Editing Brian Boru (section)

== Early reign in Munster ==
Despite the death of Mathgamain, the Dál gCais remained a powerful force. Mathgamain was succeeded as King of Thomond by Brian, who quickly proved to be as fine a commander of armies as his brother was. After attacking and killing the much-weakened Ivar in the year 977, Brian pursued a new target, intending to eradicate the remaining Viking presence in Munster. Upon ascending to the throne, Imar, ruler or governor of the city of Limerick who was loyal to the now-slain Ivar, fled the city by ship down the River Shannon towards the [[Shannon Estuary|Shannon estuary]] and took refuge in a monastery on [[Inis Cathaigh]] (Scattery Island), accompanied by his sons. However, in an act of revenge for the death of his brother, Brian set aside the sacred traditions and attacked the island with his troops, slaughtered the Vikings and desecrated the church.<ref name=":6">{{Cite web|title=Brian Boru and Dynastic Upheaval|url=https://www.wesleyjohnston.com/users/ireland/past/pre_norman_history/brian_boru.html|website=wesleyjohnston|access-date=14 June 2020|archive-date=30 January 2020|archive-url=https://web.archive.org/web/20200130034430/http://www.wesleyjohnston.com/users/ireland/past/pre_norman_history/brian_boru.html|url-status=live}}</ref>

Around the same time, in 978, Brian challenged Máel Muad to battle, and defeated him in the fateful [[Battle of Belach Lechta]]. Máel Muad was killed in the battle and afterwards the Eóganachta were no longer viable for the provincial Kingship, which was based upon lineage. Therefore, the Kingship of Munster passed to the Dál gCais, and Brian became king.{{citation needed|date=August 2020}}

Afterwards, the last opposition remaining in Munster was an alliance consisting of the rebellious Irish led by Donnubán (Donovan), the man responsible for Mathgamain's death, and the remaining Norse/Viking forces, possibly led by Ivar's last remaining son and designated successor, Aralt (Harold). Brian attacked them at the [[Battle of Cathair Cuan]], which may have been either a single battle or an extended conflict over the period 977–978. In any case, the event is mentioned in the Annals, and the later source the ''Cogadh'' describes Brian making a "great slaughter" of his enemies, killing both Donnubán and Aralt, and securing his position within the province.<ref>{{Cite web|last=Todd|first=James Henthorn|title=Cogadh Gaédhal re Galliabh|url=https://books.google.com/books?id=TgMGAAAAQAAJ&q=island|website=Google books|year=1867|pages=103|access-date=19 September 2020|archive-date=25 September 2021|archive-url=https://web.archive.org/web/20210925142804/https://books.google.com/books?id=TgMGAAAAQAAJ&q=island|url-status=live}}</ref>

However, he did allow some of the Norse to remain in their settlement, as they were wealthy and now central to trade in the region, particularly the slave trade, and possessed a fleet of great value, which Brian would utilise in his later naval expeditions.<ref name=":3" />

[[Cian mac Máelmuaid|Cian]], the son of his brother Mathgamain's sworn enemy Máel Muad, later became a loyal ally of Brian and served under him in a number of campaigns. According to some accounts, Cian would later marry one of Brian's daughters, Sadbh (died 1048).{{citation needed|date=August 2020}}