The Battle of Knockdoe, a battle between the forces of two Anglo-Irish lords — Gerald FitzGerald, Earl of Kildare, the Lord Deputy of Ireland, and Ulick Fionn Burke, lord of Clanricarde, takes place on August 19, 1504 at Knockdoe, County Galway.
Gerald FitzGerald becomes concerned that Ulick Burke’s attempt to gain supremacy in Connacht could simultaneously threaten the Crown’s interests in that province and his claim to be the paramount magnate in Ireland. He tries to persuade Ulick to acknowledge his authority by giving him his daughter Estacia in marriage. Ulick Burke, however, resists all attempts to have his power subordinated by the Earl of Kildare, forming an alliance with O’Brien of Thomond and the magnates of Munster. The Burkes of Mayo, on the other hand, join forces with Kildare with the aim of suppressing their dangerous neighbour.
For political and possibly for personal reasons, the Lord Deputy is eager to help O’Kelly weaken the prestige of Clanrickarde. Both sides gather a large contingent of lesser magnates and their armies. The Lord Deputy’s forces include contingents from Leinster, Ulster, and Connacht, among which are the armies of Red Hugh O’Donnell and Art Óg Ó Néill, the McDermotts and Morrisroes of Connacht, and a contingent provided by O’Kelly. Facing them are the forces of Burke and his allies – the O’Briens of Thomond, the McNamaras, the O’Kennedys, and the O’Carrolls.
The armies meet on the slopes of Knockdoe, almost a mile to the north of Lackagh Parish Church, with heavily armed Gallowglass playing a large part on both sides. It is said that firearms are employed in the course of the battle, an early instance of their use in Ireland. The battle apparently lasts all day, with the heaviest fighting taking place along the River Clare in the townland of Ballybrone. The precise number of casualties is unknown, though contemporary observers are impressed by the extent of the slaughter. Around the summit of Knockdoe are many cairns where the dead are said to have been buried, with one in particular being pointed out as the resting place of the two sons of O’Brien of Thomond.
The Lord Deputy, though victorious, has many among the slain. His army remains the night on the field as a token of victory, then marches to Galway, looting Claregalway castle en route and taking as prisoners the two sons and daughter of Ulick Burke. They remain in Galway for a few days and then travel to Athenry.
The Clanrickarde Burkes fade into obscurity for some decades, with their rivals, the Mayo Burkes, gaining influence as a consequence.