The fact of the annexation of Tara and eastern Meath underlies the story of the Battle of Crinna. The cause of this battle, as stated, was the continued hostility of the Ulstermen to king Cormac's line. One king after another of this line, which, be it remembered, was the Connacht dynasty and still ruled over Connacht, had fallen in fight with the Ulster enemy. Cormac had forced Ulster to give him hostages. Such hostages were by custom honourably entertained according to their rank. The Ulster hostages sat at Cormac's own table. So unsubdued was their spirit that on one occasion they did the king the gross affront of setting fire to his beard. After this, Ulster again took up arms and drove Cormac out of Meath, forcing him to take refuge in his native realm of Connacht. There he gathered his forces and took a Munster prince, Tadhg, son of Cian, into alliance. This Tadhg figures in the genealogies as being the ancestor of a group of dynastic families which in later times ruled over certain states of Connacht, Meath and Ulster, the Luighni, Gaileanga, Cianachta, etc. These states, when we trace them back as far as possible, are native to Connacht; their branches in Meath and Ulster are frontier colonies planted to guard the conquests of the Connacht kings. Tadhg macCéin, in the story, is the personification of these colonies. Before going into battle, Tadhg made a compact with Cormac the king. They agreed that, if Tadhg came off victorious, Cormac would grant him as much territory as he could ride around in his chariot on the day of victory. In the battle of Crinna, Tadhg engaged the Ulstermen and completely defeated them. He himself was sorely wounded. He mounted his chariot and set out to ride around the territory he desired to win for himself and his descendants, and he commanded the charioteer to take such a course as to bring Tara within the circuit. Then, overcome with loss of blood from his many wounds, he fell into a swoon and lay unconscious in the chariot. King Cormac had foreseen that Tadhg would try to get possession of Tara. He desired Tara for himself, and he bribed the charioteer to leave Tara out of the circuit of the ride. At intervals during the ride, Tadhg awoke from his swoon and on each occasion he asked the charioteer "Have we brought in Tara?" and the charioteer answered "Not yet." At nightfall, Tadhg came to his senses and saw that they had reached the banks of the Liffey near Dublin. "Have we brought in Tara?" he asked again. The charioteer could not answer yes. Tadhg saw that he had been cheated, and he slew the charioteer.