Quote Originally Posted by Myth View Post
Historically speaking they were not vulnerable but rather more dangerous unless one is equipped with a bill and can hook the rider off his horse. A typical heavy cavalry rider would be on a large (as in VERY FREAKING LARGE) destrier horse, which itself is a weapon. He would have a lance, longsword and a light mace, which used one handed but with the momentum generated by the horses' movement, ended up in heavy trauma to the head of the unfortunate infantry below (armour does not help vs bluntgeoning weapons that much).
of course, you don't describe what weapons the infantry will use, if that was medieval period, I'll asume everyone had some knowledge how to create makeshift polearm from broken swords and spears