Military history of Ireland
The Vikings pillaged monasteries on Ireland's west coast in 795, and then spread out to cover the rest of the coastline. The north and east of the island were most affected. During the first 40 years, the raids were conducted by small, mobile Viking groups. From 830 on, the groups consisted of large fleets of Viking ships. From 840, the Vikings began establishing permanent bases at the coasts. Dublin was the most significant settlement in the long term. The Irish became accustomed to the Viking presence and culture and in many cases became allies, with intermarriage common throughout Ireland. A major Irish battle involving Vikings was fought at the Battle of Clontarf in 1014, in which a large force of Vikings and their Irish allies were defeated by the gathered Irish forces of Brian Boru, then the High King of Ireland along with a small contingent of Viking defectors. After this date Viking activity was sporadic with various Kings and nobles attempting to extend their power base. In 1099, Magnus Barefoot, the King of Norway, and his Viking army had successfully campaigned alongside their Irish allies against opposing Irish warbands. On his return his force was ambushed and killed on the north coast of Ireland.
Vikings
Geographically, a Viking Age may be assigned to not only Scandinavian lands (modern Denmark, Norway and Sweden), but also territories under North Germanic dominance, mainly the Danelaw, including Scandinavian York, the administrative centre of the remains of the Kingdom of Northumbria, parts of Mercia, and East Anglia. Viking navigators opened the road to new lands to the north, west and east, resulting in the foundation of independent settlements in the Shetland, Orkney, and Faroe Islands; Iceland; Greenland; and L'Anse aux Meadows, a short-lived settlement in Newfoundland, circa 1000. The Greenland settlement was established around 980, during the Medieval Warm Period, and its demise by the mid-15th century may have been partly due to climate change. The Viking Rurik dynasty took control of territories in Slavic and Finno-Ugric-dominated areas of Eastern Europe; they annexed Kiev in 882 to serve as the capital of the Kievan Rus'.