking expansion, in particular, the Norwegian colonization of the British Isles and the islands of the North Atlantic.
Internal Political Strife
In 13th-century Icelandic literary sources, however, a significant force contributing to the Viking migration was not population pressure or climate change, but rather royal tyranny or escape from other forms of internal political strife. Royal tyranny, in fact, may have been a significant motivation for Norwegian migration during the reign of King Harald Sigurdsson, or Harald the Ruthless, during the 12th century. In King Harald’s Saga, from Snorri Sturluson’s Heimskringla, for instance, Sturluson describes the harsh action King Harald takes against farmers who withheld their dues and taxes and supported his enemies during a rebellion: “So the king had the farmers seized; some of them he ordered to be maimed, others killed, and most of them deprived of all their possessions. All those who could escape fled.” Internal political strife may have had an impact on other Scandinavians as well, such as the Danish during the reign of King Godfred in the early 9th century.
Honour and Loot
Other literary and archaeological sources, namely scaldic poems and rune stones, identify honour and loot as the main driving forces behind the Norse invasions. Viking expeditions in search of honour and booty would have allowed men who had lost their fortunes to regain their wealth and status. The expeditions may also have been particularly attractive to the sons of large families, who could use such expeditions to obtain the status and wealth that could not be obtained at home. War and trade overseas provided the Vikings with the precious goods, slaves, and other material goods to make their status achievements a reality in their homelands or in their new settlements.
Political upheaval outside of Scandinavia may also have contributed to the Viking expansion. The Frankish kingdom in particular, as it expanded northwards after c. 770, may have been a contributing factor in the Danish expansion beyond Scandinavia. The politically unstable Frankish empire, characterized by continual feuding of successor princes, became an easy target for the Viking attackers. Once the Vikings were able to penetrate the empire, they began to settle on the Continent and established a powerful kingdom in Normandy. The Vikings also took advantage of political instability in Ireland and England in a similar fashion.