Cavalry and chariots against infantry

[Macedon]

I would advise much caution when discussing gunpowder tactics. Things are tactically very different and the meaning of "a formed battle-line" in the 18th, 19th, even early 20th centuries is not equivalent to that of a Roman or Greek army, nor even that of a Gallic or Illyrian one, in order to serve as parallels. For example, lines (and columns) were nothing like a shield-wall. Their depth was very shallow, their motion much more varied as well as equipped with nothing to defend against enemy bullets and shells that would very easily disturb perfect (or even proper) cohesion. Companies, battalions... all arranged wit wide gaps for the cavalry to pass through and attack them on their rear... When that one volley of bullets was not enough to stop the enemy horsemen they would easily get trampled. Such was the fate of any infantry that did not form in compact or close ordered line in any historical time. In squares, men stood more densely exactly to that purpose and of course relatively small squares were the only solution for armies that did not form in very lengthy lines and depths, a tactic that was appropriate for maximum fire-power but did not allow for closing ranks throughout the battle-line to face charging cavalry. Furthermore, a cavalry charge in the Napoleonic years had tactical effects that were new to these weapons. For example, by charging infantry and actually forcing it to form in squares they rendered it much more vulnerable to cannon fire, which was in itself a reason for organizing such a charge in the first place.