The Milesians were the descendants of Miled (sometimes Míl, Miletus or Milesius), a tribal king from the Iberian peninsula, the area which is now Spain and Portugal. Somewhere in the area of 1000 BC, they invaded Ireland, driving off the Tuatha de Danann and subjugating the Fir Bolg to become the ruling class of the island. They would remain so for about two millennia, until their rulership was challenged by Viking invaders in the tenth and eleventh centuries.
Much of what we know of this period in Irish folk history comes to us from the Lebor Gabála, the Book of Invasions, an early Medieval text. We are told that Miled is descended from the line of Gaedheal Glas, the original creator of the Irish language. Gaedheal dwelt with his people in Egypt, where they were friendly with the Israelites. One source tells us that Gaedheal was once bitten by a snake and then cured by Moses, who subsequently prophesied that Gaedheal's descendants would come to live in a place where there were no serpents.
Two generations later, Gaedheal's people were driven from Egypt, and they returned in ships to their original home of Scythia. There followed many disputes upon their return as to the hierarchy of power, and after a few generations of unrest, they were driven from Scythia as well. At this time they became wanderers of the sea, with no real home for several years until they landed upon the Iberian shores. They seized this land by force, and their king Breoghan had a great tower erected on a cliff overlooking the ocean. A sentinel stood watch in this tower at all times, always wary of invaders.
Years later, on a clear wintry evening, Breoghan's son Ith stood in that tower watching the sun set, and just after it sank below the horizon, he saw a distant island there, a gem of green sparkling in the light of the faded sun. Ith was the uncle of Miled, and in time he became king. While Ith ruled, Miled traveled, returning to his ancestral land of Scythia. He was welcomed by the king there, given a wife and made an army commander. He was very successful and loved by the people, so much so that the king became jealous and tried to kill him, but his wife was accidentally killed instead, and Miled avenged her by killing the king.
Miled then left Scythia, taking with him his supporters. They were so numerous that they filled sixty ships, and they journeyed to Egypt, pledging service to the king there. Miled was again made a general and wed the Pharaoh's own daughter, Scota. After some time, a messenger from Iberia arrived with news of an invasion, and Miled and his people returned home to assist Ith in battle.
The invaders were driven off, and Miled distinguished himself highly in that battle and others that followed. Seeing his nephew's popularity and influence among the people rise, Ith took Miled aside one day and revealed to him the vision of the island he had seen from the tower years before. Lately, he had heard its voice calling to him in his dreams, and the druid Caicher had prophesied that their people would settle there.
Ith named Miled to the kingship and, taking a hundred and fifty warriors with him, crossed the seas to reach Ireland. He arrived in the wake of a battle between the Tuatha de Danann and the Fomorians, in which the Danaan king had been slain. The king's three sons were preparing to divide the land and its rulership among themselves when Ith landed. They welcomed him, and seeing that he was wise and a king in his own right, asked him to divide the land among the three of them so that there could be no doubt of impartiality.
Ith did so, dividing the land fairly and equally, but finished by espousing the virtues of the fair island: "Act according to the laws of justice, for the country you dwell in is a good one. It is rich in fruit and honey, in wheat and in fish; and in heat and cold it is temperate." Hearing this, the Danaans believed that Ith coveted their land and intended to seize it, and they murdered him and threw him in the sea. But as bodies will, he washed ashore near his men's camp, and they bore his corpse home in their ships.
Miled was furious when his uncle's companions returned to Iberia, and vowed to take the three kings' land by force. He set his people to building a great navy with which they would invade Ireland. Miled was old by this time, and we are told he had at least thirty-six sons. The bulk of these were born during his early life in Iberia, before his travels. Two were born of his wife in Scythia, named Donn (sometimes Eber Donn) and Aireach, and six were his sons by Scota.
Of these, Éireamhóin (or Éremon) was the greatest warrior, and leader of his people in battle. Ír was also a fearsome fighter, but in battle a madness would come on him and in his blood-rage he would cut down friend and foe alike. Éibhear Fionn (or Eber Finn) was the most handsome and charming of them all, and he happily kept many wives (the Milesians were polygamists). Amhairghin Glúngheal (or simply, Amergin) was a bard whose consummate skill with the harp was never again achieved among men after his passing. Of the other two sons of Scota, Colptha and Érannan, little is written.
Miled did not survive to see the completion of his navy, having died of some unspecified cause in the interim. There was initially some dispute over the kingship among the sons of Miled, but this was eclipsed by the completion of the fleet of ships and preparation of the army. In the end, all of the sons of Miled left Iberia for Ireland, each with his own ship that bore his family and retainers, in addition to a complement of warriors.
As the fleet of ships approached the island, a thick mist and fog fell over them. Érannan climbed the mast of his ship to see if he could see beyond it, but a strange wind blew him down from atop it, crushing his body on the deck. The Milesian druids agreed that the Danaans were using their powers to keep them from landing. Ír rowed forth in a small boat to face them himself, but a wave crushed his boat and oars, and he drowned.
The Milesians sailed their fleet around the island, finally managing to make a landing along the western shore. Amhairghin's wife Scéine drowned during the landing, and they buried her on a hill overlooking the bay (Kenmare Bay in County Kerry), naming it Inbhear Scéine after her. Amhairghin was the first to set foot on Ireland, and when he did so he was overcome by the spirit of the land, and recited the famous and venerated Song of Amergin.
Their forces then advanced to Sliabh Mis (a mountain south of Tralee), where they encountered a Danaan queen and her retinue. Amhairghin, with his bardic gift of speech, acted as the spokesperson and diplomat for the Milesians, and the two sat and spoke. The queen, Banba, praised Amhairghin's words and ways, and asked that if his people should come into possession of Ireland, that her name be remembered as part of it. Amhairghin agreed to this, and their march continued.
A similar encounter occurred at Sliabh Éibhlinn (now Slieve Felim in County Limerick) with the lady Fódhla, and at the hill of Uisneach (Ushnagh in County Westmeath) with the lady Ériu. Amhairghin promised each that their names would be remembered as part of Ireland forever, and so it was. Of these three, only the last, Ériu, has persisted as a name for Ireland (Eire, or in its dative form, Erin), but each was used in its own time.
When the Milesians came at last to Tara, Amhairghin strode boldly into the court where the three kings were gathered, and announced that, in the name of the Milesian king Ith who they murdered, they must forfeit their rulership over Ireland or do battle to defend it. The Danaans were taken aback at this and asked for three days to gather their army. They also requested that the Milesians return to their ships and retreat nine waves from the shore during this time.
Amhairghin agreed, believing it a fair judgment to allow the Danaans time to prepare for the battle, and he and the others returned to their ships. No sooner had they cast off, however, than a mist obscured the island and a great storm raged upon their fleet. Amhairghin used the magic of his music to calm the waters again, but Donn, angered by the Danaans' dishonorable treachery, threatened to put every man, woman and child in Ireland to the sword. At this, the storm rose against his ship and drowned him and his brother Aireach.
This left only four of the named sons of Miled alive, and thirty of their ships intact. These remaining ships sailed clockwise around Ireland at Éireamhóin's command, and made their landing at the Boyne estuary. There is a mention of Colptha's death at this point, although how this happened is not made clear. As with Scéina, they buried Colptha overlooking the shore and gave the estuary the name of Inbhear Colptha.
The Milesians made camp to prepare for battle, but were then attacked by Ériu and a sizeable force. They routed the Danaans, who could not match their ferocity in battle, and Ériu fell back with her warriors to Tailtiu (now Teltown, in County Meath). The Milesians did not pursue and slaughter them, but instead took the time to bury and honor their dead before marching to Tailtiu.
When they arrived, the whole of the Danaan army had been marshaled to meet them. A vicious battle followed, in which the three kings and queens of the Danaans were all slain. Again the Danaans fled, and again the Milesians let them go, instead honoring and burying their dead. When this was done, they set out to pursue the Danaans, but could find no trace of them whatsoever. The Danaans, knowing they were outmatched physically, and ashamed of their own conduct in the face of the Milesians' unflagging honor, had fled Ireland.
The Tuatha De Danann did not flee out of Ireland, however, they fled into it, or behind it as some say. They retreated to Tir na nOg, the Land of Eternal Youth, where they would forever reside. Some of the Danaans came back to our world from time to time, sometimes tormenting, sometimes testing, other times helping or falling in love. They came to be known as the Sidhe, the Faeries, the Wee Folk, and many other names as well.
Following the Battle of Tailtiu, the sons of Miled divided the island between them. Of the named sons, only Éireamhóin, Éibhear Fionn and Amhairghin survived. Amhairghin forsook this, fearing that the division of the land would lead to divisions among them as well. His brothers did not heed him, however, and Éibhear Fionn took the southern half of Ireland to rule, while Éireamhóin claimed the north.
Amhairghin's predictions were unfortunately true, and within a year, Éireamhóin had killed Éibhear Fionn in a battle over border disputes. Amhairghin lived a mostly solitary existence in Inbhear Mór (Arklow, in County Wicklow), but a satire he had composed about the greed of his brothers reached the ears of Éireamhóin, who took offense and killed Amhairghin in a battle at Bile Teineadh (now Billywood, near Moynalty in County Meath).
Milesian blood nevertheless perpetuated itself as the ruling line in Ireland for about two thousand years, spawning such storied kings as Conchobhar mac Neasa, Cormac mac Airt, Conn Ceadchathach (Conn of the Hundred Battles), Fearghus mac Roich, and more. This makes them without a doubt the most successful invaders of Ireland to date.