i almost never had A.I declare war on me, i usually try to pin the most powerful civilization in the game against every other lesser civilizations in the game so that they won't bother me as i try develop my planets. but i think the peace making is as the previous posters suggest, has to do with the military rating and the current war that they have with other A.I. crazy as it may sounds, if you utterly obliterate all A.I's ship, and offer them peace treaty with some of your latest ship, they will give you everything. i mean everything as in everything. including themselve, their wife, their children, their women, their relative, every single thing. i tried that on several civilization in obscene mode, they think that's a great deal, it has to be. because none of them ever declined.