By 1014 the redoubtable warlord Brian Boru claimed the position of ‘High King of all Ireland’. He seems to have been planning to bring his realm into line with a more centralised European model. Unfortunately for him he’d only just got started on this when the Leinstermen revolted against his rule in league with the Hiberno-Norse of Dublin. The latter drew in opportunistic ‘allies’ in the form of Sigurd of Orkney and Brodir of Man, who turned up ‘uninvited’ with large retinues of Vikings and a high kingship agenda of their own.
Brian for his part called up his Irish followers, mostly from the west and south-west, but also a large force of Hiberno-Norse from the cities of Limerick and Waterford. He had coerced support from the King of Meath, a subjugated rival for the high kingship. The latter held his force in position during the battle until its outcome was decided, and only joined in the final slaughter.