AI guarantees independence of nations after taking their territory

Question

I've noticed that sometimes when an AI nation A takes a large percentage of another AI nation B's provinces, they guarantee their independence. Is this an inbuilt strategy from the EU4's AI to prevent other nations from taking advantage of the B's temporary military weakness?

If true, could this be a viable strategy for a human player?

Answer 1

I sometimes do use this strategy. I see the following + points for it:

• If I want to take more of the weakened nation's territory later, I don't want it to be taken by another large nation in the mean time. This is especially true if that other nation happens to be a member of the HRE;
• Sometimes I want to be in a war with a neighbour counrty or rival, but I might have a truce with them or be unable to declare war on them because of their strong alliances or HRE membership. Declaring guarantees on the nations they want to attack can get me into a defensive war against them. Please be careful to think about this option, because the AI will most likely attack when you are otherwise engaged and the timing of the defensive war may not be to your liking.

There is however also a major drawback. When you revoke the guarantee there's an automatic truce, preventing you from declaring war right away. This delay is often just the window of opportunity for that close by rival to launch the attack you wanted to prevent. It is therefor essential that you time the withdrawal of the guarantee well.