I think an ambush mechanic would add more risk to being the attacker during combat and make warfare somewhat more interesting than it currently is.
I think the way to do ambush would be to make a Dice roll when the battle start and based on factors such as terrain and leader traits the attacking army could be ambushed.
An ambush would mean the attacking army can not reatreat so losing the battle would be a stackwhip and also give a -3 or so to the Dice roll instead of terrain penalty and river penalty.
If the defender reinforce the army the ambush would end and if the attacker reinforce the army the ambush would continue.
I think the way to do ambush would be to make a Dice roll when the battle start and based on factors such as terrain and leader traits the attacking army could be ambushed.
An ambush would mean the attacking army can not reatreat so losing the battle would be a stackwhip and also give a -3 or so to the Dice roll instead of terrain penalty and river penalty.
If the defender reinforce the army the ambush would end and if the attacker reinforce the army the ambush would continue.