The Tuatha Dé Danann were at peace with the Fomorians. An alliance was formed between the Tuatha Dé Danann and the Fomorians, so the Fomorians had no objection to the Danann settling in Ireland. To seal the alliance, Balor gave his daughter, Ethlinn (Eithne), in marriage to the Danann Cian, the son of Dian Cecht. (There's a different version between the relationship between the Fomorians and Danann.)

The Tuatha Dé Danann arrived in a cloud of mist when the Firbolgs discovered them were in Connacht. According to Cath Maige Tuired, this mist was actually smoke from their burning ships. The Tuatha Dé Danann decided that they would not flee to their ships if they were defeated.


During this time, Eochaid Mac Eirc was king of Ireland, and the leader of the Firbolgs. Eochaid was married to Tailtiu, the Firbolg daughter of the King of the Great Plain (Mag Mor or Magmor).
The two people sent embassies to meet and talk. The two people curiously looked at one another strange clothes and weapons. The Danann spear was superbly crafted, with fine point, whereas the Firbolg spear was blunt. Bres told the Sreng, the Firbolg champion, that they wished to share the land with the Firbolgs. They exchanged weapons before returning to their people.

The Firbolgs decided that they did not want to divide and share the land with Tuatha Dé Danann. They declared war against the Dananns, when the newcomers would not leave. A battle took place in Magh Tuiredh (Moytura).

The Firbolgs lost 100,000 warriors, among those killed was Eochaid Mac Eirc, king of the Firbolgs. The Dananns also lost many people in battle as well. According to Cath Maige Tuired, Edleo Mac Allai, Ernmas, Fiacha and Tuirill Bicreo were killed. The Dananns won a convincing victory, because of their superior weapons and skills, but at the price of losing their king.

Though Nuada did not die, Nuada lost his right hand in battle. To the Danann, losing any body member would result in losing the right to become king of Ireland. Any form of physical blemish would disqualify a king from ruling. The Tuatha Dé Danann had to choose a new king; they chose Bres.

A peace treaty was drawn up, with Firbolgs receiving the province Connacht as their land, while the Danann won the rest of Ireland.