After playing a few games in Europa Universalis 4, it seems to me that aggressive expansion penalty is a major obstacle in a military conquest style of game. Conquering a few provinces (especially with a high tax base?) gives a huge penalty. It doesn't seem to really depends on whether your own country is big or not.
Because the aggressive expansion penalty drops in a very slow pace over the years, this makes it impossible to expand quickly. Are there any strategies to minimise that?
Best Answer
You are indeed right that aggressive expansion (AE) is a major obstacle to military expansion: it is what brings balance to the game and allows smaller nations to become successful and beat much more powerful rivals. Otherwise, superpowers can grow unchecked which makes for rather uninteresting games.
At any rate, there are other ways to go:
Diplomatic vassalization. This is typically the preferred strategy bar none, if your regional situation allows it. You placate, bribe, ask, threaten your targets into accepting vassalization peacefully.
Preferably, most of the conditions below need to be fulfilled for it to be effective, or indeed possible:
The 190 reputation needed can be a challenge to build, particularly if you share a land border with them, but there are many ways to increase your standing with them. Diplomatic vassalization is only possible to propose to countries that have less than 40 total tax base (your own tax base needs to be significantly higher than theirs).
Military vassalization. Reserved for countries that just won't see eye to eye to you in terms of your global domination and need to be persuaded gently with a stick, shooting or other. Most of the restrictions applying to diplomatic vassalization are not applicable here: you can vassalize any sufficiently advanced country with any form of government or religion, provided they are small enough to have province score in a war less than 100%.
Some tips:
The diplomatic game can be much more satisfying and rewarding in EUIV, and can bring immense variety and depth to the game.
Further information with more strategic and tactical tips is available on EU4wiki: