Quote Originally Posted by Tristan de Castelreng
Each time you save/load to retry an agent mission (mostly due to failure... I presume), you'll have to reload the seed (that is to say the way that the AI generates the chances of success)...

In order to do that, you have to make the AI do another calculation, either by trying another agent mission, or fighting a battle...

That way, you should get a different result from the one you had earlier...
Not true, as far as I've tested so far. Reloading the game and doing nothing else (this is tested on assassination attempts) but the action in question will yield different results. To be absolutely sure I parked my assassins directly next to and facing the targets, so literally there was nothing done but the attempt itself. There was some interesting discussion in a few other threads on this.