To illustrate:
1) Invariably, there will be a clash of infantry lines in the battle.
2) Inevitably, some units will do better than others, generating "Push Backs" on either side.
3) These "push backs" weaken the losing unit, leading to a runaway cycle of the losing unit getting chased far behind their own lines.
4) The Winning unit (the one doing the push backs) invariably ends up on an impromptu isolated deep recon far behind enemy lines, usually with zero support to either side.
This game mechanic is so wrong, so historically inaccurate, that it's difficult to know where to begin, but I'll try:
1) No infantry unit would advance and leave it's flanks totally unguarded willingly, even in pursuit of a (temporarily disadvantaged) foe. Infantry units fight as a group, not as individuals (see Archer Jones magisterial "The Art of War in the Ancient World" for a great explanation of this). These units would not advance far without flank security.
2) This sort of wild, unguarded pursuit occurred historically among cavalry units (and perhaps among infantry after the battle was effectively over ie during a rout). It did not occur during battle - even among the most undisciplined infantry units. This is because no group of humans needs discipline to feel fear. And Fear of their unguarded, wide-open flanks is what prevents infantry from behaving like Panzers slicing into (and then roaming around behind) an enemy line.
The end result:
Chaotic engagements that bear little resemblance to actual battles. It becomes impossible to maintain any sort of ordered infantry line, because you have no control (nor does your opponent) over these crazed infantry pursuits. Even in the very early stages, whatever formation you may have will disorder itself via this game-wrecking infantry pursuit mechanic.
See the included screenshot for an example of how ridiculous this looks even a mere 2 turns after the initial clash of infantry lines.
