I don't understand why the weapons on my units (especially air and naval) can't be improved to be equally effective whatever they shoot at. How is it that my naval ship's weapons can be improved to be more effective against naval units, but will not at the same time be effective against land units and cities. Are the only weapons torpedoes and depth charges? How is it that my air units improved against land units aren't also improved against other planes. Don't the missiles they carry do more damage to both? I know some missiles are specialized to track heat, but I suspect they can carry both types.