The Five Great Fifths of Ireland are a living fact in the political framework of the stories of the Ulster Cycle. Surely then it is in those stories themselves and in the antiquity of their tradition that we must seek the evidence about these divisions, their location and extent, and not in the unreconciled statements of writers in a later age. The teaching of the Ulster stories on this matter is clear and unmistakable. It is the same throughout all of them and will be found summarised in a few sentences of the story of the Battle of Rosnaree. First we are told how this battle was caused. In the great expedition of Táin Bó Cuailnge, four of the Great Fifths had joined together for the invasion of Ulster. The invasion was not a military success, but it had secured its object, the carrying away of the Brown Bull in spite of the Ulster king, and Ulster had suffered from the ravages of war. Conchobhar, following up the retreating army of Connacht, had overtaken and defeated it on the banks of the Shannon, but he had not recovered the Brown Bull, and the other three Fifths of Ireland had got away without making any reparation for the great raid. And Conchobhar vowed that he would exact reparation or inflict punishment. He called the forces of Ulster together. These things were speedily reported to the other four Fifths of Ireland, and without delay the king of each Fifth prepared for resistance and summoned his forces to meet him at his royal seat. Here follows a recitation of the names of the four kings and their four capital places in which their armies were mustered. The king of Tara, Cairbre Nia Fear, called out the Luaighni of Tara to meet him at Tara. It is to be remembered that in these stories Tara is not the royal seat of kings of all Ireland. There are no kings of all Ireland. The Galians of Leinster are summoned to meet their king, Fionn File, at Dinn Riogh on the banks of the Barrow. The Clanna Deadhadh, which is another name for the Iverni or Érainn of Munster, are summoned to meet their king, Eochaidh MacLuchta, at his royal seat of Teamhair Érann. The muster of Connacht is held by Ailill and Meadhbh at Cruachain. In this account of the five musters, there is no room for misconception. The author of the story was not in the slightest doubt as to the identity of the Five Fifths. His account is in complete harmony with the whole tenour of the stories relative to that age. In it, there is one Fifth of Munster, and all possibility of another is precluded. There is one Fifth of Connacht and one Fifth of Ulster. How are the two remaining Fifths constituted?