Artificial intelligence (AI) is the term used for the behavior of non-player countries.
AI-controlled countries are contrasted with human player-controlled countries. In a single-player game, only the player's own country is controlled by a human; all others fall under the management of the AI. In a multiplayer game, up to 12 countries (over the Internet) or 32 countries (over a LAN) are controlled by humans; the rest are controlled by the AI. The AI also manages all rebel forces on the map.
The AI must autonomously make decisions modeling the sort of behavior a human would undertake given a similar situation. Thus, the AI develops diplomatic biases and preferences, undertakes military actions and manages economic and technological development for all countries in the game (other than those controlled by humans) using a system of complex rules.
- Main article: Options
- When set to easy, the player will get various bonuses, and the AI reacts less harshly to player aggression and vulnerability.
- When set to normal, no nation will get bonuses.
- When set to hard, the AI will get various bonuses, and the AI will react more harshly to player aggression and vulnerability.
- Main article: Luck
Lucky nations is a setting changeable at game set-up. It grants the luck bonus to ten AI nations, depending on the setting, either a predetermined historical group or at random.
The AI and human each interact with the game mechanics in slightly different ways. According to Wiz, the AI developer, some of these 'cheats' are "crutches" to eventually be "eliminate[d]", while others are "more or less necessary for gameplay or performance reasons", such as in the case of the AI's extra diplomat, required because the AI only handles diplomacy monthly and will not consequently re-use diplomats as frequently as most human players.
The AI does not:
- Cheat with dice rolls, not even Lucky Nations. If you believe this to be the case, you are experiencing confirmation bias (i.e. you notice the times it rolls well a lot more than you notice the times you yourself do).
- Get extra manpower (except on Hard or Very Hard difficulty) or free units.
- Cheat at not getting native uprisings in colonies. The AI will always pick the Native Coexistence policy to prevent uprisings, but this is an option open to players as well. (In previous patches the AI did cheat in this regard.)
- Cheat with sieges.
- Cheat with fort maintenance costs. (It did cheat with maintenance of border forts in previous versions.)
AI mechanic handicaps
The AI does have a few mechanical advantages. These are mostly to prevent the AI from being handicapped too much by its design limitations, in particular in cases where the AI is simplified to keep it from overwhelming the CPU with the complexity and/or frequency of its decision making.
- AI does not get naval attrition (but it will not normally send fleets outside of supply range for long enough for it to become an issue).
- Armies seen by an enemy will be known by all enemy AIs, but will eventually be forgotten if it goes into fog of war. This is somewhat like the way human players can see a unit and guess where it is some time after it enters FoW.
- AI gets +1 diplomat that it reserves for non-maintained actions, because the diplomatic AI 'ticks' means that it can't do the recall-send strategy that players do with maintained diplomats.
- AI gets +1 free leader pool because it's not nearly as good as a human at planning out when it will need leaders and needs to keep them on hand always.
- AI gets significantly increased naval/army tradition from battles.
- Naval missions in Mare Nostrum have knowledge of enemy navies outside your view, to avoid frustrating behavior for the mission user.
- AI receives more horde unity from looting.
- AI has a very different setup in regards to diplomatic options since human-AI interaction often gives the human an advantage. For example (again according to Gnivom), AI can call allies as though promising land, but then not lose trust when it doesn't give it to them; however, it will still try to when possible
- AI has 25% higher colonization range.
- AI does not get call for peace (but will usually make peace before it would become a factor).
- AI takes attrition in a province only for a number of it's troops ignoring all other armies.
- AI doesn't have fow. Even thou Paradox claim that AI doesn't abuse it, you can see a reaction to your army movements when those shouldn't have been visible.
Human mechanic handicaps
- A human player cannot be inherited on monarch death, though they may still be integrated manually by their overlord.
- Certain instantly game-ending events (e.g. the events enforcing the Polish-Lithuanian Commonwealth and the Iberian Wedding) can't fire for a player.
Improvements over EUIII
- The AI is now more definitive, offering clear "Yes" or "No" answers versus the random-chance-based "Likely" or "Unlikely" sort of answers it would give in EU3. It also now tells a player in the diplomatic screen the reasoning behind why it would accept or reject a player request. Hovering over the screen will show the basis of the AI's decision-making process, allowing more transparency for players to understand why the AI is making certain decisions. This allows players to work towards improving relations with AI countries.
- The AI will offer less "spammy" illogical choices, and can offer more sophisticated options, such as selling off provinces.
- Attitudes towards various nations are now more readily transparent. You can more easily see if the AI considers you an ally, a rival, or a target for conquest. For instance, a nation can consider itself "Threatened" by another country. According to the tooltip for this attitude, "X views Y as a threat to their independence. They will seek to ally with them for their own safety, but may seek strong allies elsewhere if this fails." One particular attitude, Outraged, can even drive a nation to form a coalition against the offending nation.
- War enthusiasm is a new mechanic to describe how much the AI country wants to stay in a war. On a range of 100 (very enthusiastic) to -100 (wanting to throw in the towel), you can now look at each enemy and ally to see how much fight they still have left in them. If an enemy has positive enthusiasm, they are less-likely to accept peace offerings at all, and will also reduce how much they are willing to part with in a peace deal. If they have a negative war enthusiasm, they will be more willing to part with concessions to achieve peace sooner rather than later.
- The AI is also more savvy to badly-structured peace offerings from players. It now has a better way to weight the concessions it wants, and is less likely to take poorly-structured peace offers from a player. Players can see this by seeing a green thumbs-up icon next to peace offerings that the AI values fully, a golden hand (palm-down) next to offerings the AI sees have some (but not full) value, and a red thumbs-down next to offerings the AI will consider unimportant or undesirable. For instance, a distant, landlocked province upon which it had no core would very likely be considered undesirable. A core province right on its border would be considered very desirable. And so on.
- Army management has also been improved. Smaller AI nations allied in a war will seek to gang up with larger forces to act in unison and follow the larger forces around, rather than be destroyed operating independently and in isolation. The AI also focuses on its objectives more now, to better achieve its wargoal. Lastly, the AI can also reserve some of its forces to act as "Hunter-Killer" armies. In EUIII, AI armies often settled into a siege and refused to move, even if there was (to a human eye), urgent events taking place nearby. Now, Hunter-Killer armies will seek out enemy armies and attempt to engage them in direct battle. They will also protect their own besieging forces, intercepting enemies and acting as defensive screen.