Plundering expeditions are an aspect of the Scandinavian expansion of the VIII th -IX e centuries. It is due in particular to the formation of the Norwegian and Danish kingdoms, and to the contacts of these countries with the Carolingian world. The Vikings used trade routes they knew to conduct raids on Western Europe. The Danes preferred to go to England and the countries bordering the North Sea and the English Channel, while the Norwegians established trading posts in the islands north of Scotland, in Iceland and Greenland. The Swedes passed through the Baltic Sea, taking advantage of the great rivers of the Slavic countries to go up to Byzantium.
To the heart of the kingdoms
Danes and Norwegians, encouraged by the absence of military resistance from the Carolingian princes, attacked the coastal regions of the Atlantic Ocean and did not hesitate to go up the rivers to devastate the heart of the kingdoms. These raids adopted different rhythms and purposes over time. Thus, at the beginning of the IX
e
century, the raids were carried out by small bands of 10 to 20 ships, which made short stays and returned home with a booty of gold, silver, jewels and slaves. Then, emboldened by previous successes, the Vikings assembled larger and larger fleets:in 885, a fleet of 700 ships sailed up the Seine to Paris and remained there for more than a year.
Three different phases have been recognized in this Scandinavian expansion. From 800 to 850, the Vikings searched for gold and silver, which were mainly found in monasteries, churches and princely palaces. Once these riches were plundered, the Vikings adopted another technique, from 850 to 880, consisting in surrounding a city or a monastery and promising their departure after payment of a huge ransom. The third phase, from 880, led the Vikings to seek land to settle there. While some Viking settlements were short-lived, others succeeded in establishing permanent colonization, notably in the Faroe Islands, Iceland and Greenland.