IMO the Civ series as a whole has failed to capture what war is like historically because of this. Civ 5 is the worst offender, primarily thanks to horseman spam. On the other hand, SMAC actually got it right - if you look at the base unit chassis types, some were more effective in certain terrain than others. Here are some tweaks I would make to address this: 1) Mounted units -50% strength when attacking cities with walls, -33% strength attacking cities without walls - Someone want to explain how horse-mounted soldiers can take a walled city by themselves? Maybe their horses are expert jumpers, or maybe they ride winged mounts...? Anyway cavalry are meant for maneuvering in open terrain to surround and flank the enemy, and for charging vulnerable units like archers and siege equipment, and lose a lot of their effectiveness in urban combat. 2) Infantry +25% strength when attacking cities and forts - Infantry are meant for assaulting cities, and then defending what they've taken. This modifier would encourage players to use infantry in the manner in which they were meant to be used. 3) Catapults and Trebuchets -50% ranged strength against non-city targets - Historically catapults and trebuchets were not used in the field very often, because trying to hit a moving target with them was nearly impossible. And yet in this game, they can annihilate fast-moving units like chariots and horsemen. 4) Tanks -50% strength and Modern Armor -33% strength when attacking cities - Armored vehicles are extremely vulnerable in city, because of limited sight and the fact they can be ambushed in close quarters from every direction. No WWII tank commander in his right mind would drive his tanks into a defended city without heavy air and infantry support.