The Story of Norway by Hjalmar Hjorth Boysen

The Norsemen had up to the middle of the eighth century played no part in the world's history. Their very existence had been unknown or but vaguely known to the rest of Europe. But towards the close of the eighth century they broke like a destructive tempest over the civilized lands, spreading desolation in their path. When their fast-sailing ships with two square sails were sighted at the river-mouths, people fled in terror, and the priests prayed in vain: "Deliver us, O Lord, from the rage of the Norsemen."

There were several reasons for this sudden warlike activity on the part of the Norsemen. They had waged war from immemorial times; because war was with them the most honorable occupation. As Tacitus says of their kinsmen, the Germans: "They deemed it a disgrace to acquire by sweat what they might obtain by blood. " But previous to the viking period they had fought each other. One earl or king made foraging expeditions into the land of his neighbors, and carried away with him whatever booty he could lay hands on. But in this perpetual warfare one or the other must at length become exhausted, and the stronger would be likely to oust or vanquish the weaker. This was what happened in the north. Large tracts of land, made up of small conquered kingdoms, were united under one successful chief, who, of course, made haste to prevent depredations within his own boundaries.