Bront, you have no idea how much I want to address your post, but I'm dealing with many of the issues you raise in my "Aquiromian Holiday" series on my personal blog. I've been using "The Phoenix on the Sword" to discuss the alleged Ancient/Classical milieu of the Hyborian Kingdoms, but a story you bring up, "Black Colossus," has so many quintessentially and indisputably Medieval elements that denying them would be untenable.
Briefly: there is zero justification to say that the Ancient elements of the Hyborian Age kingdoms in any way override, overshadow or otherwise take precedence over the medieval elements. You cite cataphracts, as if Howard's mention of knights should be taken as "really" meaning the heavy cavalry of the Persians, Sarmatians and such. However, a reading of Black Colossus would (or should) assuage any doubt that Howard was fully intending his knights to be knights with a capital (silent) K:
There were the knights, gleaming in richly wrought plate-armor, colored plumes waving above their burnished sallets. Their steeds, caparisoned with silk, lacquered leather and gold buckles, caracoled and curvetted as their riders put them through their paces. The early light struck glints from lance-points that rose like a forest above the array, their pennons flowing in the breeze. Each knight wore a lady’s token, a glove, scarf or rose, bound to his helmet or fastened to his sword-belt. They were the chivalry of Khoraja, five hundred strong, led by Count Thespides, who, men said, aspired to the hand of Yasmela herself.Plate armour, plumed sallets, caparisons, caracoles, pennons, lady's tokens, chivalry: you couldn't get much more Medieval if you tried. If you can find any classical sources that could even be arguably interpreted as analogues, I'd like to hear them.
You mention "lordly stone castles overlooking rustic hamlets with their peasant populations" being the last thing on your mind. Really? Even after reading passages like this:
As the villages thinned, the land grew more rugged, and the keeps that frowned from eminences told of centuries of border war. But none rode down from those castles to challenge or halt him. The lords of the keeps were following the banner of Amalric; the pennons that were wont to wave over these towers were now floating over the Aquilonian plains. Guess you and I are reading different stories.
This attempt to give the world of Conan a more medieval cast seems to be a recent phenomenon and is an attempt in large part, to pander to the new wave fantasy crowd who jumped on board during the revival of High Fantasy literature in the late 1980’s. Look at some of the threads on this forum and you will find politically correct subjects about Conan’s treatment of women, or what Conan tale should I recommend to my wife or child. It is a modern cultural thing. I’m sure The Hobbit will do well on the silver screen ( one medium where Conan unfortunately will always miserably fail ). It is a little like some people are embarrassed of Conan and the Hyborian Age and want to re-imagine the whole thing.
I have a rather different interpretation: I think that the "ancient" Hyborian kingdoms misrepresentation is a mistake that has persisted for far too long. I'm also disquieted by your reference to "politically correct" topics regarding Conan's treatment of women, and that you seem to assert Conan will always fail on screen - as if there's something inherent to Conan, not Hollywood's stupidity, which causes it. Most of all, though, is this implication that applying Medieval aspects is endemic of some sort of agenda of embarassment, as if we want to re-imagine Howard's creation so it "fits in" more with established fantasy, which is just so wrong-headed as to be somewhat astounding.
I see a bit of contradiction here. On the one hand you are saying that having some medieval style weaponry in the Hyborian Age proves a medieval basis for many parts of that age, and yet you argue that classical elements proves nothing.
This is because, despite your conflation of the cataphracts with knights, you can have "classical" things in Medieval settings, but not the reverse. You can have ballistae, legions, "imperial troops," temples and whatnot in a classical and medieval context, because both existed in those periods. A lot of technologies, institutions and inventions from the period carried on into the Middle Ages. But you can't have Medieval elements in a classical context, for obvious reasons.
Not to speak for Deuce, but the fact of the matter is that the medieval elements vastly outweigh the classical elements when it comes to the Hyborian kingdoms.
We have references to legions, imperial troops, imperial squadrons, mystery cults, and temples - all things which existed, in some way or another, in the Middle Ages as well as Classical period. But we also have references to things that are quintessentially Medieval: knights, pennons, seneschals, lady's tokens, batons of authority, high councillors, peers, caparisons, burgonets, bascinets, sollerets... Where are the manicae, centurions, consuls, phalanxes, aquilifers, gladiators, fasces, gladii, praetorians, senators?
Howard didn't talk down to his audience, so if he intended the Hyborian Kingdoms to be classical, then we wouldn't be having this conversation, because Howard wouldn't leave the reader in any doubt. Are there classical elements in the Hyborian Kingdoms? Of course, just as there were classical elements in the Middle Ages themselves. Were the Hyborian Kingdoms more Classical than Medieval? Were Tarantia, Belverus and Shamar more like Carthage, Rome or Babylon than - say - Orleans, Prague or Toledo? I'd say not.