Arthurnet has long been privileged as the site of a debate over the Alano-Sarmatian hypothesis about the growth of the Arthurian legend.

On August 24, 2004, the moderator, Judy Shoaf, decided that the current debate was reaching a point of painful repetition and rhetorical attacks which was no longer doing anyone much good. Therefore, discussion of the "Sarmatian question" has been banned from the ARthurnet  e-mail list for the indefinite future. Those who wish to examine this hypothesis are encouraged to join the list   http://www.dragonlordsnet.com/kachat.htm
which is run by Dr. Malcor, one of its main proponents. This page also offers bibliography and other information.

The following is a rough explanation of the hypothesis, and a partial explanation for the problems it poses to civil discussion.

   The Alano-Sarmatian hypothesis proposes, more or less, that the original, historical Arthur was a Roman military leader named Lucius Artorius Castus, who served as commander of a group of Sarmatian warriors (from what is now Iran and Russia) for two years in Britain, around 182.  Castus probably led this group in battle several times, though he left Britain for other commands and eventually died in Dalmatia. The theory proposes that the Sarmatians in Britain continued to live there, possibly employed by the Roman military, possibly maintaining their nomadic ways and their own language, but at any rate telling their traditional stories with a new hero, Castus, called by them Artorius. Although the stories of Arthur were incorporated into British history as those of a fifth/sixth-century British military leader (Welsh annals and Historia Brittonum, aka "Nennius") or king (Geoffrey of Monmouth) leading a confederation of British kings against the Germanic invaders/colonists, they are thought to contain information about the actual brief career of Castus in Britain, or perhaps of subsequent leaders of the Sarmatians nicknamed or actually named Artorius. According to this hypothesis, the emphasis on horsemanship in the later legends does not reflect high medieval chivalry but rather the horsemanship of these steppe nomads.
    The hypothesis further proposes that, around the eleventh and twelfth centuries, the Artorius stories were combined with similar sagas told by people on the Continent descended from the Alans, a cultural group from the same region as the Sarmatians and with similar folklore and mythological traditions. These Alanic stories would include motifs such as a sword stuck in the ground and a sacred cup (possibly associated by Christian Alans with the Crucifixion), and women who dwell in watery places who help warriors. The assumptions here are that (1) these motifs are exclusively the property of the Alano-Sarmatian group and their modern descendents, and (2) these stories could become attached to Arthur only if he was originally the hero of that kind of story, i.e. a saga of Sarmatian origin. Thus Arthurian literature would have been born out of the meeting of two strains of the same type of legend, one told by Sarmatians in Britain about a man named Arthur, the other told on the Continent by Alans about several heros, including Lancelot. This would explain why there was such a sudden flowering of Arthurian literature in the twelfth century, when in fact political and economic conditions brought English, Anglo-Norman, Breton, and French cultures into contact.

Discussion problems: rhetoric
    According to the defenders of this hypothesis, anything in Arthurian literature which can't be traced to these story types is irrelevant "overlay." If a Welsh poem speaks of Arthur travelling to the otherworld to rescue a cauldron, the story is "overlay," a borrowing of the name Arthur for a plot that does not really belong to him; if the same poem mentions Cei, that might be an authentic detail about Castus, who might have had a brother named Caius, and therefore part of the "core" of the legend. However, for those primarily interested in the Welsh texts themselves as integral works of literature, or for the information they offer about the culture and traditions of those who composed them, these Arthurian works are of great importance, while their significance as "proof" of Sarmatian influence is trivial.
   There is also a considerable redundancy of explanation: for example, the sword cast into the lake is insisted upon as an Alano-Sarmatian motif, but it would have been extremely significant to British audiences, since the peoples of Britain had been making ritual deposits of swords in lakes since long before the coming of the Romans. Similarly, some names in the legend can be interpreted both using Celtic language roots and using Alano-Sarmatian or Latin roots.
    Thus it can be seen that two sides easily form. One claims that only the Alano-Sarmatian material is of interest and that anything that can be interpreted as Alano-Sarmatian must be added to the "core" and is no longer part of the heritage of British folklore and story. The other is deeply offended by this attitude and insists on a more traditional examination of the relationships between the Arthurian legend and the cultures it purports to represent. A great deal of anger and ill-will has resulted, not only in these two parties, but in those who are not amused by the constant attacks of one party on the other. Notably, Dr. Malcor will never allow anyone to contradict her without contradicting them back.

I think it is important to realize two more things:

(1) Most professional Arthurians are concerned primarily with Arthur as a literary figure, not with possible historical prototypes. Whether there was a historical Arthur is (almost) COMPLETELY IRRELEVANT. Even if we had hard evidence--if another book by Gildas with a chapter on Arthur (Sarmatian or British) turned up, this would be true. Such a book would be of great interest to the popular mind and to historians of early Britain, but minimally so to those who study Arthur.

(2) The (almost): Before the Sarmatian theory it was possible to say "there might have been a historical Arthur, a Romano-British/Celtic (OED 2) warlord living around 500." Now you have to add another clause, "...or the story might have originated with a second-century Roman officer who commanded some Sarmatians in Britain for a couple of years around the year 200." That is, for most of the 20th century we had a small certainty that there was a historical Arthur who gave rise to the legend, who led the Britains to a moment of peace in the 6th century; now we have lost that. Aside from any scholarly picking, this is sad and perhaps explains why few are indifferent to the theory.