Horseman

"Day was the grandeur that was borne before the horse as he galloped, &ensp;the eastern ocean gave it birth; &ensp;night was the grandeur that was borne behind him &ensp;and its birth was from the other waters."
 * &mdash;The Upanisads

Overall strategy
Cheap yet weak, Horsemen are a form of militia available to most factions. Horsemen are weak and thus only best used for scouting, as well as interdicting enemy light infantry (but not spears or melee units). Their slow plodding pace and their lack of robustness means that you will be keeping them mostly as a defence force, or as a last-ditch strike team should the need arise — just don't expect them to work well against other enemy cavalry.

Replacements:
 * Konnica: Most Slavic factions have access to Konnica, which have added hitpoints but poor attack against enemy cavalry.
 * Kushite Lancers: Faster mobility, and better attack. But is costlier.
 * Bek Cavalry: Is a fairly tough cavalry unit, and substantially stronger.
 * Arab Cavalry: Melds the best qualities of both Horse Retinue and Horseman, but is sitll slower (38 frames)
 * For some factions, like India and Srivijaya, Horsemen are absent.