If the Mongols are running away in panic you should pursue since pursuers normally have a big advantage, if they are running away as part of planned strategy you should not.
What you should or should not do is better determined by whether or not it helps win the war than whether it helps win a battle. If pursuing causes your unit to leave the territory you should have been defending, the mere accident of another of their units stumbling across the undefended territory could lose you the war, without any planned strategy on their part.
It is insufficient to know their plans. You have to know your own.
If the Mongols are running away in panic you should pursue since pursuers normally have a big advantage, if they are running away as part of planned strategy you should not.
What you should or should not do is better determined by whether or not it helps win the war than whether it helps win a battle. If pursuing causes your unit to leave the territory you should have been defending, the mere accident of another of their units stumbling across the undefended territory could lose you the war, without any planned strategy on their part.
It is insufficient to know their plans. You have to know your own.