: The bulk, if not all, of Gondor's cavalry in this battle consisted of horsemen from the Vales of Anduin (almost certainly men of the Eotheod).

Some of these, or related folk, are recorded as settling in Gondor and eventually becoming assimilated, their mounted prowess would undoubtably have been made use of by the Gondorians. Earnur was certainly mounted when he was cowed by The Witch King, this is suggestive that the upper classes, if not others as well, of Gondor had some skill in mounted combat, though they were not from a purely horse-based society like Rohan. The Rangers of the North were mounted, and the fact that they took the trouble to bring Aragorn's own horse from the far north suggests that the steeds they rode were trained war-horses (if they were merely riding horses then why go to the trouble of bringing a specific one all that way?). This suggests that mounted combat was an accomplishment of Dunadan nobility in general.
Also, as a general point, if the Gondorians realised that a mounted element in an army was desirable (as is shown by their recruitment of the Eothed) then one imagines that they would make some efforts to raise at least a modest native cavalry contingent.

: : At the time of the War of the Ring, the cavalry of Gondor are
: : mentioned counter-charging the enemy at the Battle of the
: : Pelennor Field. This charge was led by the Knights of Dol
: : Amroth though the force as a whole was mostly composed of
: : horsemen who would seem to have been part of the standing army
: : of Gondor.

: : The forces led by Imrahil seem to be wholly cavalry (he had a
: : long way to travel to Minas Tirith and it would make sense that
: : he took only his most mobile troops with him). Imrahil had an
: : unknown number of Swan-Knights (probably around 300) and 700
: : men-at-arms...

: I think 300 is too high for the knights, and the men-at-arms are never said to ride into battle.

The bulk of the cavalry led by Imrahil at the battle are not described, they could have included his men-at-arms, and possibly some of the Tower Guard (who as elite troops probably had mounted capability).

: : The term Man-at-arms is a very specific one, which Tolkien as
: : a Mediaeval scholar would have been aware of, it means a fully
: : armed cavalryman whose main weapon was the lance (in French
: : Gendarme [from which the modern French term for police comes
: : from], though as late as Napoleon's time the earlier meaning
: : was occasionally used - a heavy cavalry unit in the Imperial
: : Guard was called the Gendarmerie d'Elite)...

: Tut, tut! Tolkien was a linguistic scholar. He never called himself a medieval scholar. Someone recently contacted Tom Shippey and asked him what he thought of the idea of Tolkien as a medieval scholar. Shippey's answer (I'm summarizing) was that, if pressed, Tolkien might have conceded to being a medievalist, but not in the sense most people use the word today. But Shippey was quick to point out that Tolkien thought of himself as a philologist, and often said so.

He was a scholar specialising in a language which was first written down in around 650 AD and ceased to exist as such by around 1200 AD. I think he was perforce well versed in the Mediaeval era.

: That is really a small nit, but I don't think it's necessary to imply that Tolkien was a medievalist for this point, Martin. I don't know the etymology of "man-at-arms", but Tolkien's philological background would have acquainted him with it.

I think it is well acknowledged that Tolkien was careful in the language that he put down on paper. By the time English began to be used in written form again the Latin term miles (meaning a fully equipped heavy cavalry man) and the French term gen d'armes were translated as man-at-arms. I don't think Tolkien would have been unaware of this meaning. It is at least possible that Tolkien was using the term in this sense. Nothing in the text is directly contrary to this at least. A man might be perceived as tall even when mounted, particularly if his feet trailed on the ground like Hrolf Ganger (Rollo) the founder of Normandy!

: Nonetheless, he did not feel constrained to abide by the rules, and when Tolkien described the men of Dol Amroth as they marched into the city only the knights are said to be riding horses. The men-at-arms followed, seven hundred strong, "tall as lords, grey-eyed, dark-haired, singing as they came."

: As an aside, it may be significant that the swan-knights' horses were grey (like the Rangers of Eriador's horses). Also, I don't know if anyone has ever commented on the applicability of the image of the swan to the knights. These may all have been men descended from Galador. The swan was an image favored by the Teleri in both Aman and Middle-earth (Cf. Galadriel's boat in Lorien).

The emblem of Dol Amroth was a swan-prowed ship, undoubtedly a Telerin device.

: That is not an argument for or against the men-at-arms being mounted, btw.

: :...The man-at-arms could be of any social rank the only
: : qualification was the possession of complete armour and a large
: : war-horse, this tends to support the distinction of the Swan
: : Knights as a social, rather than merely military, elite.

: This, I think, is a good reason why the swan-knights may have been men of special descent, but it's only a speculation.

: : Tolkien mentions that the inhabitants of Minas Tirith were
: : unused to the sight of horses in their city. This should not
: : be taken as proof that Gondorians were ignorant of horsemanship
: : or did not make use of cavalry to any great extent. A cursory
: : look at Minas Tirith, a city built on a conical hill with a
: : series of terraces with winding streets, shows what an
: : unsuitable place for horses it was. No doubt stabling existed
: : beyond the city walls in Pelennor, and even the nobility would
: : be forced to take to foot once inside the city proper.
:
: Agreed. In fact, there is reference to stables at the forts for the beacon towers in Anorien.