Miles O'Brien, who claimed to be a descendant of Boru, created an holoprogram of the battle and enjoyed reliving the battle in Deep Space 9's holosuites. (DS9: "Bar Association", "It's Only a Paper Moon")
The Battle of Clontarf took place in 1014. Brian Boru the King of Munster led his army against Máelmorda Mac Murchada the King of Leinster. Máelmorda's cousin Sigtrygg who was a Viking, also united his Viking army who were mainly from the Orkney Islands with Leinster. Brian Boru's forces eventually won the battle, but Boru himself was killed by retreating Vikings who stumbled upon his tent. The victory was not without its consequences for Boru's forces. As well as Boru himself being killed his army was severely depleted during the battle. Furthermore the army was repeatedly attacked on its way back to Munster, by other Kings who saw their chance to seize power. It is often said that the defeat of the Vikings in the Battle of Clontarf ended Viking rule in Ireland. But this is very inaccurate, as the Vikings by this time had been well integrated into Irish society and they had allied themselves with many Irish clans, like they did with Máelmorda Mac Murchada.