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 Age in Estonia
The Viking Age in Estonia was a period in the history of Estonia, part of the Viking Age (793–1066 AD). It was not a unified country at the time, and the area of Ancient Estonia was divided among loosely allied regions. It was preceded by the Bronze and Early Iron Ages in Estonia, during which an agrarian society had developed, the Migration Period (450–550 AD), and Pre-Viking Age (550–800 AD) with the Viking Age itself lasting between 800–1050 AD. It is often considered to be part of the Iron Age period which started around 400 AD and ended around 1200 AD, soon after Estonian Vikings were recorded in the "Eric Chronicles" to have sacked Sigtuna in 1187.