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
The majority of runic inscriptions from the Viking period are found in Sweden and date from the 11th century. The oldest stone with runic inscriptions was found in Norway and dates to the 4th century, suggesting that runic inscriptions pre-date the Viking period. Many runestones in Scandinavia record the names of participants in Viking expeditions, such as the Kjula runestone that tells of extensive warfare in Western Europe and the Turinge Runestone, which tells of a war band in Eastern Europe. Other runestones mention men who died on Viking expeditions. Among them are around 25 Ingvar runestones in the Mälardalen district of Sweden, erected to commemorate members of a disastrous expedition into present-day Russia in the early 11th century. Runestones are important sources in the study of Norse society and early medieval Scandinavia, not only of the Viking segment of the population.