Infantry Squares may not advance and attack Cavalry. Why?
Historically:
According to regulations, Inf. Battalion Square - it is the static defensive battle order against cavalry charges.
Physically:
1) The first files on all four sides of a fighting square normally stood on one knee. So, the men could not move.
2) The moving square loses its order and cohesion and could be the easy prey for cavalry. That is why men in square might move very slow - step-by-step only.
As you understand, this temp of stepping is good just for the slow retreating at best and nothing else.
