Very recently, a man - John Matthews - who has devoted decades to studying the Arthurian 'legend' has become convinced that the Knights of the Round Table were exiled warriors and horsemen from Sarmatia, which is nowadays called Georgia (the 'Russian' one, not the one in the USA!) They had a leader called Artorius (Latin for Arthur), they worshipped a sword supposedly embedded in a stone and another which was thrown into water, just like Excalibur. There are other elements which are very similar, too. When the Romans invaded Britain, there were, apparently, about 3000 Sarmatians amongst them.
So, for what it's worth, there just may be an element of truth in the old legends after all!