When your alliance presently makes a truce with a warring alliance, you cannot attack them. This is good! But, one easy exploit is to make an unreasonable demand of someone in the enemy alliance. If a truce is agreed upon then then it should be more permenant than this to give the losing side some kind of recompense for what they have to give up in the deal (such as a system), and give them a chance to build back up.


One easy way to do this would be to enforce truce's for 30 turns, disabling diplomatic aggression which might lead the enemy alliance to re-declare war, and automatically imposing closed borders. As it is now there is literally no reason for a losing side to agree to a truce because the aggressor still has options to continue fighting the war, and the losing alliance is just giving things up to the enemy for free.