The Battle of Glenmalure (Irish: Cath Ghleann Molúra) takes place in Glenmalure, a steep U-shaped glacial valley in County Wicklow that is surrounded by forests and bogs, on August 25, 1580, during the Desmond Rebellions. A Catholic army of united Irish clans from the Wicklow Mountains led by Fiach MacHugh O’Byrne and James Eustace, 3rd Viscount Baltinglass of the Pale, defeat an English army under Arthur Grey, 14th Baron Grey de Wilton, at Clan O’Byrne‘s mountain stronghold of Glenmalure.

Grey had landed in Ireland with reinforcements from England to put down the rebellion. His strategy is to meet O’Byrne’s threat to the English heartland of Dublin and the Pale by attacking through the highlands to the south of the city. Against the advice of veteran commanders, he chooses to lead his army (around 3,000 strong) through lowland Kildare and into the Wicklow Mountains, with the aim of taking the fastness at Balinacor in the Glenmalure Valley.

While climbing the steep slopes of the valley, the inexperienced English soldiers are ambushed by the Irish who were hiding in the woods. The English are sniped at for a long period of time before their discipline collapses and they turn and flee down the valley. It is at this point that most of their casualties occur, as the Irish leave their cover and fall upon the English with swords, spears, and axes. Hundreds of English soldiers are cut down by the pursuing Irish as they try to escape the field. The remaining English have to fight a rearguard action for several miles until they reach the town of Rathdrum.

Irish sources state that around 800 English soldiers are killed, though the English put their losses at 360 dead. Among those killed is Peter Carew, cousin of his namesake colonist who had made claims to, and won, large tracts of land in southern Ireland. The remainder of the English force retreat to lowland Wicklow and from there to Dublin. However, the following year, when offered terms, most of the Irish soldiers, including O’Byrne, come in and surrender. The exception is Baltinglass, who flees to France.

The battle is commemorated in the folk song “Follow Me Up to Carlow.”

(Pictured: “Battle of Glenmalure 1580 Wicklow,” painting by Val Byrne)