Editing Brian Boru (section)

== Reign of Mathgamain ==
In 964, Brian's older brother, [[Mathgamain mac Cennétig|Mathgamain]], claimed control over the entire province of Munster by capturing the [[Rock of Cashel]], capital of the ancient [[Eóganachta]], the hereditary overlords or High Kings of Munster, but who in dynastic strife and with multiple assassinations had weakened themselves to the point they were now impotent. Earlier attacks from both the [[Uí Néill]] and Vikings were also factors. This situation allowed the illegitimate (from the Eóganacht perspective) but militarized Dál Cais to attempt to seize the provincial kingship. Mathgamain was never fully recognized and was opposed throughout his career in the 960s and 970s by [[Máel Muad mac Brain]], a semi-outsider from the Cashel perspective but still a legitimate Eóganacht claimant from far south Munster.

In addition to Máel Muad, the Norse king [[Ivar of Limerick]] was a threat and may have been attempting to establish some overlordship in the province or a region of it himself, with the ''[[Cogad Gaedel re Gallaib]]'' even asserting he actually achieved this until routed by Mathgamain and Brian in the celebrated [[Battle of Sulcoit]] in 968.

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 [[Guerrilla warfare|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.<ref name="Clare"/>

They gathered an army of kings from all over Munster, including their former enemy Maél Muad. They ambushed and routed the Norse at the Battle of Sulcoit. They followed up their victory by [[Burning of Luimnech|looting and burning Limerick]]. They killed every man of fighting age and [[Slavery|enslaved]] the rest of the population.

This was the first of three battles which highlighted Brian's career. This victory was not decisive and eventually there grew up a brief alliance of sorts between Mathgamain, Máel Muad and others to drive the Norse "soldiers" or "officials" out of Munster and destroy their Limerick fortress in 972.<ref>[[Annals of Inisfallen]], 972</ref> The two Gaelic claimants were soon back to fighting and the fortuitous capture of Mathgamain in 976 by [[Donnubán mac Cathail]] allowed him to be effortlessly dispatched or murdered by Máel Muad, who would now rule as king of Cashel for two years.