AI psychology: a thread attempting to analyze it´s behavior (contribs. welcome)

[caravel]

To start it: some things I´ve noticed

- When a faction starts to get pushed in one front but is still strong in the other, they´ll make an attempt at hacking at their other neighbour´s borders, if they think they´re weak, to get adittional breathing space. If you´re strong and already at war, and they are getting pummeled, they´ll immediatedly sue for peace

The AI is a simple beast but it appears to work like you say which is good enough and adds to the immersion factor. What usually occurs is, that the AI get's beaten and loses provinces, this produces larger stacks coming together in the backwater provinces. The AI then simply checks it's neighbours forces against it's own bloated stacks and invades them. This is why a reappearing faction has a tendency to spread out quickly. Large stacks mean that it can divide them up and use them for multiple invasions. I have often turned my faction over to AI control to see what it does with my forces. In most cases it will quickly spread out and conquer half of the map, then due to being spread to thinly it's empire will fall apart and be absorbed by a reappearing faction, and so the cycle begins anew.

- Low influence and risks of civil war induce warlords to sue for peace.

I've never noticed this in MTW much, in STW yes, but you could very well be right, possibly it occurs though to a lesser degree.

- Bankrupcy and large armies induce warlords to hack at neighbours' provinces (tested by seeing how the computer attacked and then refused to ransom a crown prince and other 200 high rate units)

I think this applies to your first point. Bankruptcy is just a result of high support costs in provinces incapable of supporting those units. The AI will eventually break out and attempt an invasion if it perceives it's neighbour to be weaker. The Aragonese will pretty much always try on an invasion of Tolouse eventually, if the garrison there is too weak. The same goes for the Danes with regard to Saxony. This is because they will eventually stock up with a lot of Royal Knights (causing bankruptcy) and when checking the overall power of their army and their neighbours they will find theirs to be superior. The AI doesn't go on numbers alone, but on the general and class and valour of the units defending the province. The AI must work out it's invasion probability from these factors. I have often found that the AI attacks my provinces the following year that I've moved a high command general or an elite unit out.

- Royal marriages are easier to get if the target princess is getting moldy.
Likewise, wars handicap your diplomatic attempts at RMs and alliances.

Another one I've never noticed, though I don't see why it couldn't work like that.

- As always, an undefended province is always a tempting target for enemies. Don´t forget to protect your soft underbelly and cover coasts with fleets.

An undefended province is always a target but there is an overriding factor and that is whether the AI wants the province or not. I have tested abandoning provinces to my enemies and allies alike, and and found that the AI often ignores them for years. In fact on many occasions they only attacked after the province had rebelled. I have yet to understand why this occurs, but it appears that the A goes for certain provinces and ignores others, it doesn't simply try to take everything indiscriminately.

- The enemy seldom uses spies, but it will often use assasins.

True, though this is mainly due to the higher building requirements for spies. Also, the AI is not effective in their use in that it cannot carry out any of the subterfuge missions. The AI can only move spies around and leave them in provinces. I have often seen the AI train about 5 spies and then simply leave them in that province for the duration of the campaign. In another case the AI trained the spies in Greece and then moved them to Serbia, and no further. They remained there for the duration.

- Low loyalty means cheap bribe prices. The computer does not bribe too often, not enemies, at least, but it does hit on cheap unit stacks from time to time. Specially rebels (as everyone does).

It seems to be the case. The lower the loyalty the cheaper the bribe. Rebel stacks appear to be cheap simply because most rebel generals have 0 loyalty.

- Peculiar Egyptian-Turkish-Byzantine relations:
-Turkey and Byzantium will almost always get to war. Particular detonating points are bankrupcy(as stated above) and apparently getting close to GH emergence. This war can be prevented if you marry off a Byz princess to a turkish prince

- Egypt is Byzantium´s staunch ally. Unless you hold lesser armenia or other common frontier, in which case it will strike again and again, even if they´re the losers for influence loss. So, if you want to trade, it´s a good idea to keep the turks alive, even if you kick them out of Anatolia and Rumelia.

AI Turks and Byzantines will almost always go to war yes. Again bankruptcy is a symptom of the AI having used all of it's resources to spam large stacks. It will then "vent" those stacks into surrounding provinces. As the player playing as the Turkish/early you can avert War with the Byzantine fairly easily, by simply not attacking them. They will usualy not ally with you however. The Egyptians on the other hand will ally with you, but will always invade Syria at some point early on. It is only when the Turks are out of the picture that the Byzantine and Egyptians will start on each other. I believe this occurs due to the AI "choosing" it's allies and enemies from among it's neighbours. It would be interesting to edit the startpos file and switch the Egyptians and Turks to each other's provinces and see if that changes the Byzantine attitude to them, I feel it would and that the Byzabntine and Turks are hostile simply due of the number of shared borders (Lesser Armenia/Rum, Anatolia/Rum, Trebizond/Rum, Georgia/Armenia, Trebizond/Armenia), many more than the Egyptians share with the Byzantine (Lesser Armenia/Antioch) and more than the Egyptians share with the Turks (Syria/Arabia, Syria/Antioch, Syria/Tripoli, Syria/Palestine). So (IIRC) the Egyptians share 4 borders with the Turks, the Turks share 5 borders with the Byzantines whom only share 1 border with the Egyptians.

We can apply this to other factions that share many borders such as the English and French, the French and HRE and the HRE and Hungarians. All of these factions seem to end up at war with each other.

-Peculiar Golden Horde behavior:
They always let crusades through

Not always, it depends on allied/neutral/war status. The AI will check the crusade against it's army stack in the province to see if it can win. I've ha similar problems with the Byzantine blocking my crusades for no apparent reason. It seems that if your crusade is perceived to be weak and your faction is not allied then it increases the chances of this occurring, when passing through pagan or orthodox lands.

- My theory on the "War Pope": it is triggered by papal bankrupcy and/or utter vulnerability of lands. Once playing Byz the pope attacked and suffered a horrible defeat in my newly conçuered Naples. They sued for peace the following year

I've never understood the papacy, but they do use use a different AI script I believe so it may be that they're programmed to try and provoke the player into wiping them out. It seems that way sometimes.