Victory at Mag Coba
Archived: 26 September 2026
Abstract
In 1103, Ireland remained divided between Muirchertach Ua Briain, dominant in the south, and Domnall Ua Lochlainn of Ailech. Muirchertach led a coalition from several kingdoms, including Dublin, against the Ulaid and Domnall, but divided his forces after campaigning near Armagh. On 5 August Domnall defeated the remaining coalition at Mag Coba, killing regional kings and nobles and capturing royal insignia. The victory checked southern ambitions without ending Muirchertach’s power. Later that month Ulaid killed Norway’s King Magnus Barelegs, ending his Irish expansion. Annals also note churchmen, learning, scholarship, rural life, economies, Dublin trade, local conflicts, and a rare birth.