Prediction of winning a war by AI

[Dustman]

How does AI calculate its chances?

Just been DoWed by a neighbor while playing IP with Defensive Wars Only. My huge navy of 9 ships quadrupled in less than an year, leaving AI inferior in fleet power. As a nice finisher, we got only one entry point and its blocked by my starhold with 3.2k power, bigger than power of my all whopping 40 corvettes combined.

Can't really see how AI planned on conducting attack even it was just a starport bastion. Not like I complain about possibility to claim something and get some slaves, but designer's logic on when to declare doesn't hit me.

 

[beckermt]

Largely just a direct comparison of fleet power, economic power, etc. The AI doesn't know how much of what you're stockpiling and doesn't assess specific systems. In addition, I don't believe static defenses are accounted for at all. The baseline assumption being that said defenses are speed bumps, but not unassailable.

 

[Kami-sama]

Here are the mechanics behind declaring war:

First, the AI will decide if it can declare war on someone. The requirements are to use 50% of their Naval Capacity and have at least 6 attack armies.

Second, the AI will decide if it wants to declare war on someone. That is determined by their AI personality, the AI Aggressiveness setting you picked at game creation and whether they can expand or not. They're twice more likely to want war if they can't expand into systems with habitable planets and 4 times more likely to want war if they can't expand at all. Hive Minds and Driven Assimilators are 10 times more likely to want war when they can't expand.

Finally, the AI will decide if the war is worth it. For this they compare the Relative Power of both empires and then decide whether to declare war or not based on their Bravery, which is determined by their AI personality. I wrote the bravery modifier of every AI personality here: https://stellaris.paradoxwikis.com/AI_personalities. For example the Honorbound Warriors are willing to declare war on an empire stronger than theirs while the Slaving Despots will only declare wars on empires with twice less Relative Power than them.

 

[beckermt]

Here are the mechanics behind declaring war:

First, the AI will decide if it can declare war on someone. The requirements are to use 50% of their Naval Capacity and have at least 6 attack armies.

Second, the AI will decide if it wants to declare war on someone. That is determined by their AI personality, the AI Aggressiveness setting you picked at game creation and whether they can expand or not. They're twice more likely to want war if they can't expand into systems with habitable planets and 4 times more likely to want war if they can't expand at all. Hive Minds and Driven Assimilators are 10 times more likely to want war when they can't expand.

Finally, the AI will decide if the war is worth it. For this they compare the Relative Power of both empires and then decide whether to declare war or not based on their Bravery, which is determined by their AI personality. I wrote the bravery modifier of every AI personality here: https://stellaris.paradoxwikis.com/AI_personalities. For example the Honorbound Warriors are willing to declare war on an empire stronger than theirs while the Slaving Despots will only declare wars on empires with twice less Relative Power than them.

How does diplomatic relation/opinion play into the decision?

 

[Kami-sama]

How does diplomatic relation/opinion play into the decision?

https://stellaris.paradoxwikis.com/Diplomacy#Attitude

The AI will only consider declaring war towards empires they hold an Attitude that does not prefer peace towards.

 

[Dustman]

Static defenses early game are not just speed bumps. They more or less turn into ones later on, especially with jump drives, but in first 40 years or so can be crucial. Not like unassailable for a determined attacker, but a place where losses are anticipated. Quite bad AI can't take it into account when calculating probably invasion routes.

Anyway, the war I mentioned went very uneventful for first few year, not even a single fleet showing close to my borders. Later I simply claimed and grabbed their homeworld but original idea of war declaration was rather stupid.

 

[beckermt]

Static defenses early game are not just speed bumps. They more or less turn into ones later on, especially with jump drives, but in first 40 years or so can be crucial. Not like unassailable for a determined attacker, but a place where losses are anticipated. Quite bad AI can't take it into account when calculating probably invasion routes.

Note that that was simply an assertion on my part. It's possible that the AI takes static defenses into account.

 

[Arutar]

Static defenses early game are not just speed bumps.

Agreed. Also, often people forget that loosing defense stations does not contribute towards war exhaustion. In early game, in particular on grand Admiral, static defenses can be the key to victory.

 

[Foefaller]

Note that that was simply an assertion on my part. It's possible that the AI takes static defenses into account.

They take it account in that they will try to avoid them for soft targets if they can, but as far as whether to declare war to start with AFAIK they don't, since it is not considered for your relative military power.