Tactics Questions - Line and Column, Stacked or Not Stacked

[BigDuke66]

A lot depends on the Optional Rules you set.
But in general it's OK to stack attacking columns but not OK to stack defending lines because in a line formation only the most forward unit can fire, for others behind that unit you get an error message that it can't fire.
But what works in defense is stacking infantry in line with artillery, afaik both can fire normally as long as the infantry is behind the artillery. Same counts for skirmishers, put them in front of your line and you can fire with them.

And just to be clear, the most forward position is simply the unit that is at the top of the Hex Info Area. SO if you stack a lien of infantry & artillery the order should be Artillery at the top and infantry below it.