I too use the fire at the towers technique till all the arty is out of ammo. As for assualt troops. I NEVER use good troops. They tend to get shot to hellandgone with or without armor. It's a waste of well spent money. If is it after the first 100 years or so of the game this is a no brainer. I send the bits and pieces of mercs left from a battle unless they are still above 50% or so. Also, in HIGH, my "attack" stacks usually consist of over half of troops who have been replaced by upgrades in the "defense" stacks. I find it hard to disband these troops who have served me so well. So, they go on campaign (often punitive campaigns as I like to mainly turtle, but other powers will of course not leave you alone to the more peaceful life) with a good general. I let them die a glorious death in battle rather disband them to become mercs nobody wants. These expendable troops are sent in 1-3 units at a time through a single breach so that their lack of numbers is not as much of a hindrance (harder to flank them). I EXTREMELY RARELY lose more than 400 men assaulting even the toughest citadels. Make sure you have arty to knock that breach in the wall and the nearest towers to give your old FMAA a break! This is why I never autocalc assaults. I want to take the casualties out of certain units. When I autocalc, there seems to be no rhyme or reason to it with nearly every unit losing a few men.