Vikings, also called Northmen of Norse, were Scandinavians from Denmark, Norway, and Sweden who raided coastal towns in England, Scotland, Ireland, and France. After the death of King Louis the Pious, the attacks from Vikings intensified and overwhelmed the French region of the Holy Roman Empire. The Norsemen raided towns, burned churches and farms, and killed or enslaved hundreds of civilians. The French city of Tours was pillaged seven times, in 853, 856, 862, 872, 886, 903, and 919. Over a 40 year period, Paris was besieged four times, pillaged three times, and burned twice. 

The Kings of France were too weak to provide protection to civilians, so this led to the development of feudalism. King Charles the Simple gave the Vikings Normandy, a part of Northern France, that they could rule. In the East, the Magyars terrorized the population of Germany, but posed less of a threat than the Vikings. The Magyars were eventually christianized and formed the nation of Hungary. 

Feudalism is the exchange of free labor for protection and it took hold in Europe during the 9th century after the Viking, Magyar, and Muslim invasions. Civilians worked for dukes, earls, and kings in exchange for safety. A lord kept his own part of the realm and dispensed justice, collected taxes, maintained infrastructure, and protected the poor, orphans, and widows. Vassals were given large land grants to provide smaller land grants for peasants. They were also the protectors of the realm and chose knights as physical protectors of the people. 

In the British Isles, the Anglo-Saxons became the most powerful tribe and subjugated most of England, which was made up of seven kingdoms: Kent, Essex, Sussex, Wessex, Northumbria, East Anglia, and Mercia. In the late 8th century, Viking invasions devastated the British Isles. Alfred the Great (ruled 871-899) was the king of Wessex and defeated the Vikings after building a navy and also helped translate classical Latin works into the Anglo-Saxon language. Some of the Danish Vikings stayed in England after the war, became Christianized, and married Anglo-Saxons. 

From the mid-900s to 980, England was relatively peaceful, until Vikings invaded again, and a Danish Norseman named Canute became England’s ruler. Norman-raised Saint Edward the Confessor ruled England from 1042 to 1066. After Edward’s death, Harold, the Earl of Wessex and William of Normandy both claimed the crown. William of Normandy invaded England and defeated Harold at the Battle of Hastings, making him the new king. William, now known as William the Conqueror, gave large tracts of English land to French nobles from Normandy. William and his successors governed England as a part of France, but the Normans lost these holdings by 1204.