The Vikings sacked monasteries on the west coast of Ireland in 795. For 40 years they repeatedly sacked the north and east coasts. Since 840, they set up permanent bases on the Irish coast. In 888, the Viking fleet entered the Liffey River in eastern Ireland, they established a base that the Irish called Longphort, which eventually became the city of Dublin. The Vikings also set up bases at Cork, Limerick, Waterford and Wexford. One of the last major battles the Vikings took part in in Ireland was the Battle of Contarf on 23.4.1014, which helped the king of the Leinster region, Máel Morda mac Murchada, but failed. Eventually they had to return to England and Scotland.
During the 10th century, Denmark became a kingdom with strong central power. The Danish King Svend Tveskæg (bearded Svend) conquered England in 1013 and laid the foundation for an empire in the North Sea of Denmark, England, Norway and part of Sweden that existed until his son Knud the Great (Knud II, Canute the Great in English, about 995-1035) succeeded from 1016 until his death, in 1035.