The Fitzgerald Earls of Kildare and the Butler Earls of Ormond were the foremost old colonial magnates in the late medieval Lordship of Ireland. Rivals for power and influence throughout the island but in particular for the post of chief governor, the principal representative of the English crown in Ireland, their struggle for mastery expressed itself in multiple ways ranging from competition for cultural hegemony to outright military confrontation. This book, based on extensive original research including hitherto unexplored evidence from literary sources and material culture, serves to counterbalance the anti-Kildare impression given by official documents such as the State Papers, which stressed that the objective of a military conquest of Gaelic Ireland was paramount. Instead, the book argues that the Kildare-Ormond rivalry was a more subtle and sophisticated conflict between two different concepts of what Ireland should be, the frequently dominant Fitzgeralds promoting the idea of Ireland as an integrated polity with the recognition and co-option of leading figures in Gaelic Ireland, the opposing Butlers embodying the traditional Cambro-Norman ideas of conquest. However, it is further argued that these opposing positions were not fundamental but conditional, dependent upon which great house held the chief governorship. The book elaborates on these alternating concepts of Ireland, showing how the political war between the two magnate families, and the accompanying culture war, played out over time.