Relations are the overall quality of the diplomatic, religious, and economic ties between two countries. In EU2, the quality of relations between each pair of countries is quantified as an integer ranging from -200 to +200. Negative numbers indicate cold relationships; zero is completely neutral; positive numbers indicate good relations.
Effects of Relations
In general, diplomatic actions between countries with negative relations will be unsuccessful, whereas many actions require positive relations and the most powerful diplomatic actions are possible only when relations are sky-high (190+).
Here is a partial listing:
- AIs don't declare war on countries they have good relations with
- When one country annexes another, it gives a casus belli to all countries with relations of -150 or worse with it.
- Royal marriages won't succeed if relations are -150 or less, or between -5 to +25.
- +100 relations are required for mapswapping.
- +190 relations are required for diplomatic vassalization.
- +190 relations are required for diplomatic annexation.
Changes to Relations
Relations between countries are ever-changing. There are three main grouping of relationship changing events: automatic monthly adjustments, diplomatic action, and other.
Automatic Relations Changes
Each month, relations between countries are automatically adjusted based on several factors. Positive factors include:
Negative factors include:
- existing casus belli between countries (although this effect will be negated by a royal marriage between them)
- low current relations (-150 or lower)
- high badboy in either country
- religious intolerance of the other country's state religion
The details of how these factors affect relations is not known.
If the net relation change is positive, relations will increase between countries up to a limit that is set by their state religions. If these are the same, relations will increase up to +125, but not above. If different, the maximum is +25.
Relations Change via Diplomatic Actions
Many diplomatic actions will change relations. Here is a listing of the effects of diplomatic actions on relations:
- give gifts: random, generally better for big gifts.
- send insult: -50.
- declare war: -100.
- royal marriage: -5 on failure, +15 on success.
- offer peace: +50 if accepted.
- trade embargo: -25 to relations with embargoed country, -10 with its co-religionists.
- Diplomatic annexation: -30 if the attempt fails.
- Diplomatic vassalization: -30 if the attempt fails.
Note that AIs tend to send other AI countries gifts, but they never send them to the player. Thus, they tend to be able to keep up good relations with each other, whereas the player will find it difficult.
Other Causes of Relations Changes
Here are a few other causes of relations changing, from non-diplomatic actions:
- Changing state religion: -100 to all countries of old religion, +50 to all countries with new religion.
- Merchant competition: -5 when you bump a merchant from another country out of a center of trade.
- Annexation: -50 to relations between a human-played country annexing another, with all countries with the same state religion as the annexed country. There seems to be a much lesser hit for AIs.