Battle of Glenmama
1000 CE.
Shown on the map at 53.280°, -6.525°.
The Battle of Glenn Máma or Glenmama (Irish: Cath Ghleann Máma, The Battle of "The Glen of the Gap") took place most probably near Lyons Hill in Ardclough, County Kildare, Ireland, in AD 999 between Windmill Hill and Blackchurch. It was the decisive and only engagement of the brief Leinster revolt of 999–1000 against the King of Munster, Brian Boru. In it, the combined forces of the Kingdoms of Munster and Meath, under King Brian Boru and the High King of Ireland, Máel Sechnaill II, inflicted a crushing defeat on the allied armies of Leinster and Dublin, led by King Máel Mórda of Leinster. The two armies met in a narrow valley, causing a rout of Máel Mórda's army in at least three directions. They were pursued, and the main body of the army was slaughtered when they rallied at several fording points along the River Liffey. The main commanders were either killed or captured. The battle resulted in the occupation of Dublin by Brian's Munster forces, and the submission of Máel Mórda and King Sigtrygg Silkbeard of Dublin to Brian Boru. The solution did not prove permanent, however, and eventually resulted in the second Leinster revolt against Brian and the Battle of Clontarf in 1014.
Text from the Wikipedia article Battle of Glenmama, licensed CC BY-SA 4.0.