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.
Sweden
During the early stages of the Scandinavian Viking Age, Ystad in the Danish province Scania and Paviken on Gotland were flourishing centres of trade, but they were not parts of the early Swedish Kingdom. Remains of what is believed to have been a large market dating from 600 to 700 AD have been found in Ystad. In Paviken, an important centre of trade in the Baltic region during the 9th and 10th century, remains have been found of a large Viking Age harbour with shipbuilding yards and handicraft industries. Between 800 and 1000, trade brought an abundance of silver to Gotland, and according to some scholars, the Gotlanders of this era hoarded more silver than the rest of the population of Scandinavia combined.