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.
Auisle
The earliest recorded Viking raids in Ireland occurred in 795. Over time, these raids increased in intensity, and they overwintered in Ireland for the first time in 840–841. Later in 841 a longphort was constructed at Áth Cliath (Irish for "hurdled ford"), a site which would later develop into the city of Dublin. Longphorts were also established at other sites around Ireland, some of which developed into larger Viking settlements over time. The Viking population in Ireland was boosted in 851 with the arrival of a large group known as "dark foreigners" – a contentious term usually considered to mean the newly arrived Vikings, as opposed to the "fair foreigners", i.e. the Viking population which was resident in arrival prior to this influx. A kingdom in Viking Scotland was established by the mid ninth-century, and it exerted control over some of the Vikings in Ireland. By 853 a separate kingdom of Dublin had been set up which claimed control over all the Vikings in Ireland.