This post is about different books than the one Marco is writing.
In the Narnia books the land of Narnia is described as a small country on the margin of a great empire, the land of Calormen. We are never told the extent of it, but in The Horse and His Boy Shasta and Bree travel north for ‘weeks and weeks’ along its coast from a spot which seems far from its southern edge, while Narnia itself is the sort of place which can be crossed in a few days. ‘It is not the fourth size of one of your least provinces’, as Prince Rabadash tells his father the Tisroc.
Calormen is far larger and more populous than Narnia and Archenland, where humans first appeared on the world. And, while throughout the history of Narnia the inhabitants of these little countries continue to resemble King Frank and Queen Helen- that is, to look and act English- the Calormen are people of Middle Eastern appearance. While Aslan is remembered and revered in Narnia and Archenland, the Calormenes are heathenish in their habits, with manners resembling those of the Ottoman Turks.
Where did this vast empire come from?
Why do its inhabitants look different?
And how did they come by such different customs?
In many thousand years, one might reasonably expect people to swarthen and grow heathenish, simply by dwelling in hot countries Aslan does not deign to visit. This timeline, however, while possibly apocryphal, provides an awkwardly short interval for this huge country to be populated and develop such a distinctive culture.
If we are to accept the dates in this timeline, another hypothesis is necessary.
In ‘The Magician’s Nephew’ it is stated: ‘King Frank and Queen Helen and their children lived happily in Narnia and their second son became King of Archenland. The boys married nymphs and the girls married wood-gods and river-gods.’
For one thing, this contradicts the timeline: but it is easy enough to argue around that. Now, the timeline tells us:
204 - Outlaws from Archenland travel across the Great Desert to the South and establish the kingdom of Calormen.
It would be reasonable for even a smallish band of outlaws to increase to the few millions needed to fill up Calormen over four hundred years or so. But outlaws in mid-twentieth-century fantasy worlds are usually male and unlikely to form decent breeding populations. However... coming from a time when it might not have been unusual to interbreed with demihumans, perhaps the dark complexions and distinctive cultural traits of the later Calormenes come from non-human ancestresses?
In Narnia and Archenland, which have a European climate, the demi-human population is drawn from (Non-Christian) European mythology; in the deserts of the south, is it not reasonable to expect demi-humans out of the Age of Ignorance? All the curious things out of the Arabian Nights and the pre-Islamic pantheons one can read about in the introduction to Sale’s ‘Koran’. I postulate that this band of outlaws from Archenland got the ancestors of the Calormenes upon lovely fire-goddesses and air-goddesses, ifrits and djinni, in the southern deserts and jungles. The lesser Gods and Goddesses of the Calormenes mentioned in The Horse and his Boy- Azaroth and Zardeenah- may well be deified ancestors from this time.
Tash is another matter. While the worship of the lesser deities seems to have fallen by the wayside by the time of The Last Battle, we get to see Tash making a personal appearance, in all his icky vulture-like four-armed glory. He is obviously not a mere deified ancestor. Given the claim of the Tisrocs to be his descendants, there may be a stomach-churning non-PG-rated kind of story in the remote past of their line. If I were to write it, I would associate it with the only other bit of Calormene history C. S. Lewis (or Walter Hooper) has put in this timeline:
302 - Aslan turns the Calormenes of Telmar, who disobey his principles, into non-speaking beasts.
Anyway, enough of that sort of thing.
I think the tombs of the ancient kings outside of Tashbaan are associated with a people of more Narnian/Archenlander culture. They are called ‘ancient kings’, not ‘ancient Tisrocs’, or some other eastern-sounding title. ‘Kings’ are what they have in Archenland and Narnia. I am guessing that the tombs were associated with the original Kingdom of Calormen, that the line of the Tisrocs and associated worship of Tash arose somewhere further distant to the south, and that the Tisrocs took over this Kingdom as a going concern. Conquest is the usual way in which slave-owning cultures arise, after all, and if the Calormen culture is meant to be modelled on the Turks, it makes sense for them to be a nomadic people who rode in and took over. The Tisroc’s empire is probably not that old at the time of The Horse and His Boy. The Tisroc says ‘More than five Tisrocs in Tashbaan have died because their eldest sons, enlightened princes, grew tired of waiting for their turn,’ as though ‘more than five’ was a significant number. This suggests to me that there probably have been no more than 20 or so Tisrocs reigning in Tashbaan before that time, and their reign there began no earlier than c.600 by the timeline; probably closer to 800.