It was 1014 when the Battle of Clontarf was fought, with Brian Boru's forces against Máel Mórda mac Murchada's forces. Alongside him were Viking mercenaries from as far as the Orkney Isles, united under Sigtrygg Silkbeard.
After hours of battling, Murchada's forces were finally plunged through and routed. At the last possible moment, before Brian's forces could reach the fortress of Dublin over the bridge, Malachy II re-entered the battle.
POD vs. OTL
Brian Boru has already been slain by Brodir after the successful rout of Murchada's forces, leaving his men to fair under his remaining sons and generals.
In OTL, Malachy's forces meet Brian's at the bridge and are, just as their allies under Murchada had done before, routed to the sea this time, where Brian's forces successfully capture Dublin.
However, our POD begins with the victory of Malachy's forces. Instead, Brian's men are routed away into the sea or are killed before reaching the fortress.
In the battle, the leaders of the Orkney Isles and the Isle of Man, as well as the heirs and possible future-heirs to the kingdom have been killed. In an act of thankfulness for his help, Malachy grants Silkbeard the area north of Dublin, the Isle of Man, and the Orkney Isles.
April 23, 1014: Malachy II defeats Brian Boru's forces and takes over as High King of Eiru (Ireland).
May 12, 1014: Malachy II makes the decision to grant Sigtrygg land for helping defeat Boru.
May 13, 1014: Sigtrygg Silkbeard names his new land grant the Kingdom of Dublin. Capitols are placed in Dubh Linn on the mainland, Eday in the Orkney Isles, and Duboglassio in the Isle of Man.