Aggressive Expansion & Coalitions

This guide was created to help EU4 players understand how Aggressive Expansion & Coalition Mechanics.

There are three sections to this guide:
Introduction to Aggressive Expansion & Coalitions
This section explains what aggressive expansion and coalitions are, why they are important and why they are in the game.

Basic Overview
This section explains the basics that you need to know in order to enjoy playing the game

Facts & Figures
This section contains information that you don't need to know but if your a stat freak or like to play as efficiently as possible, then you may find this section useful.

Practical Conclusions
This section is all about putting the information you have learned into practice, giving some conclusions about how these mechanics should affect the way you play the game.

Introduction To Aggressive Expansion & Coalitions

Introduction To Aggressive Expansion & Coalitions
In this section I will talk about what Aggressive Expansion (AE), the role that it plays in EU4 and what you need to know to avoid disaster in your games.

Aggressive Expansion or 'AE' is a mechanic that paradox has created in order to slow the expansion of nations and affect your diplomatic relationship with neighbouring countries.

The first thing that you need to know about AE is that it is not a global variable that affects your relations with every nation in the same way and to the same degree. Aggressive expansion is calculated dynamically on a per nation basis.

What does this mean?
Basically the actions that you take will affect some nations more than others depending on a number of rules which I'll go into later.

Why should you care about Aggressive Expansion?
Aggressive Expansion acts as a negative modifier to your relations with other nations, it will slowly lower a nation's opinion of you until they begin to hate you or even become your enemy.

In addition to the relations modifier it can have an immediate and more devastating effect, the creation of a coalition.

What is a Coalition?
A coalition is group of nations who have decided that you are being too aggressive and need to apposed on a large scale. Declaring war on a nation who is in a coalition against you bring every member of the coalition into the war. Likewise if any member of the coalition declares war upon you, all of the coalition's members will join the war against you.
You cannot negotiate individually with members of a coalition, you may only discuss peace with the war leader, which limits what you can demand in a peacedeal.

For these reasons it is essential that you avoid gaining too much aggressive expansion with a nation.

Must Know Stuff!

Ok so lets get down to the facts and what you need to know.

Aggressive expansion decreases your relations over time with other nations and if it goes above 50 with a nation, there is a chance that they will join a coalition against you.

Aggressive expansion is cumulative, which means that if you gain aggressive expansion in two separate wars it will be added together.

Aggressive expansion decreases over time and the rate at which it decreases can be affected by ideas or advisors that give bonuses to 'Better Relations Over Time'.

The primary way that aggressive expansion is gained is through demanding territory or vassals in a peace deal. However it can also be gained through being discovered whilst carrying out a covert action against a nation such as fabricating a claim.

You can check the amount of aggressive expansion that you have with another nation using the 'Opinion Mapmode'. As shown in the image below, you simply hover your mouse cursor over a nation and it will show you how much aggressive expansion you have with them.


In the above image you can see that the country I am playing has 26 aggressive expansion with Bosnia and that it is decreasing by 2, every year. This means that my relations with Bosnia are being decreased by 26 per year because of my aggressive expansion with them.

Perhaps the most important thing to check when creating a peace deal is how much aggressive expansion you will gain for your demands. Which countries will be affected and by how much?

In the peace panel there is a section that displays the average aggressive expansion that will be gained. This number is very deceptive and fairly useless. Hovering over the number, with your mouse cursor, however will reveal far more useful information.


In the image above you can see that I will gain between 2 and 50 AE with 120 nations. You can also see that, by making this peace deal, 3 countries will be pushed over the 50 AE minimum required to join a coalition. This doesn't mean that they will definitely join the coalition, as they may decide its not in their interest to join, but unless you are a very powerful nation it is likely that they will join a coalition against you.

The amount of aggressive expansion that you gain with individual nations depends on a number of factors:

Location
The further away a nation's borders are from the victim of your aggressive expansion, the less AE they will gain against you.
The amount of AE acquired is also affected but the region or continent that the victim is on. Nations on the same continent or in the same region as the victim will take more aggressive expansion than those who are not.

Religion
If the victim of your aggressive expansion is not the same religion as a nation, said nation will take gain less AE against you.

Holy Roman Empire
Members of the HRE gain double the normal amount of AE if another HRE member is the victim.

Relationship to Aggressor
If a nation is an ally or subject of the you then it will gain a lot less AE against you.

Facts & Figures

Base Causes of Aggression Expansion

• Annexing provinces costs 2 AE per base tax
  
• Force vassalizations cost 1.5 AE for each base tax of the nation
  
• Fabricating claims costs 2.5 AE if caught
  
• Justifying a trade conflict costs 2.5 if caught
  
• Declaring war without a casus belli costs 20 AE
  
• Breaking a truce costs 50 AE

These costs are moddified by the following:

• If a war target is an HRE member then other HRE nations gain 100% more AE against you
  
• If a war target is not a co-belligerent the AE you gain will be increased by 50%

Unfortunately we don't have data on the other modifiers so I haven't listed them here.

For each point of prestige that you have, the amount of AE you gain is reduced by 0.1%.

Nations with at least 50% AE are likely to join a coalition against you.

You can have a maximum of 1000AE with any one nation.

Practical Conclusions

Here are some conclusions that you can draw from this guide.

Large nations are able to grow much faster due to the distance and region modifiers for the amount of AE that nations take against you.

Check the amount of AE you have with nations in the target area you wish to expand in before declaring war.

If your aggressive expansion is too high to take more land in an area, try expanding in a different region or part of the world.

As a general rule coalitions should be avoided wherever possible, not only are they dangerous but this also make expansion much harder due to widespread truces.

Just because a nation has more than 50 AE against you, doesn't mean they will definitely join a coalition. It depends on a number of factors including your strength relative to theirs and the coalition's strength.

Nations CANNOT join a coalition if they have less than 50 AE against you.

[Timey Wimey]

a little bit useful (づ ●─● )づ

[Sumnomobum]

just a number

[› Cyfer]

You should probably add that the base AE has a multiplier based on opinion. So the amount of AE you take is reduced if they like you and compounded if they hate you. Improving relations before you take AE is the best way to reduce it, an ounce of prevention is worth a pound of cure and all that jazz.

[legacyadrian2.0]

Nice

[beagels01]

Obvious, no helpful information. No limits of AE/relations for joining coalitions, not even the basic one of 50/-1.

[Hattarik]

Once AE goes below fifty they are forced to leave.

[Beefybananas]

what is the threshold for members of a coalition leaving the coalition?

[Wat]

the coalition will disolve eventualy ?

[I Major Dave I]

Otherwise nice guide :)

[I Major Dave I]

A -26 AE modifier does not cause -26 relations degredation per year. It's just -26 to relations.