In the invasion of Eriador by Gondor against the ascendancy of the forces of Angmar one whole division of its army was cavalry, which operated in a pincer movement independantly of the infantry of the main body.

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. 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). 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.

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.