The Viking invasions
The name of Viking - pirate or sea-raider - was derived from "wic" - the temporary camps established by the marauders. The Vikings originated in Denmark and Norway, and the British Isles were not their only target. Vikings were skilled soldiers and sailors who sent expeditions to, and established settlements in, Russia, Greenland, Iceland, America, France, and Spain - as well as England.
The earliest recorded Viking raid on England was in 789, soon followed by another in 793-4. Both of these aimed at plundering Northumbrian monasteries. From the 830 to 860, the Vikings attacked almost every year and from almost every point of the compass. From 865 the Norse attitude towards the British Isles changed, as they began to see it as a place for potential colonisation rather than simply a place to raid. As a result of this, larger armies began arriving on Britain's shores, with the intention of conquering land and constructing settlements there.
In 866, Norse armies captured York, one of the two major cities in Anglo-Saxon England. In 871, King Æthelred of Wessex, who had been leading the conflict against the Vikings, died, and was succeeded to the throne by his younger brother, Alfred the Great. Meanwhile, many Anglo-Saxon kings began to capitulate to the Viking demands, and handed over land to the invading Norse settlers. In 876, the Northumbrian monarch Healfdene gave up his lands to them, and in the next four years they gained further land in the kingdoms of Mercia and East Anglia as well. King Alfred continued his conflict with the invading forces, but was driven back into Somerset in the south-west of his kingdom in 878, where he was forced to take refuge in the marshes of Athelney.
Alfred regrouped his military forces and defeated the armies of the Norse monarch of East Anglia, Guthrum, at the Battle of Edington. Following Guthrum's defeat, in 886 the Treaty of Wedmore was signed between the (Norse-controlled) East Anglian and Wessex governments that established a boundary between the two kingdoms. The area to the north and east of this boundary became known as the Danelaw because it was under the control of Norse political influence, whilst those areas south and west of it remained under Anglo-Saxon dominance. Alfred's government set about constructing a series of defended towns or burhs, began the construction of a navy and organised a militia system whereby half of his peasant army remained on active service. Although there were continuous attacks on Wessex by new Viking armies, the kingdom's new defences proved a success and in 896 the invaders dispersed, instead settling in East Anglia and Northumbria, with some instead sailing to Normandy.
In 1016, Cnut (or Canute) became king of England, and after further campaigns in Scandinavia he could claim in 1027 to be 'king of the whole of England and Denmark and Norway and of parts of Sweden'. Cnut was a strong and effective king. He introduced some Danish customs to England, but England also influenced Denmark. For instance, Cnut appointed several Englishmen as bishops in Denmark, and even today most of the ordinary Danish words of church organisation are English in origin.
In an attempt at reconciliation with the English he had conquered, Cnut married Emma, the widow of Æthelred. She was the daughter of the duke of Normandy, himself the descendant of Vikings or Northmen (Normans). She bore Cnut a son, Harthacnut, but she had also had a son by Æthelred, who succeeded Harthacnut as Edward II, the Confessor (1042 - 1066).
When Edward died without children, it was natural that Emma's great-nephew, Duke William, should lay claim to the throne. It was just as natural that this claim should be resisted by Harold, the son of Godwin, Edward's most powerful noble.
Harold II successfully beat off the invasion by Harald Hardrada of Norway, defeating him at Stamford Bridge near York in September 1066. Even when he and his troops arrived, exhausted, at Hastings three weeks later to face William's Norman invaders, he nearly prevailed.
But William won, and the last English royal dynasty perished.