<P> In 865 a group of hitherto uncoordinated bands of predominantly Danish Vikings joined together to form a large army and landed in East Anglia . The Anglo - Saxon Chronicle described this force as the Great Heathen Army and went onto say that it was led by Ivar the Boneless and Halfdan . The army crossed the Midlands into Northumbria and captured York (Jorvik). In 871 the Great Heathen army was reinforced by what was known as the Great Summer Army, one of its leaders was Guthrum . In 875 the Great Heathen Army split into two bands, with Guthrum leading one back to Wessex, and Hafdan taking his followers north . Then in 876, Halfdan shared out Northumbrian land amongst his men, who "ploughed the land and supported themselves"; this land was part of what became known as the Danelaw . Most of the English kingdoms, being in turmoil, could not stand against the Vikings, but King Alfred of Wessex defeated Guthrum's army at the Battle of Edington in 878 . There followed the Treaty of Wedmore the same year and the Treaty of Alfred and Guthrum in 886 . These treaties formalised the boundaries of the English kingdoms and the Viking Danelaw territory, with provisions for peaceful relations between the English and the Vikings . Despite these treaties, conflict continued on and off . However, Alfred and his successors eventually drove back the Viking frontier and retook York . </P> <P> A new wave of Vikings appeared in England in 947, when Erik Bloodaxe captured York . The Viking presence continued through the reign of the Danish prince Cnut the Great (reigned as King of England: 1016--1035), after which a series of inheritance arguments weakened the hold on power of Cnut's heirs . </P> <P> When King Edward the Confessor died in 1066, the Norwegian king Harald Hardrada challenged his successor as King of England, Harold Godwinson . Hardrada was killed, and his Norwegian army defeated, by Harold Godwinson on 25 September 1066 at the Battle of Stamford Bridge . Harold Godwinson himself died when William the Conqueror defeated the English army at the Battle of Hastings in October 1066 . William was crowned king of England on 25 December 1066, however it was several years before he was able to bring the kingdom under his complete control . In 1070 the Danish king Sweyn Estridsson sailed up the Humber with an army in support of Edgar the Ætheling, the last surviving male member of the English royal family . However, after capturing York, Sweyn accepted a payment from William to desert Edgar . Five years later one of Sweyn's sons set sail for England to support another English rebellion, but it had been crushed before the expedition arrived, so they settled for plundering the city of York and the surrounding area before returning home . In 1085 Sweyn's son, now Canute IV of Denmark planned a major invasion against England but the assembled fleet never sailed . No further serious Danish invasions or raids on England occurred after this . </P> <P> Note that not all the Norse arriving in Ireland and Great Britain came as raiders . Many arrived with families and livestock, often in the wake of the capture of territory by their forces . The populations then merged over time by intermarriage into the Anglo - Saxon population of these areas . Many words in the English language come from old Scandinavian languages, showing the importance of this contact . </P>

Which region was not conquered by the vikings at some point in the middle ages