I am playing a game (first Prince level game, large Continents, I'm Catherine) where I am on the same continent with Montezuma, Gengis Kahn and Alexander. I was the only one to found a relgion, and my religion quickly spread to all the other civilizations. I also actively traded with each one, and had at best a +15 rating with Kahn, and +13 with Monte & Alexander. Monte was a little lower because he was in a war with Kahn, and I refused to aid him. Alexander was low because I refused to give him tribute. Well, at about 1600, just after the "most powerful civilization" rankings came out (Alexander #2, me #6 out of 7), Alexander declared war on me. Strange that a nation that can be so friendly for so long, and have such good relations would all of a sudden declare war on their neighbour. Fortunatley they're still pumping out elephants and macemen while I've got grenediers & cossacks, but I'm just ramping up my military and he's already there... Gonna be a tough fight!