The AI is VERY aggressive, even on lower levels. They seem to fight wars just for the sake of fighting. When I sign MPPs, my allies are a large help in defeating the 'evil' civilization I am trying to conquer. Once, I was after the English because they had too much oil. I got the Japanese against them, and they ended up 2 of their 3 oil resources! Be careful what you wish for. Try turning on all victory conditions, especially if you're playing on the lower levels. It's pretty hard to lose on Cheiftain or Warlord anyway.