The period of Scandinavian history to which the term Viking is applied extends roughly from the middle of the 8th to the end of the 10th or the first half of the 11th century. Its commencement was marked by the raids of Scandinavian freebooters upon the coasts of England, Western Scotland and Ireland and upon Frankish territory. Its climax was reached when in the course of the 9th and 10th centuries Scandinavian rule was established in Ireland, Man and the Western Islands, the northern and midland districts of England, Normandy, and a great part of Russia. Its close was marked by the consolidation of the Scandinavian kingdoms in the late 10th and early 11th centuries under such mighty sovereigns as Olaf Tryggvason and Olaf the Holy in Norway, Olaf SkÖtkonung in Sweden, and greatest of all, king Knut in Denmark, who for a brief time united the whole of Scandinavia and a great part of the British Isles in one vast confederacy.

The extent and importance of the movement is indicated from the first by the almost simultaneous appearance of trouble in England, on the coast of France, and on the Eider boundary between Denmark and the Frankish empire.

In the reign of Beorhtric, king of Wessex (786-802), three ships of the Northmen coming from HÖrÐaland (around Hardanger Fjord) landed near Dorchester, in June 793 Lindisfarne was sacked, in March 800 Charlemagne found himself compelled to equip a fleet and establish a stronger coastguard to defend the Frankish coast against the attacks of the Northmen, and from 777 onwards, when the Saxon patriot Widukind took refuge with the Danish king Sigefridus (O.N. SigrÖÐr), there was almost constant friction along the land-boundary between Denmark and the Frankish empire.

This outburst of hostile activity had been preceded by considerable intercourse of a varied character between Scandinavia and the countries of Western Europe. Early in the 6th century the Danes or, according to another authority, the GÖtar from GÖtaland in south Sweden, invaded Frisia under their king Chocilaicus. Reference is made to this raid in the story of Hygelac, king of the Geatas, in Beowulf. Professor Zimmer suggested that the attacks of unknown pirates on the island of Eigg in the Hebrides and on Tory Island off Donegal, described in certain Irish annals of the 7th century, were really the work of Scandinavian raiders. The evidence of Irish legend and saga goes to prove that in the same century Irish anchorites settled in the Shetlands but were later compelled by the arrival of Scandinavian settlers to move on to the lonely Faroes. Here they were not to be left in peace, for the Irish geographer Dicuil, writing in 825, tells us that the Faroes had then been deserted by the monks for some thirty years owing to the raids of Northmen pirates. Dr Jakobsen has shown that the forms of place-names in the Shetlands point very definitely to a settlement from Scandinavia in pre-Viking days—before 700—while the sculptured stones of Gothland show already at the end of the 7th century clear evidence of Celtic art influence. Possibly also merchants of Scandinavian origin were already settled in the Frankish empire and it is certain that there was considerable trade between Scandinavia and the West.

Most of the intercourse thus demonstrated was slow in development, peaceful and civilising in character. How came it that in the later years of the 8th century this intercourse was suddenly strengthened and intensified, while at the same time it underwent a great change both in methods and character?

The traditional explanation is that given by Dudo and by William of JumiÈges in their histories of the settlement of Normandy and by Saxo in his account of Danish settlements in Baltic lands in the 10th century, viz. that the population of Scandinavia had outgrown its means of support and that enforced emigration was the result. There may be a certain element of truth in the tradition but when it says that this excess of population was due to polygamy we have every reason to doubt it. Polygamy does not lead to an over-rapid growth of population as a whole, and it is fairly certain that it was practised only by the ruling classes in Scandinavia. It is quite possible, however, that the large number of sons in the ruling families made it necessary for the younger ones to go forth and gain for themselves fresh territories in new lands.

A clearer light is perhaps thrown on the matter if we examine the political condition of the Scandinavian countries at this time. In Norway we find that the concentration of kingly authority in the hands of Harold Fairhair after the middle of the 9th century led many of the more independent spirits to leave Norway and adopt a Viking life in the West or to settle in new homes in Iceland. So strong was the spirit of independence that when Harold Fairhair received the submission of the Vikings of the West after the battle of Hafrsfjord, many of them rather than endure even a shadowy overlordship abandoned their Viking life and settled down to peaceful independence in Iceland. It is quite possible that earlier attempts at consolidation on the part of previous petty Norwegian kings may have had similar results.

Of the condition of Sweden we know practically nothing but we have sufficient information about the course of events in Denmark at this time to see that it probably tended to hasten the development of the Viking movement. Throughout the first half of the 9th century there were repeated dynastic struggles accompanied probably by the exile, voluntary or forced, of many members of the rival factions.

External causes also were certainly not without influence. From the 6th century down to the middle of the 8th, the Frisians were the great naval and trading power of North-West Europe. They had probably taken some part in the conquest of England and, during the 7th and 8th centuries, the whole of the coast of the Netherlands from the Scheldt to the Weser was in their hands. Their trade was extensive, their chief city being Duurstede a few miles south-east of Utrecht. The northward expansion of the Franks brought them into collision with the Frisians in the 7th century. The struggle was long and fierce but in the end the Frisians were defeated by Charles Martel in 734 and finally subjugated by Charlemagne in 785. The crushing of Frisian naval power and the crippling of their trade probably played no unimportant part in facilitating the Scandinavian advance, and it is curious to note that while there is considerable archaeological evidence for peaceful intercourse between the west coast of Norway and Frisian lands in the 8th century, that evidence seems to come to an end about the year 800, just when Frisian power finally declined. There can be no doubt also that the conquest of the Saxons by Charlemagne at the close of the 8th century, bringing Franks and Danes face to face along the Eider boundary, made the latter uneasy.

There has been much arguing to and fro of the question as to the respective shares taken by Danes and Norwegians in the Viking movement. That of the Swedes can fortunately be determined with a good deal more certainty. The Swedes were for the most part interested only in Eastern Europe and there by way of trade rather than of battle: we learn from runic inscriptions and other sources that some Swedes did visit England and the West, but these visits were due to individual rather than national activity. The question as between Dane and Norwegian has been to some extent made more difficult of settlement through the national prejudices of Scandinavian scholars; e.g. Danes for the most part decide in favour of the Danish origin of Rollo of Normandy, while Norwegians decide in favour of his Norwegian birth. Such differences of opinion are unfortunately only too often possible owing to the scantiness of the material upon which we have to base our conclusions. Medieval chroniclers were for the most part unable or unwilling to distinguish between Danes and Norwegians; they were all alike 'Nordmanni' to them and the term 'Dani' is practically interchangeable with it. The vagueness of their ethnographical knowledge is manifest when we find the Norman Dudo at the beginning of the 11th century tracing back the Dani (or Daci) to an original home in Dacia. The Irish annalists did, however, draw a very definite distinction between Norwegians and Danes—Finn-gaill and Dubh-gaill as they called them, i.e. White and Black Foreigners respectively[2]. They seem never to confuse them, but exactly on what grounds they gave them their distinguishing epithets it is now impossible to determine. They do not correspond to any known ethnographical differences, and the only other reasonable suggestion which has been offered is that the terms are used to describe some difference of armour or equipment as yet unknown to us. The Irish annals also distinguish between Daunites or Danes and Lochlanns or men from Lochlann, i.e. Norway; but again the origin of the term Lochlann as applied to Norway is obscure. The writers of the Anglo-Saxon Chronicle seem to use the term NorÐmenn very definitely of Norwegians, just as Alfred does in his translation of Orosius, but the term Dene came to be used more vaguely and uncertainly. It is only very rarely that the chroniclers vouchsafe us precise information as to the home of any particular group of Viking raiders. We have already mentioned the presence of Norwegians from HÖrÐaland in England at the very opening of the movement[3]: once we hear of 'Westfaldingi,' i.e. men from Vestfold in South Norway, in an account of attacks on Aquitaine, and in one passage the Vikings are called 'Scaldingi,' but it is disputed whether this means Vikings who had been quartering themselves in the valley of the Scheldt, or is a term applied to the Danes from the name of their royal family, viz. the SkjÖldungar[4]. Speaking roughly we may however assert that Ireland, Scotland and the Western Islands were almost entirely in the hands of Norwegian settlers (Danish attacks on Ireland failed for the most part). Northumbria was Norwegian, but East Anglia and the Five Boroughs were Danish. The attacks on France and the Netherlands were due both to Norwegians and Danes, probably with a preponderance of the latter, while Danes and Swedes alone settled in Baltic lands.