I just went an entire game without fighting a single war. The strange thing is I never had an army, I only ever had my starting warrior. The AI had wars - I personally saw Spain and Inca fight it out and I saw Korea invade Sweden, taking a small town and destroying Stockholm's walls - but, despite really upsetting everyone bar the Incans to the point that I was being denounced constantly, they never declared war, even though I had only one warrior and only one city had ancient walls (which I built when Scotland had a charriot and a warrior suspiciously hanging around it's border), so only a mighty strength of 20 versus everyone else that had hundreds. I even shared a border with Korea, no idea why they attacked Sweden and not me.