The Celts are a group of people who primarily inhabited the extreme northwest part of Europe
for over a millennium
between approximately 500 BC and 600 AD. The history below is that of the British Celts as that's what I know. At the end there is a brief mention of Celtic groups elsewhere in Europe, if someone is able to fill in information about them I'd be delighted.
Where the Celts came from is unsure, although central/southern France or northern Spain are the most likely contenders. Why they left their homelands is also unknown, but we do know that by 500 BC there were well-established and settled Celtic communities in northwest France and the British Isles, where they probably quickly assimilated the native Stone Age peoples.
The Celts were skilled farmers and bronze-workers, and the intricate knotwork designs they produced are still very popular today. They were an apparently peaceful people, although their primary religion, Druidism, placed an emphasis on sacrifices to the Gods, including human sacrifice.
The traditional Celtic way of life was torn apart by the comnig of the Romans under Julius Caesar: first conquering Gaul and the mainland Celtic kingdom of Armorica (roughly modern-day Brittany), and then within a few decades taking the island of Britain. Many Celts retreated to the remote wildernesses where the Roman influence was weak or non-existent: Kernow (Cornwall) ,Scotland, Wales or even overseas to Ireland.
Roman tolerance for other religions was pushed to its limits by the Druids, and eventually the Roman Governors of Britain decided that the ritual sacrifices had to be ended. A legion of troops was despatched to the Druid's spritual holy land, Ynys Mon (the island of Anglesey) where after a short and bloody battle the Druid priests were slaughtered. The Druids believed that writing down the knowledge of their priests would cause their powers to fade, so with the massacre on Ynys Mon almost all knowledge of Druidism was lost. In addition a new religion, Christianity, was starting to gain an audience amongst people whose lives had been turned upside down.
When the Romans started to withdraw from the extreme edges of their empire a few hundred years later, the Celts returned to claim the land they saw as rightfully theirs. Their recolonisation was short-lived however, as the same Saxon warriors who were harrying Rome from the north now sailed overseas to begin a colonisation of eastern England. In the years between 450 AD and 600 AD a series of increasingly bloody battles were fought between the Celts and the Saxon invaders.
This was the time of legend, the time of the great warrior Arthur (a tale later usurped by medieval Christian writers to create the story of King Arthur), of princes and battles. Gradually the invaders started to win, and the Celts once again started to retreat to the extremes of their territory. Many fled to the now-revived kingdom of Armorica, others fought skirmishes from the bogs and moorland of Kernow. The majority of Celts ended up in the mountainous, remote regions of Wales, Scotland and Ireland, and the native Gaelic languages of these areas is derived from the ancient Celtic tongue.
Other Celtic peoples
Besides Ireland, Wales, Scotland, Kernow and Armorica there are Celts found in a few other surprisingly disparate parts of Europe:
- Galicia, in northwest Spain. The population speak Galician which is a mixture of Portuguese and Gaelic, and there are strong Celtic customs
- Galatia, in modern-day Turkey: the Celtic language was still spoken here until the 15th century, many Celtic customs live on
- Iceland is known to have been settled by Celts at about the same time that Viking invaders were also settling there. The two populations seem to have lived peacefully side-by-side