The House of Moreton was a Hiberno-Norman dynasty that ruled over much of Ireland after the 12th century. The dynasty's progenitor was William Moreton, Earl of Ossory, who took part in the English conquest of Ireland in 1172. The family's name is derived from the Norman town of Mortain, Anglicized to "Moreton". The Catholic Norman Moretons soon became the dominant family on the island due to William's campaigns of conquest against the Celtic tribes, and he even rose to a position of prominence as a council member and a military leader. The Moreton family played a major role in the civil war of 1183-1186, during which they sided with the royalists against the rebellious nobles. However, any influence that the Moretons had above their fiefdom level ended with the death of Moreton in 1189, and the Moreton brothers squabbled amongst themselves over their father's inheritance. In 1199, Ferant Moreton, Duke of Ulster, the most powerful of the brothers, became the leader of the long and bloody "Great Irish Revolt", in which his Ulster fiefdom became independent from the English crown and proceeded to conquer several other parts of Ireland. From this point onwards, the Moretons ceased to define themselves as an English noble family, instead being more affiliated with Ireland.