I've always tried for a peaceful victory throughout Settler to Diety level. It's OK under Prince, but from Prince, the AIs are likely to go war when I have no (or little) militiary units. First, they're friendly to me, and I accept all their trade, sometimes demands. But after some turn, they come Guarded, then Hostile and finally, WAR
.
However, I notice that they usually go war with me after I open border for them, and I tried some game, NEVER Open Border for them, and they NEVER go war with me, even I have no army at all. (Note: Sometimes at the early game, when my lands are small, all 2 Civs I met declared war on me in the same turn.)
So is it a good idea to avoid war?

However, I notice that they usually go war with me after I open border for them, and I tried some game, NEVER Open Border for them, and they NEVER go war with me, even I have no army at all. (Note: Sometimes at the early game, when my lands are small, all 2 Civs I met declared war on me in the same turn.)
So is it a good idea to avoid war?