Cavalry in the ancient Rome

The following is a short resume of a very complex matter: for better knowledge I suggest http://en.wikipedia.org/wiki/Equestrian_order
We plan to insert in this blog more detailed infos under the tag "Cavalry"

Cavalry starts in the regal period as the personal escort of the king. In the beginning only patricians can be knights, because they can afford an horse; in fact they constituted a social high-rank group, the equites.
Few later, equites were divided in the ones provided of an horse from the public resources (equus publicus) and the ones with an equus privatus (but refunded with public money in case of killing in action) .
In the republican period, at a certain point, also a part of the not patrician class had to be provided with a public horse to rise the number of equites. To be in this group was considered a sort of status symbol and the legend of an ethical supremacy of the knights, starts probably at this point.
On the other side we must admit that the role of the cavalry in the ancient battles was limited in comparison with infantry, at least until the late empire period. So the amount of equites in the army has always been relatively small.
In the late republican period and in the imperial one Romans started to recruit equites from the allied populations, but equipping them with roman horses, because they were better selected.
As far as the limits of the empire were enlarging, cavalry groups (vexillationes) became more important to grant mobility, presence and visibility.
After the matches with populations that largely employed the horses in battle (Parts, Sarmats) the roman cavalry began to rise in number of knights and to change equipment in a more heavy one, going toward the so called catafracts of the middle-age armies.