Brian Boru, High King of Ireland
Brian Boru or Brian Boroimhe (940?–1014), clan prince, succeeded his brother Mathghamhain, who had seized the throne of Munster from the Eogharacht rulers (963). The Battle of Bealach Leachta, in 978, marked the first major defeat of the Danes in Ireland and established Brian Boru as a serious contender for position of Ard Rí (High King) of Ireland.
Brian subjugated all Munster, then extended his power over all S Ireland, and in 1002 became high king of Ireland by right of conquest.
The battle was the climax of a power-struggle between the Dál gCais of North Munster and the Lords of Carbery. Mahon of the Dál gCais was captured by Imar, a Limerick Dane who was allied to the O'Donovans and O'Mahonys of Carbery. Imar delivered Mahon, a brother of Brian Boru of Kincora, into the hands of Maolmuidh of the O'Mahonys, who killed him at Aghabullogue.
Brian Boru came seeking revenge, first despatching Imar the Dane, then picking off O'Donovan, and then meeting the O'Mahonys at Bealach Leachta. A fierce battle was waged all day on the riverside plain. Brian's army had swelled as many minor chieftains began to recognise his potential, and Maolmuidh had the support of the remains of the O'Donovan clan and 1500 Danes.
Maolmuidh and his troops were forced back, and Maolmuidh took refuge at Leacha Dubh (present site of Macroom Golf Course), where he was found and killed. Fulfilling a curse put on him for the assassination of Mahon, Maolmuidh is buried on the north side of the hill, where the sun never shines, under a harsh wind. Three standing stones were erected on the site of the battle (of which two remain). One is known as Leacht Mahon.
Following the battle Brian Boru was crowned King of Munster. Brian took over all Munster, then extended his power over all Southern Ireland, and in 1002 became high king of Ireland by right of conquest.
As his power increased, relations with the Norse rulers on the Irish coast grew steadily worse. Sitric, king of the Dublin Norse, formed a coalition of the Norse of Ireland, the Hebrides, the Orkneys, and Iceland as well as Brian's Irish enemies against Brian. On Good Friday (Apr. 23), 1014, Brian's forces met and annihilated the allies at Clontarf, near Dublin. Soon afterward he was murdered in his tent. Brian's victory broke the Norse power in Ireland forever, but Ireland fell into anarchy.