Two great streams of Northern immigration met on the shores of Britain during the ninth, tenth, and eleventh centuries. The Norsemen from the deep fiords of Western Norway, fishing and raiding along the coasts, pushed out their adventurous boats into the Atlantic, and in the dawn of Northern history we find them already settled in the Orkney and Shetland Isles, whence they raided and settled southward to Caithness, Fife, and Northumbria on the east, and to the Hebrides, Galloway, and Man on the western coast. Fresh impetus was given to this outward movement by the changes of policy introduced by Harald Fairhair, first king of Norway (872–933). Through him a nobler type of emigrant succeeded the casual wanderer, and great lords and kings’ sons came over to consolidate the settlements begun by humbler agencies. Iceland was at the same time peopled by a similar stock. The Dane, contemporaneously with the Norseman, came by a different route. Though he seems to have been the first to invade Northumbria (if Ragnar and his sons were really Danes), his movement was chiefly round the southern shores of England, passing over by way of the Danish and Netherland coast up the English Channel, and round to the west. Both streams met in Ireland, where a sharp and lengthened contest was fought out between the two nations, and where both took deep root, building cities and absorbing much of the commerce of the country.

The Viking was at first simply a bold adventurer, but a mixture of trading and raiding became a settled practice with large numbers of Norsemen, who, when work at home was slack and the harvest was sown or reaped, filled up the time by pirate inroads on their own or neighboring lands. Hardy sailors and fearless fighters they were; and life would have seemed too tame had it meant a continuous course of peaceful farming or fishing. New possessions and new conquests were the salt of life.