if you do this then the enemy will attack you in his desperation, but if you keep him running he wille exhaust and you can take him as a prisioner without losing any men and you can then ransom this prisioner and earning a bit of money. anyways the game doesnt support the later action while it atleast enables you to do the other one with telling your soldiers to attack again so it would make more sense to havbe the decition after a battle to let the soldiers fleeing get away or to follow them with the later letting you follow them for like 3 hours but when these hours are over you will get them as prisioners without any fight, as long as their strenght (measuring with an actual strenght and not army size) is only a quarter of your strenght. though to make it even bette the majority of the enemy shoulf flee and survive so if you follow these much enemys it will be like a normal chase. or something like this