According to legend, the island of Ireland was invaded six different times in its prehistory. The story of these invasions is told in a body of myth called the Mythological Cycle, much of which was recorded in the twelfth century in the Book of Invasions. The ultimate consequence of all these invasions was a final battle between two groups of supernatural people, the Tuatha Dé Danaan and the Fomorians, and the establishment of civilization and social order.
Invasions by Descendants of Noah
The first invasion was led by one of the granddaughters of Noah (the Biblical Noah who built the Ark), but her timing was bad; all of her people drowned in the great flood. Three hundred years later, another descendant of Noah, Parthalón, settled Ireland, building houses and clearing fields for farming. Parthalón's sworn enemies were the Fomorians, one-armed, one-legged monsters descended from Noah's cursed son, Ham.
Parthalón and his people all died of plague. Thirty years later, the third invasion arrived, led by a man named Nemhedh. They attacked the Fomorians, but most of them died in the effort. A few survivors fled to Greece, where they became slaves; they were called the Fir Bolg.
The Fir Bolg came back to Ireland, which they divided into the five provinces of the Celts. They established a kingship and ruled the land for thirty-seven years. Their last king, Eochaidh mac Eirc, was a perfect, just ruler; during his reign no rain fell, only dew; there was no year without a harvest; and nobody told any falsehoods.
The First Battle of Magh Tuiredh
The Fir Bolg had a nice arrangement, but it was too good to last. Yet another group of people decided to invade Ireland: the Tuatha Dé Danaan.
The Tuatha Dé Danaan were the people of the mother goddess Anu. According to Irish legend, they arrived around 350 B.C.E. They came from four cities in ancient Greece, which is where they learned about prophecy and magic, the secrets of the druids. They brought with them four treasures:
The cauldron of the Daghdha — this vessel was always full of food.
The spear of Lug — this weapon ensured victory to its holder.
The sword of Nuadhu Airgedlámh — no enemy could escape from it once it was drawn from its sheath.
The Lia Fáil — known as the “Stone of Destiny,” it shrieked when the feet of a lawful king rested on it; this ended up on Tara Hill, seat of Irish kings.
The Tuatha Dé Danaan were skilled in magic and fighting. Their leader, Nuadhu Airgedlámh, brought them into battle. But a Fir Bolg warrior named Sreng cut his arm off at the shoulder. Sreng made peace with the Tuatha Dé Danaan and agreed to leave them all of Ireland except for Connacht (or Connaught), where he led his own people.
Poor Nuadhu Airgedlámh couldn't be king anymore, because no one with a physical defect (such as a missing arm) could be king. A man named Bres got to be king instead. Bres was the son of the Fomorian king Delbáeth; he had been adopted and raised by the Tuatha Dé Danaan, and they obviously thought they could trust him. But there they were mistaken.
Fostering was a common practice in ancient warlike states. Kings and chieftains would send their children to be raised at the courts of other rulers. This broadened the educations and connections of their children. It also provided the rulers with ready-made hostages should their allies consider becoming their enemies.
The Second Battle of Magh Tuiredh
Bres, the Fomorian, ruled the Tuatha Dé Danaan for seven years. This was a lousy time for the Tuatha Dé Danaan. The Fomorians demanded a tribute of cattle, and the gods were reduced to menial labor; even the Daghdha himself was forced to dig ditches and build a fortress for Bres.
Meanwhile, the Tuatha Dé Danaan were planning their recovery. Dian Cécht, the “Divine Physician,” made a new arm for Nuadhu out of silver, which would allow him to be king again. After a poet named Cairbre mac Étain (son of Étain) sang a verse mocking Bres, he gave up the kingship and went off to gather an army of his Fomorians. Nuadhu was reinstated as king; he and the Daghdha and Lug got together to decide how to get back at the Fomorians. (Lug had recently appeared at the court, and he had impressed everyone so much with his skill in all arts, creative and warlike, that they let him be one of their leaders.)
The Daghdha went to see Mórrígan at the festival of Samhain. She was standing astride the River Unius washing herself. They made love standing over the water, which gave that spot the name “Bed of the Couple.” She told the Daghdha that the Fomorians were coming to attack the Tuatha Dé Danaan and that he should bring his soldiers to her. She killed the son of the Fomorian king and gave two handfuls of the blood to the Tuatha Dé Danaan before they went into battle. She and her sisters Babd and Macha went to the Mound of the Hostages at Tara and made the sky rain blood down onto the battle.
Magh Tuiredh is a real place in County Sligo. Its name means “Plain of Reckoning” or “Plain of Weeping.” Some historians believe that at least one of the battles there was a real historical fight between the men of Ulster (the Tuatha Dé Danaan) and the men of Connacht (the Fir Bolg).
Lug led the Tuatha Dé Danaan in the second battle of Magh Tuiredh. The Mórrígan entered the fray, cheering on the Tuatha Dé Danaan and pursuing any Fomorians who tried to run away. Blood ran freely over the white-skinned warriors and the River Unius was clogged with corpses. Lug and his armies finally defeated the Fomorians and drove them to the sea.
After the fighting was over, Lug spared Bres in return for some information about agricultural techniques. The Mórrígan finished off the story by declaring victory for the Tuatha Dé Danaan and predicting the end of the world.
Invasion by the Milesians
The conquests of Ireland didn't stop with the Tuatha Dé Danaan. They were themselves invaded by the Milesians, the sons of Míl, also known as the Gaels.
Míl came from Galicia in northwest Spain. His full name was Miles Hispaniae (Latin for “soldier of Spain”). His wife was named Scota (“Irishwoman”). A druid named Caichér had predicted that Míl's descendants would rule Ireland, and they did.
Míl himself didn't go to Ireland, but his sons did. The Milesians arrived in Ireland sometime after the Tuatha Dé Danaan had established themselves, perhaps between 350 and 250 B.C.E. They landed in southwest Ireland during the Feast of Beltane and fought a huge battle with the Tuatha Dé Danaan. They proceeded to Tara and clinched their hold on the country.
After the battle, a poet named Amhairghin divided Ireland between the two parties. The Milesians got the part that was aboveground, and the Tuatha Dé Danaan got the underground. The defeated Tuatha Dé Danaan retreated to the hills and mounds to become the fairy people.
Some scholars think that in the original myths, the Tuatha Dé Danaan were divine, not the supernatural beings they appear to be. According to this theory, medieval monks who recorded the stories demoted the Tuatha Dé Danaan to their current stature, not wanting to suggest that any other gods could rival the Christian one.