All That:

The most information is from a very bad source, a late 8th century collection by a monk called Nennius. He calls Arthur a "war-leader" (but not a king), and lists ten battles he fought in; most of the places cannot be identified, and only the last of the ten battles, Badon Hill, has even a vague date (500, more or less). Nennius says that in that battle Arthur slew 960 men single-handedly - that element, along with the inability to identify places or dates for the other battles, leaves us still short of hard historical data.

The best and most contemporaneous chronicle for the period around 500 is by Gildas, but he never mentions Arthur by name - although he does cite the battle of Badon Hill, at a point in time more or less compatible with Nennius.

There's an entry in a 10th century chronicle about a battle at "Camlann, where Arthur and Medraut fell." (Medraut is Mordred, but note the chronicle doesn't say anything about any blood relationship, or betrayal, or even if they're on opposite sides.) The entry is for 539, which is a bit late to match the dates in Nennius, above.

Otherwise, there are references to Arthur in a few Welsh heroic poems and triads, but they don't really tell about him, they just imply that everyone knew about him.

So for years, although historians worked over all the British materials they could find, an historical Arthur has remained nothing more than a name at best. But in recent years some historians have tried looking outside Britain for traces of Arthur, and have made some very interesting connections. In this article I will briefly mention two new theories of the original Arthur. (They're about 20 years old, but that's "new" in context.)

Riothamus
In Geoffrey of Monmouth's story, Arthur undertakes several campaigns in Gaul; in fact, Geoffrey makes rather a big deal about them, having Arthur pretty much conquer the Roman Empire. Historians have usually assumed, not unreasonably, that these parts of the story were pure fabrication. But because Geoffrey gives a somewhat specific timeframe for them - he says they took place while Leo I was emperor in Constantinople, and a few other clues - and because a campaign by Arthur in Gaul is also referred to in a separate source (the prologue to the life of a Breton saint, written in 1019), historian Geoffrey Ashe tried looking at continental history of the time. He found that there was indeed a king of the Britons who led a large military expedition to Gaul at exactly that time, the reign of the eastern emperor Leo I.

Granted, there are a few inconsistencies between this historical figure and Geoffrey of Monmouth's account. For one thing, he's called Riothamus, not Arthur; he fights with the Romans, not against them; and his expedition takes place in 470, far too early to jibe with the dates of Badon Hill and Camlann. On the other hand "Riothamus" is a Latinization of a Celtic phrase for "high king," so this may be a title and not a name, and so he could still be Arthur; and Ashe can rationalize the discrepancies of date to some extent. So it may be worth looking a little closer at the similarities.

Riothamus has the same distinctive title attributed to Arthur, "King of the Britons," and there is only a relatively short window of time when this title could have been used at all plausibly: the roughly 30-year period when the Saxons were firmly established in Britain, but only on the eastern fringes. Before then, the title would have been "King of Britain;" afterwards, the British peoples were too weak and fragmented to be united under one king.

Historically, Riothamus's campaign in Gaul ended disastrously: he was betrayed by the Roman prefect Arvandus, attacked by the Visigoths before he could link up with his allies, and forced to retreat into the territory of the Burgundians. (Note the similarity to Mordred's role in legend: the treacherous deputy ruler, who betrays the king to the barbarians.) And we never hear any more from Riothamus after the retreat: he disappears into the mists of history, heading for a Burgundian town named Avallon.

The Sarmatians
Another novel approach to the Arthur question started from military considerations. Heavy, armored cavalry of the sort attributed to Arthur were unusual for the time and place: what would they have been doing in post-Roman Britain? The traditional answer was always that they hadn't been there, that they were a later addition to the story, from the Age of Chivalry. But some historians have tried looking for a heavy cavalry presence in Roman Britain, one that might have survived into post-Roman times, and they found one: a unit of 5,500 Sarmatian cavalry, posted to Britain in 175 as auxiliaries to the VI Legion Victrix. After retiring from the army, instead of going home these Sarmatians settled as a colony in Bremetannacum (the modern Ribchester, in Lancashire), an enclave which was still referred to in 428 as a "troop of Sarmatian veterans" (cuneus veteranorum Sarmatorum).

And who were the Sarmatians? They were a nomadic people who lived in the area of modern Hungary in the first and second centuries. What was distinctive about them for the time and place, was that they were fully armored: both man and horse went into battle wearing close-fitting scale armor.

Once we realize that there in fact were heavy cavalry in Roman Britain, and that the Sarmatians preserved their ethnic identity well into the 5th century at least, then we can consider some other Sarmatian parallels with the Arthurian legend:

Instead, I've tried to show that "History" is not frozen, not a complete library of books which, if we only had the time to read them all, we would then know in full. It's a living, dynamic field, which needs insight and interpretation as well as reading and research to grow. Don't assume the "Creative" in our name has to mean "fantasy": there's plenty of room - even need - for Creativity in the real study of history.

But speaking of fantasy, what if both theories were true? Wouldn't it be amazingly cool if the historical Riothamus were also a Sarmatian descendant? Well, that might be stretching things a bit far....

Geoffrey Ashe first articulated his Riothamus theory in an article, "A Certain Very Ancient Book," in Speculum, vol. 56 (1981). His subsequent book, The Discovery of King Arthur (1985), develops the theory at length. Or see his articles at www.britannia.com/history. There is also a copy of correspondence from Geoffrey Ashe discussing some criticisms of his theory at the Arthuriana journal site.

In Britannia's Sources of British History there is a letter from Sidonius Apollinaris, Bishop of Clermont-Ferrand, to Riothamus and an extract from Jordanes' Gothic History (c. 600) that refers to him.

I first heard the Sarmatian theory presented by Helmut Nickel, curator of arms and armor at the Metropolitan Museum of Art, to a bunch of us sitting on the floor of Marian of Edwinstowe's apartment in the fall of AS XI (1976). If you weren't there yourself, you can find more information in the book, From Scythia to Camelot: a radical reassessment of the legends of King Arthur, the Knights of the Round Table and the Holy Grail (1994) (honest, that's just the title, not the whole book!), by C. Scott Littleton and Linda Malcor.

Online there are two articles by Linda Malcor about Lucius Artorius Castus in issues 1 (spring/summer, 1999) and 2 (fall/winter, 1999) of the Heroic Age ("a journal of early medieval northwestern Europe") archives.