IMHO, however, the best existing strategic-level combat model that I know of is the "Command HQ" model for its elegance and simplicity.

In the CHQ model, you have combat units with MPs (movement points), HPs (hit points) and FP (firepower) just like Civ2 units. However, there are some crucial differences.

1. CHQ combat is NOT to the death. When you launch an attack you would only weaken the enemy by your FP. Therefore a few turns may be needed to kill an enemy unit. If your unit was mobile you could try to retreat even if attacked first.

2. CHQ combat uses a finer grid. Therefore units can NOT be stacked directly on top of one another. Instead, "stacks" are formed by putting units on top of each other but offset by about 1/3 of the space of a whole unit.

3. All land and sea units can only attack other units in direct contact with it, however, each unit can be directed to attack exactly one other unit during any given turn. Of course this means that you could direct, say, 5 units to attack one unit at once to concentrate your FP for a turn.

4. All air attacks are abstracted. You do not actually move aircraft when attacking but simply pick a target unit to attack within range which could either fail or succeed (or your air unit could be shot down if enemy has anti-aircraft unit in range).

The CHQ model is very simple and easy to implement and eliminates many complaints/defects of the Civ1/Civ2 model. Namely:

1. Aircraft blocking land units "bug" - Since aircraft attacks are abstracted and no actual aircraft moves outside of cities/bases, you can't use aircraft to block land units like in Civ1/Civ2. (Also eliminates having to track MPs for refueling since you are not allowed to attack outside of range.)

2. Land units blocking aircraft "bug" - Since aircraft movement and attack is abstracted (similar to the airlift of Civ2), land units can never block the movement of aircraft like the case of Civ1/Civ2 (In Civ1/Civ2 you HAD to attack any land units in the way). Of course, this doesn't mean that your aircraft can't be shot down. If you have sufficient hostile anti-aircraft units in range, there is a chance of being shot down every time you attack/move aircraft.

3. Stacking problems eliminated - Each land tile subdivision can hold one and only one unit and attacks are directed. No more confusion as to who attacks and who defends during stack vs stack attacks because in essence there are no true stacks and each attack is either one-to-one or many-to-one and this is entirely controlled by the player.

Of course, to use the CHQ combat model, a finer grid is needed. I propose that each land tile therefore be sub-divided into 9 sub-tiles and a maximum of 9 units per land tile. Sub-tiles however only come into play during combat. (Another way of putting it is that there are two levels of grids).

For Civ3, I hope that a modified version of the CHQ model is used as it is
vastly superior to the Civ1/Civ2 model. (The air combat is definitely much much better!)