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.
Viking raids in the Rhineland
During this time, the Vikings attacked the Frankish Empire sailing their ships up the big rivers from the North Sea and Atlantic Ocean. Such raids mainly affected areas on the Seine and in modern-day Netherlands and Belgium. Previously, the Vikings had raided England (Lindisfarne, 793) and Ireland (Dublin, 795). In 820, the first major attack by Vikings on the Frankish Empire was recorded, taking place around the mouth of the river Seine, and at the same time other Vikings probably invaded Flanders. In 845, Paris was attacked for the first time with about 700 longships up the Seine. The Parisians bought the raiders off with 7,000 pounds of silver. By 926, thirteen of these payments have been documented in the Frankish Empire. The Elbe estuary and the already fortified city of Hamburg were attacked by Danish warriors in 845.