The south of Ireland (the provinces of Munster and southern Leinster) was dominated, as it had been for over two centuries, by the Old English Butlers of Ormonde and the FitzGeralds of Desmond.
This ensured FitzMaurice the support of important Munster clans, notably MacCarthy Mór, O'Sullivan Beare and O'Keefe, and two prominent Butlers, brothers of the Earl.