I have been researching this anyway. In the course of things, I found some of the logic the AI is supposed to use to generate Richmond interest.
In the event file "1861 CSA AI.sct" there is the following event.
SelectFaction = CSA
SelectRegion = $Richmond_VA
StartEvent = evt_nam_CSA_LowerAggressivityMidAtlantic61_AI_ON|1|0|NULL|NULL|$Richmond_VA|NULL
CheckAILevel = 1
MinDate = 1861/05/01
MaxDate = 1861/12/31
EvalRgnOwned = $Prince_George_MD;NOT
AI.SetAggro = $Mid_Atlantic;75;
NULL = NULL
AI.SetLocalInterest = $Prince_George_MD;50;
AI.SetLocalInterest = $Baltimore_MD;50;
AI.SetLocalInterest = $Wayne_Flat_WV;50;
AI.SetLocalInterest = $Westmoreland_PA;25;
AI.SetLocalInterest = $Philadelphia_PA;25;
NULL = NULL
AI.SetLocalInterest = $Fauquier_VA;200;
AI.SetLocalInterest = $Richmond_VA;150;
I'll assume some of you aren't familiar with the commands used. That event checks that three conditions are true:
1. CSA is being played by the AI.
2. The game date is between 05/01/1861-12/31/1861.
3. Washington DC region is not owned by the CSA.
Those aren't foolproof conditions, but they'll almost always work that early in the game.
If all three are true, the following things are set for the AI.
1. Stance (offensive-defensive) for the CSA is modified to 75 in the "Mid_Atlantic" area. According to the wiki page for that command, "A value > 100 is 'above normal', a value < 100 is 'below normal'". Mid_Atlantic is Virginia, but also New York, New Jersey, Pennsylvania, Delaware and Maryland. So any AI CSA forces in those areas should tend toward defensive postures.
2. A series of commands are given for several cities to set their interest for the AI. Among these, Richmond is only the second highest, after Manassas. I can see the logic behind some of the others, but I'm puzzled by Wayne Flat, WV; it's adjacent to Prestonburg, KY, and other than guarding that avenue to KY has nothing else of interest I'm aware of.
The following is from the wiki page of AI.SetLocalInterest:
"General Note: The value of a region depends of a dozen of factors, among them the structures types
and level, supply level, number of land links, Military control, part of a patch of controlled
regions (or isolated one), loyalty, Strategic City or Objective City tags and more...
The most important parameter: is the region a strategic city/objective?
A region of almost no interest can have a 2, while a coastal region with a mid-sized town and
harbor can get a 30 and the same but if defined as an objective can soar to 200!"
As defined by the April '61 scenario, Richmond is given an objective value of 10, twice as high as the next highest objectives. Richmond is also defined as a strategic city, which means it gives 1 VP per turn for holding it. As a result, Richmond, or rather the avenues by which Richmond is reached, should have a much higher value than other regions. The AI.SetLocalInterest command can be set as high as 999, so you could tinker with that value and see what it gets you. AI.SetLocalInterest is just for regions. There's a separate command for areas (groups of regions or other areas), AI.SetAreaLocalInterest, than can be used to set AI interest in such things as states.
A couple of things to note. I believe AI.SetLocalInterest and AI.SetAreaLocalInterest are set-and-forget commands, meaning they aren't per-turn settings. Once you run AI.SetAreaLocalInterest, it stays at the value you specified until the command is invoked again, or if there's some other command that operates on the same value. The event only runs once, probably on 05/01/1861, and those values will remain the same throughout the campaign. There's nothing else scripted to adapt to changes on the board. For the CSA, Washington DC is always "AI.SetLocalInterest = $Prince_George_MD;50;", and it's objective value is half that of Richmond (but higher than any other objective besides New Orleans and Charleston). The full campaign seems to want to steer the AI towards Richmond or DC, depending on which faction it's using, and is never given instructions to adapt after it achieves those objectives. The commands setting AI interest stop running at the end of '62, and even earlier for the Union. Promotion events for generals run to the end of the scenario, but that's it. Stance never changes in the mid-Atlantic area (AI.SetAggro = $Mid_Atlantic;75;). If Virginia is ever lost, the chances that are lower that the AI will seek to aggressively reclaim it, relative to other areas.
grimjaw's verdict: game designer believes single-player game is won in the first two years, after DC or Richmond are taken; doesn't expend effort coding for other eventualities. Full 1861-1866 single-player campaign is simultaneously WAD *and* delivered to customers incomplete. It's entirely possible that something was developed but not published with the game. As there are a number of unused events and scripts that *were* included, however, I think it is unlikely.
The original poster mentioned lack of forces defending Richmond. There is an event in the same file I mentioned above that spawns a large number of (permanently locked) units at Richmond, but only under certain conditions.
SelectFaction = CSA
StartEvent = evt_nam_CSA_DefendCapital_AI61-62|1|0|NULL|NULL|NULL|NULL
MinDate = 1862/01/01
MaxDate = 1862/12/31
CheckAILevel = 1
SelectFaction = USA
SelectSubUnits = Area $Close_to_Richmond;FactionTags USA
EvalSubUnitCount = >=;70
As you can see, it only operates *after* 01/01/1862, and only for a calendar year. It's limited to detecting units in the area defined as "$Close_to_Richmond", which is the following regions:
Roughly, that's the regions immediately adjacent to Richmond amd from Fredericksburg down to the peninsula. Not Norfolk or Suffolk, though, leaving a backdoor corridor around the AI's response if you want to cut it off via North Carolina. If you want to take Richmond, you can game the system by doing it before or after 1862. The number of elements has to be equal to or greater than 70. If you launched a deep cavalry raid, up to three full AGE divisions (54 sub-units, if you include the leaders) wouldn't trigger the event.
The AI was never scripted to adapt past the end of '62, and the game in general was not scripted very well to adapt to changes on the board. In the game I am testing now as the CSA, I've held Alexandria, VA, with a large force for two months, but the event that spawns many Union brigades still loads them (locked) in Alexandria. 19th century paratroopers, who'd have thunk it?
Although the game does include emergency militia events to defend against incursions into states, it doesn't have any scripting to adapt to a moving front line. The CSA objectives and their weights are:
Nothing about that ever changes. The AI might have lost Arkansas and Mississippi, but St. Louis will always be a higher objective. I am trying to improve upon this but I have a dog and a job, neither of which pays me very much. Especially the dog.