I am Uncle Hyena; I live in Waukegan, which is on Lake Michigan just north of Chicago. I was born in 1956 and first read White's "The Sword in the Stone" in about 1965, and have been studying Arthur and the literature around him ever since.
Now... Can anyone tell me when this idea of Arthur's knights being Sarmatians came from? Both my wife and I are pretty well versed in this stuff, and the recent movie was the first time either of us had heard anything about Sarmatia in relation to Arthur. (Quick aside: Was anyone else amused by the fact that the two knights dead on the field at the end of the film were the two heroes created by Chretien de Troyes?) I am assuming that the Sarmatian theory is a relatively new development, as part of an effort to put horses under Arthur's men.
Stuff in my head I would like to hear comment on: If, as seems likely, the historical Arthur was the "Riothamus" who led some sort of military expedition from Britain to western Europe in 469-470, this puts Arthur solidly pre-stirrup, which means if Arthur's men were horsemen at all, they were mounted infantry. This begs the question: When did Arthur's men become "knights"? I am not that familiar with Nennius, but there is little evidence of mounted combat in Geoffry of Monmouth; I am currently suspicious that Chretien turned Arthur's "noble warriors" into "knights".