Initially, Mathgamain had made peace with the Norse of Limerick. However, Brian was eager to avenge the deaths of his family members at the hands of the Vikings, and deserted with a band of his followers and launched a guerilla campaign against the Vikings from the mountains of Munster. They attacked Viking forts and patrols and survived with whatever food and weapons they found. Their attacks were successful in weakening the Vikings, but casualties began to mount and according to writings by Brian's scribe, just 15 men remained. However, at this point Mathgamain, inspired by the courage of his younger brother, decided to attack the Vikings with Brian and drive them from Limerick and Munster once and for all.
initially mathgamain had made peace with the norse of limerick however brian was eager to avenge the deaths of his family members at the hands of the vikings and deserted with a band of his followers and launched a guerilla campaign against the vikings from the mountains of munster they attacked viking forts and patrols and survived with whatever food and weapons they found their attacks were successful in weakening the vikings but casualties began to mount and according to writings by brian's scribe just 15 men remained however at this point mathgamain inspired by the courage of his younger brother decided to attack the vikings with brian and drive them from limerick and munster once and for all