The history of Breifne has had a significant influence on Irelands history. MacMurrough, King of Leinster, played a role in the coming of Normans to Ireland. Bryan ORourkes aid to the survivors of the Spanish Armada, for which he was executed at Tyburn, spurred Queen Elizabeths resolve in the Tudor Conquest of Ireland, ending in the Nine Years War and the Battle of Kinsale. Plantation and the age of the landlord followed.
The kingdom of Breifne was situated in the northwest of Ireland encompassing the modern Irish counties of Leitrim and Cavan, along with parts of County Sligo. In Breifne: From Chieftain to Landlord Mary Weir traces the kingdoms dramatic history from the tenth to the twentieth to century and introduces the reader to some of the more colourful and influential characters along the way.