I think I may have really hit on something here. I am sure we have all had the AI, particularly the Zulu, up and declare war for seemingly no reason. In my last couple of games I have started right next to the Zulu, which is normally a recipe for war until you ahve wiped them out. I had greater problem on the other side of my borders though, so I wanted to remain peaceful with the Zulu. Although MPPs are an easy way to accomplish this they come late in the game, and can get you involved in wars you do not want. So, after my cultural borders were secure, I signed a RoP aggreement with them. For a while, every twenty turns, they cancelled and I had to pay a couple more gold/turn to keep it. However, they stopped doing this after the third renegotiation. I have now made it into the late industrial age without having ever fought the Zulu. In fact, they are at times gracious. My point is that, if there is a civ that for whatever reason you really don't want to fight, simply keep a RoP agreement with them for all time. They will not break it, because of the huge reputation hit, unless someone offers them something ridiculous to war with you. Generally, an enemy looking for an ally against you, will find someone cheaper to bribe than a gracious civ with a RoP.