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.