How Effective were Spears Against Cavalry?

[Macedon]

Actually, they usually did have missiles. Byzantine armored lancers, cataphracts included, were also equipped with bows. And do not forget that in medieval times it was the cavalry which was supposed to be fully armored, not the infantry, so a cataphract or a western knight trotting or pushing into a line of ill-trained, mostly unarmored or light armored footsoldiers could scare them away with his mace and sword. If they stayed put, even badly armored foot usually bested armored cavalry, but very often they did not, being peasants against nobles renowned for their fighting skills. This fear, derived from the usual vast gap between infantry and cavalry regarding their experience, training and equipment is largely responsible for the "myth" (up to a point) of the all-charging cavalry and the mistake people often make to broaden their conclusions in other eras and cultures.

Yet, cavalry was first and foremost supposed to fight against enemy cavalry and not infantry. In most ancient battles we see that it is horsemen with javelins (the bulk of ancient cavalry, even those we would call heavy) which they used against infantry and cavalry alike. The Heteroi / Companions of Philip and Alexander, armed with a long spear were never attested to have been used against massed infantry as most people think! What they usually did was attack the enemy cavalry, which used to fight a skirmishing battle (not in skirmish order, just closing in, discharging of missiles and then retreat back to their original positions as other squadrons galloped in) were at a disadvantage against the Companion's longer, sturdier spear. this was the role of the lancers... to attack enemy cavalry.