yes, cavalry units should be effective against common armed infantry. spearman especialy phalanx type was in use becouse of their effect against cavalry, so about cavary penalty when fighting them should be no discusion.

and another anoying thing in rtw is militia hoplites, this is just logical error but i hate it anyway. i mean if they were soldiers enough to form a phalanx that should mean that they were welldisciplined, and that they had good morale, becouse morale come through the force of discipline. but no, they are weak as hell, they lose one bloody man and start fleeing, not to mention that light cavalry unit strike them from the front, and they are
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suposed
to be effective aggainst cavalry. to form a phalanx u need some training, to do some training u must learn about discipline, and fact that it saves your life, through that lessons u are to become better troop, but no, they are weak, too weak and too useless.