[3] The Danelaw originated in the conquest and occupation of large parts of eastern and northern England by Danish Vikings in the late ninth century.

[4] The Danelaw originated from the invasion of the Great Heathen Army into England in 865, but the term was not used to describe a geographic area until the 11th century.

With the increase in population and productivity in Scandinavia, Viking warriors, having sought treasure and glory in the nearby British Isles, "proceeded to plough and support themselves", in the words of the Anglo-Saxon Chronicle for 876.

In 886, the Treaty of Alfred and Guthrum was formalised, defining the boundaries of their kingdoms, with provisions for peaceful relations between the English and the Vikings.

[6] The Danelaw roughly comprised these contemporary 16 ceremonial counties and shires: Greater London, Leicester, York, Nottingham, Derby, Lincoln, Essex, Cambridge, Suffolk, Norfolk, Northampton, Huntingdon, Bedford, Hertford, Middlesex, and Buckingham.

In 865, instead of raiding, the Danes landed a large army in East Anglia, with the intention of conquering the four Anglo-Saxon kingdoms of England.

[11] After making peace with the local East Anglian king in return for horses,[citation needed] the Great Heathen Army moved north.

In ten years, the Danes had gained control over East Anglia, Northumbria and Mercia, leaving just Wessex resisting.

The reasons for the waves of immigration were complex and bound to the political situation in Scandinavia at that time; they occurred when Viking settlers were also establishing their presence in the Hebrides, Isle of Man, Orkney, Shetland, Faroe Islands, Ireland, Iceland, Greenland, L'Anse aux Meadows, France (Normandy), the Baltics, Russia and Ukraine (see Kievan Rus').

Then, three weeks later, William of Normandy defeated Harold at the Battle of Hastings, in Sussex, and in December he accepted the submission of Edgar the Ætheling, last in the line of Anglo-Saxon royal succession, at Berkhamsted.

The Danelaw appeared in legislation as late as the early 12th century with the Leges Henrici Primi, where it is referred to as one of the laws together with those of Wessex and Mercia into which England was divided.

Led by the brothers Halfdan and Ivar the Boneless, they wintered in East Anglia, where they demanded and received tribute in exchange for a temporary peace.

In response, King Æthelred of Wessex, along with his brother Alfred, marched against the Danes, who were positioned behind fortifications in Nottingham, but were unable to draw them into battle.

King Burgred of Mercia fought in vain against Ivar the Boneless and his Danish invaders for three years until 874, when he fled to Europe.

However, they stopped during their march to capture a small fortress at Countisbury Hill, held by a Wessex ealdorman named Odda.

The Saxons, led by Odda, attacked the Danes while they slept and defeated their superior forces, saving Alfred from being trapped between the two armies.

They ravaged Mercia before winning a pyrrhic victory that saw the death of Æthelwald and the Danish King Eohric; this allowed Edward the Elder to consolidate power.

917 − In return for peace and protection, the Kingdoms of Essex and East Anglia accepted Edward the Elder as their suzerain overlord.

954 − King Eric was driven out of Northumbria, his death marking the end of the prospect of a Northern Viking Kingdom stretching from York to Dublin and the Isles.

1002 – St. Brice's Day massacre of the Danes 1066 − Harald Hardrada landed with an army, hoping to take control of York and the English crown.

1075 − One of Sweyn's sons, Knut, set sail for England to support an English rebellion, but it had been crushed before he arrived, so he settled for plundering the city of York and surrounding area, before returning home.

Informed of his planned crossing, William hurries back to England with a northern French army, and the Danish expedition is called off.

[citation needed] Five fortified towns became particularly important in the Danelaw: Leicester, Nottingham, Derby, Stamford and Lincoln, broadly delineating the area now called the East Midlands.

Many of the legalistic concepts were compatible; for example, the Viking wapentake, the standard for land division in the Danelaw, was effectively interchangeable with the hundred.

"[30] The influence of this period of Scandinavian settlement can still be seen in the North of England and the East Midlands, and is particularly evident in place-names, endings such as -howe, -by (meaning "village") or -thorp ("hamlet") having Old Norse origins.

In 2000, the BBC commissioned a genetic survey of the British Isles by a team from University College London led by Professor David Goldstein for its programme 'Blood of the Vikings'.

It concluded that Norse (Norwegian) invaders settled sporadically throughout the British Isles with a particular concentration in certain areas, such as Orkney and Shetland.

That was decided on the basis that the latter two groups originated from areas that overlap each other on the continental North Sea coast (ranging from the Jutland Peninsula to Belgium) and were therefore considered too difficult to genetically distinguish.

[38] A 10-year genetic study published in 2020 found evidence of a major influx of Danish settlers into England during the Viking period.

Experts think the rediscovered site, which lies amidst the old oaks of an area known as the Birklands in Sherwood Forest, may also yield clues as to the boundary of the ancient Anglo Saxon kingdoms of Mercia and Northumbria.