A question about warhorses: historically were there problems with using stallions?

throughout history people have been using horses in wars for everything from travel to battle, but knowing that stallions can be very temperamental i was wondering, were mares used more often than stallions? or were most of the male horses geldings? if not, is it possible to train stallions well enough not to fight with other stallions or try breeding with mares whilst a rider is mounted on them? for some reason i imagine that military figures with a high status (like generals) would have rode stallions as a symbol of power, but i could be wrong. does anyone know much about warhorses?