The most significant effect of the Vikings on European society was the formation of England and Scotland as unified nations. Prior to the Viking raids, these lands consisted of many small, separate chiefdoms.
The first recorded Viking raid on British land was at the monastery of Lindisfarne in 793 C.E. The raiders are generally believed to have been from Norway. The monastery wasn't completely destroyed, but it was eventually abandoned. Monasteries were a common target during the early Viking raids. The monasteries were known to hold objects made from gold and silver, making them highly desirable targets. This focus on religious centers led to a belief that a religious reform was needed in order to stop the raids.
Place names in Scotland and England indicate that many settlements were founded or expanded by Norwegian Vikings who settled on the land. By the end of the ninth century, the local people in Scotland, known as the Picts, had largely disappeared. They were replaced by the Scots, immigrants from Ireland.
Raids began from Denmark as well. When the raiding began, the different chiefdoms in England began to work together, until all were eventually joined together under one king. Many Norwegian and Danish raiders settled permanently in the lands of Scotland and England, where they began farming and trading.
One of the hallmarks of Viking raids was the kidnapping of people who were then sold as slaves in marketplaces in the raiders' homelands. This practice eventually led to descendants of mixed heritage and culture.