What was the reason for Viking expansion? The commonly held view is that population pressures in Scandinavia led to an expansion far and wide. And this is an attractive theory that goes a long way to explain the the great number of Viking merchants, raiders and war-lords who left Scandinavia to seek fortunes and land. There certainly was a rise in population in the eighth and ninth centuries AD, probably due to improving climatic conditions and developments in agriculture, such as the introduction of a heavier type of plough. So, population increase did play a part in expansion, but there were also other reasons.

For one thing, the picture of a land totally full up does not sit with the fact that many slaves were brought back to Scandinavia during this time. Abbo commented that the Vikings "seize the country people, bind them and send them across the sea." Many of these were traded all over Europe, but a good number must have ended up in Scandinavia. There is thus good reason to believe that Denmark, for example, could accomodate an increase in population.

The larger issue, then, is perhaps not the absolute number of people but land ownership. Was there enough land to go round for all the freemen? (And by 'freemen' we may be talking about a small proportion of the population, perhaps under 5%.) Many local chieftans may well have found their sphere of influence dwindling as spare land was snapped up. And by the ninth century, rich pickings further afield were to be had by enterprising war-lords. Silver coins from the Abbasid Empire have been found in Scandinavia from the early 800s. Also, the rich trading centres of their neighbours, such as Hamburg or Dorestad, offered wealth if one had the means to grab it. Peter Sawyer points out that demands for goods from western Europe "encouraged Scandinavians to search for new supplies in the far north or east of the Baltic." ('The Causes of the Viking Age', PH Sawyer in The Vikings ed. RT Farrell.) Trade with their near neighbours opened up yet more opportunities. To return to the issue of slaves, I believe it is recorded in some of the sagas that Norse freemen left slaves to maintain their farms, while they sailed in spring to trade or conduct raids. So, population pressures allowed expansion but did not necessarily force expansion.

There was another pressure on the outward expansion of the Vikings, however. This was political pressure from within. Denmark in particular was coming under the power of a single king. The construction of the Kannhave canal in the eighth century shows the existence of a powerful royal figure - in the same way that Offa's Dyke does in England. However, this was not without struggle. Frankish annals first record civil wars within Denmark from 812. The Annals of Fulda record that in 854 Horik I of Denmark died in a civil war provoked by a nephew of his who had failed to gain a share of power. This nephew had become an exile dependent on piracy until he returned to claim Denmark once more. So, during this period of power struggle those who lost out took to the seas and Europe was faced with these marauders. But once the Jelling dynasty had established its control over Denmark, it was increasingly the Danish kings who carried out aggressive policies abroad. The kings followed in the pattern of Norse activity that had already been established.

So the reasons for Viking expansion form something of a patchwork. Trade had brought the wider world within view and within reach; population increases had encouraged ambitious lords to seek fortunes elsewhere; lords were able to embark on raids in the summer months while slaves tended their lands; power struggles had forced out exiles into Europe; and centralisation of power had created kings who were capable of leading large armies to Frankia and England.