Quote Originally Posted by Smeel View Post
...or being filthy rich, buying the best armor.
(wasn't this the main reason? Allmost all elite units i've know of has been composed by nobles etc etc.)
There is some truth in this, but wealth alone does not a good warrior make. Often, nobles would have such wealth and status because they were leading warriors, not the other way round.

You needed to be very rich to afford the best cataphract armour, but you needed to be very fit to use it.