At what levels do the AI cheat and how?

[Solomwi]

Yes, it was the day that will live in infamy
That was their last act of foreign agression, though

Good work, then.

The Russians did the same to me once after I had been nice enough to let their puny little backwater nation come back through my territory from barb hunting in the north, so I took Las Vegas back and annexed them. Russia will never survive another game I play.

[Catt]

I flipped a city at Demi-God recently (v1.15b) and got one free regular defender. Has always been so, to my knowledge.

The "leave or declare war" is not quite so straightforward. A poster named TheNiceOne did a study of it at CFC, and the "leave or declare war" option comes when a threshhold is met -- that threshhold takes into account the nature of the interloping unit(s) (military or not), the proximity to cities, and the length of stay. A settler-spear combo can move through territory for some time, particularly if it stays away from cities, without a "declare war" option. A scout can stay in territory for a long time, even close to a city. A stack of archers will generate a "leave or declare" quickly. His tests showed that the threshhold test is the same for human or AI.

The AI does get the opportunity to rush a unit in the "same turn" due to the way turns work. Turns move through four phases: human production; AI production; human unit move; AI unit move. In this context, the AI takes a human city (or flips it), and rushes a unit build. After the AI is done moving units, the turn cycles through the human production phase and then the AI production phase -- the rushed unit is produced during the AI production phase. Only then does the human get to move units (and try to retake the city) -- lo and behold, the AI's rushed defender is already in place. The human doesn't get this opportunity because the AI always moves last -- the human can take a city and rush a unit, but the rushed unit isn't completed until the next human production phase, which comes after the AI gets to move units (and may have tried to retake the city).

BTW, there is a human advantage to the turn system, too. Since the human production always precedes the AI production, any time you get to "1 turn" on a wonder and then get to move your units (without an AI wonder pop-up intervening), you know the wonder is yours without question. This could have pretty drastic consequences particularly in the context of great leaders (less so with SGLS in C3C). If you and the AI each get an SGL on the same turn and each use it to rush the same wonder, you get the wonder and the AI gets a very expensive city improvement. In fact, any time the human gets an SGL he/she is assured of building the wonder of his choice -- human production always precedes AI production.

I'm not sure about the AI never asking another to remove its troops. I thought that it did occur.

Catt

[ErikM]

Very nice explanation Catt

I *almost* certain that I did not get a defensive unit on Deity when an enemy city flipped to me, but maybe I was wrong. Or maybe it is something like you only get a freebie if AI has at least one unit in the city.

Culture flips are so rare on Demi+ though that this point is rather academic. Rather, you have to worry that your own cities do not flip

[Catt]

Originally posted by ErikM
Culture flips are so rare on Demi+ though that this point is rather academic. Rather, you have to worry that your own cities do not flip

Yup (my flip occured with an AI city recently conquered by a distant civ, shortly after I relocated my palace very near the city -- can't remember more than one or two other flips in my favor in the last several months)

Catt

[Solomwi]

Leave it to Catt to step in as the voice of authority and reason.

On the asking to leave bit, I was arguing from the premise that it was a developer-documented aspect of the game that AI would not ask another AI to leave, since my first reaction was "Well, how would we know?". Granted we'd know that the AI does, at times, allow movement through its territory to other AI's, but not enough to say always and never. Catt, now that you've cast a bit of doubt on that, I'm curious.

[Catt]

Originally posted by Solomwi
On the asking to leave bit, I was arguing from the premise that it was a developer-documented aspect of the game that AI would not ask another AI to leave, since my first reaction was "Well, how would we know?". Granted we'd know that the AI does, at times, allow movement through its territory to other AI's, but not enough to say always and never. Catt, now that you've cast a bit of doubt on that, I'm curious.

I haven't reviewed TheNiceOne's thread, but I'm pretty sure it didn't address whether AIs make "leave" demands on other AIs -- what it did address was that the "point system" for triggering the "leave or declare" threat was the same whether the interloper was AI or human (i.e., a human settler-spear combo could move through AI territory in the same manner as an AI combo could through human territory). Don't recall any developer statements on the issue.

It's also been awhile since I ran a debug game (which would show AI units being expelled). Many human expulsions happen in the early game when we're unlikely to have views around AI borders to see AI-AI expulsions. Many others occur when, as ErikM posted, Civ X moves through Civ Y's territory to attack Civ Z. AI's very often have RoPs with each other, so no "leave or declare" occurs. But I don't doubt (heck, I just witnessed it in my last game) that an AI will move numerous military units through another AI's territory without an RoP to attack another civ. My own doubt about "never" arises because perhaps the AI "trespassed-upon" won't ever ask a stronger AI foe to leave or declare, knowing that the foe will declare (but might do so when it knows the other AI will leave, and we just never see it happen). I just know that there are times when an AI will move large numbers of units through another AI's territory without an RoP, and I've never been successful in doing the same thing.

Catt

[Solomwi]

I've been on the receiving end of Civ Z's dribble of units attempting to impersonate an invasion force before, so please don't think I was denying that the AI will let other AI through its territory without an ROP. Until I read Erik's post, I was under the same impression, that the AI just deferred to stronger AI's and asked weaker AI's to leave, but decided to give the benefit of the doubt in case there had been a developer statement.

[Catt]

Originally posted by Solomwi
I've been on the receiving end of Civ Z's dribble of units attempting to impersonate an invasion force before, so please don't think I was denying that the AI will let other AI through its territory without an ROP.

I didn't think that -- ErikM's post just highlighted for me that I don't have any clear memory of evidence of an AI-AI expulsion, while I do have a clear memory of a failure to expel in circumstances that would clearly trigger the "leave or declare" option between AI civs. The option could still be there, of course, and weak AIs aren't availing themselves of it or the option triggers a war declaration without us knowing of the reason why or the AIs really won't use the option on other AIs.

Catt

[vmxa1]

Right after I left my last post on this thread, I flipped a city and got a spear. So that is what I had always seen. Flips are very rare in my games for either side.

[Aeson]

Flips you get the unit.

The change was in gifted cities you don't get a unit, while IIRC the AI does (could be the production cycle thing though).

[LzPrst]

I feel the AI should be more "protective" of its territory, after all another civ can just march in saying we're just passing through, or else... and then charge right into the capital or whatever. of course the AI isnt smart enough to do that, but I think the AI would be better if it "played" like if it was playing against an "intelligent" opponent.

[vmxa1]

I don't see the problem with the AI letting units pass through. I do it all the time. If you are playing at a level where the AI has many free units, you do not demand they leave, when you are sure they are after someone else.

You can end up with the AI fighting on your land. It is not pleasant, but you have no real choice. The AI should be able to behave that way and it does at times.