I posted a thread 2 months ago about this here, and hoped that will be fixed since it's the worst mechanic of this game.

I'm explaining :

The light green IA declares war on dark green IA, weakend becauses it loses a war against me a little while ago.

But they seem to be as weak as each other, and light green never won a battle against dark green.

So I decided to take advantage of the situation, I declared war on dark green too.

But here we are : dark green has only one city. If I take the city, it's the end of the war. If I wait, I lose my war support.

So let's take the city and see what happens.

End turn. Then :

AAARGH ! I've done all the job and light green takes the victory and vassalizes dark green !

Moreover, how can it have enough war score to vassalize it when it has done absolutely nothing ? 

Please, I need you to upvote this thread for developers to realize that this is so annoying.

We want to be able to take advantage of the weakness of our enemy already at war, and not give a free victory to an opponent.

On my previous thread (link at the top of the page) I have proposed some answers to improve this kind of situation, please feel free to upvote this one too.

Regards.

Le Bambi Kriska