The focus on cities is imperfect, however. Because there are few on-map resources to control, cities are self-contained production engines that drive your war effort. In the Heroes of Might & Magic series, the turn-based system to which Kohan is sometimes compared, castles are essentially useless without the special resources that can be found only in mines scattered across the map, and simply marching from castle to castle does you little good if you don't have the resources to take advantage of a castle's production. Kohan's improvement-based system means that taking enemy cities will rapidly shift the balance of power in your direction, and the most effective way to do that is by massed force. In the end, there is less maneuvering and tactical gameplay than there could be.
A problem with the Kohan combat is that while units have certain special bonuses (for example, paladins are more effective against shadow units), these bonuses are not enough to overcome the standard real-time strategy focus on sheer numbers. Kohan is still about building the largest army (regardless of composition) and throwing it at the enemy.
Hero units are also not powerful enough to make up for enemy numbers.