The Celtic people said they were the progeny of the Tuatha De Danann, whom they defeated, took prisoner, forced the children to make weapons for them and took their women as their wives.
The Mycenaeans were the Celtic people (DNA confirms it). They founded a great civilisation called Mycenae which eventually collapsed for the usual reasons. They then became the Greeks and for 2000 years people forgot they were originally Celtics (The "Keltoi"). Some people believe the Homerian myth cycle itself originates in the war between Cro-Magnons and Neanderthals and later got transported from Northern Europe to a different setting.
The Greeks made Greece great and the Greeks didn't even know the entire time they were originally sea-faring Celtic peoples. Greece collapsed in the usual cycle and the whole of the Greek people were taken into slavery by the Romans.
The Romans were made great for only one reason and it was their Greek slaves. The Greeks were responsible for nearly every single great achievement the Romans are credited with but they don't get credit because Romans did not countenance Greeks.
The Roman Empire collapsed and the best Greeks fled to found Byzantium, one of the most important civilisations of the ancient world. The Vatican church forged historical records to conceal the truth - Byzantium was never a theocracy. It was a Republic. Kings were revered as protectors of men's rights in Byzantium and when they stopped protecting men's rights they were overthrown. Byzantium was one of the wealthiest and most prosperous in the world and starvation was unknown there. The Byzantines were crusaders for truth and justice, forbidding slavery and sending armies out to crush slave strongholds worldwide which were entirely dominated by Jews. Many of the slavers fled and ended up in Holland where they eventually formed the largest slave trade the world has ever known centuries later dealing in white European slaves and slaves from Africa. The Dutch slavers held a monopoly they defended with private armies of their own on the slave trade. Don't believe the fake history you read about Byzantine slavery. It is nothing but fabrication using the Slavs and Bulgari captivity and transporting it from Russia to Byzantium. Remember, Byzantium was hated and envied by nearly everybody around it including both Jews and Catholics and they were the ones who got to pretend to record parts of its history. Byzantium had serfs, not slaves and this academic was risking his career publishing a truth that is forbidden by the people who control education. I read this book and it was obvious the Byzantine slave markets were an invention of the Vatican no more real than Wyverns and Dragons. In Byzantium you could join a house as a serf and all your needs in life would be taken care of. It wasn't slavery because a serf could walk away from these houses any time they wanted to. For people with few economic opportunities it was a stepping stone to a better life. Many of these "serfs" went on to positions in the royal court and government and their sponsors provided the network of contacts they needed to get these appointments. Remember that one of the most important reasons for modifying history can be that the tyrants who rule today don't want you to find out that the past may have been much better, instead of worse as they always like to teach.
If you wonder why the Jews hated Byzantium so much they'd still be slandering it 2000 years later, it was because of two bodies of law in Byzantium called the Theodosian and Justinian codes forbid them to do many things they had historically made nice livings off with a special emphasis on outlawing usury. Note that as in Spain under the Inquisition, Jews could have left Byzantium any time they wanted to, including relocating to Palestine. Large numbers of Jewish people in Byzantium were executed when they were found to be dealing in Christian slaves. As revenge, they saw to it Byzantium entered the history books as a "nation big on slavery." As always, the exact 180 degree opposite of the truth. (If you read the heavily biased Wikipedia entry above, you will discover in the details that despite centuries of strict guarantees of their security as they lived in Byzantium, Jews were foremost in forming a fifth column to support Muslim invasions and worked to supply them with weapons, resources and intelligence, eventually being the main reason Byzantium was finally destroyed by a huge coalition of forces all around it while still choosing to live inside of Byzantium for decades and pretend to be loyal citizens.)
Byzantium lasted a long time (beyond the usual 200 year limit) but eventually collapsed. The Byzantines were scattered all across Europe and by this time the nation formerly known as Greece was occupied by entirely different races of people who had little or no original greek ancestry.
When you take the lens of the Catholic Church away from your eye and look at history again, the most advanced civilisation of the ancient world before the Dark Ages (a real theocracy) was absolutely Byzantium. Not Greece or Rome. Everybody on the planet has a vested interest in keeping you from the truth - the most advanced of all the civilisations of the ancient world was A Christian Republic called Byzantium founded mostly by original Greek people.
The common thread running through Mycenae, Greece, Rome and Byzantium was the Greek people, a race of Celtics who had forgotten where they were from.
What about their legends of having come from the defeat, conquest and enslavement of the "Tuatha De Danann?" Was there any truth to it?
We need only look to what is called biologically "The Greek Foot." The Greeks were stronger, more muscular and had far harder bones than the Romans. They were chimney shaped whereas the Romans were broad-shouldered.