High alert (but this will probably need another name): unit gets +100% bonus. Drawbacks- must be entered when unit has not moved at all (must have full movement available) and requires an extra shield to support while on high alert. Units on high alert can only stay on high alert for one turn, and after revert to alert status. Units will have to return to a city with a barracks/airfield/whatever in order to be at this status again.

Alert: +75%, but costs two shields to support. Permanent, and will stay until the unit is reassigned to other duties.

Counter attack: no defensive bonus. However, the fist unit that moves into range of this unit is attacked (so if artillery 2 squares, others 1 square). This be like an opportunity fire, where a unit would wait at an outpost and attack the first unit it sees. The unit (if it is not destroyed) can be available to move on the next turn. Units told to counter attack could make attacking fortified areas a lot harder if the enemy knows that your coming...

Fortify: units build a fortress terrain improvement, taking twice as long as normal. The fortress will remain after the unit moves away. Unit receives a 25% PENALTY while building terrain improvements. Also, the unit could be told to build an airfield or sensor array (or the CIV 3 equivalent).

Defend: normal CIV 2 'fortify': +50%.

All units that have movement points available, have higher attacks than defense, are at full strength, and are ordered to 'space bar' immediately revert to counter attack status.

All units that have movement points available, have higher defenses than attacks, and are ordered to 'space bar' immediately revert to defend status.

Then again, having all those commands could also be good because it would allow AI civs who would play very differently...

Why would you allow high-alert only for one turn? The overuse of this command is already prohibited throught the +1 shield support.

I would just like to see

hold ground stance, fortify from civ2, no building of bases unless unit has ability to like legions

defcon4 stance, maybe red alert something catchy, +1 shield or +100% support, +100% unit attack/defense.

counter strike enabled, units go after attackers or premptive strikes should be dangerous if they run into a stack with fortified units.

Units could be on normal or one of these, each has an impact or cost could add some to tactics like hit and run tactics or something.

(civ A is defined as the civ that will be defending (or counter attacking), civ B is the one that will attack)

Case 1: the civ B into range is a clear attack unit. This would mean that the computer knows that if the civ B unit attacks, it would destroy the strongest civ A defender. No thinking involved. The AI should quickly tell civ B to counter-attack and waste civ A's unit.

Case 2: civ B's unit that comes into range is a clear attack unit, but has a high defence. If civ A's possible counter-attacking unit can defeat the enemy unit without taking more than 75% (or some user-customizable amount) of damage, then the unit attacks. However, the problem occurs when civ B's unit can defeat the strongest defensive one of civ A. Then, the computer looks at the odds of counter attacking, and the possible damage that could be done to civ B's unit. If the damage done to civ B makes the civ B unit unable to defeat the civ A unit, then the attack is ordered. If not, then the counter attacking unit of civ A is told to wait, and the defensive unit from civ A is destroyed.

Case 3: the civ B unit that moves into range is a defensive unit, meaning that it has a higher defence then attack. Civ A will not counter attack, but instead reserve troops for much more threatening situations. The defensive unit that moves up first could be considered to be 'covering' the attacking units that pull up later. It will defend the square when civ B's attacking unit pulls up later

Case 4: the civ B unit is considered a scout type (low attack and defence), caravan, or engineer. The unit will be attacked at beginning of Civ A's turn, if any counter attacking units can still attack. It will not be attacked immediately.

Case 5: the city being defended has a wonder, is the last city, or is a capital. Special rules will apply here, depending on how much the player values the city.

Important: units will counter attack as long as they have movement points. This will only occur as long as their chances of success are high, or the civ A city is considered very important (case 5).