On this day in 1014, 88-year-old High King Brian Bóruma mac Cennétig (Brian Boru, in English) defeated the Vikings, the King of Leinster, and the Dublin Norse in the Battle of Clontarf, which took place just north of Dublin. Killed in action, the circumstances surrounding his death are uncertain. Many believe that Boru died in hand-to-hand combat, though some claim he was murdered by a Viking mercenary while praying in his tent. The battle took place on Good Friday, and according to legend, his remains are buried in the north end of St. Patrick’s Cathedral in the city of Armagh. Boru was the founder of the O’Brien Dynasty.