Some people are troubled by the lack of aggression of the AI civs, and perhaps they aren't as aggressive as in the past. However, they aren't exactly pacificists. In the game I just lost, I was playing as the Poles on Emperor level. The Romans were my neighbors. I had two cities up and they were growing well. I was getting ready to build another settler. I had an army of five composite bowmen and a spearman. Given the way things have been going in BNW, I figured that would be enough. Well, along comes turn 104 and the Roman army shows up on my border. They have about a dozen men, including four Legions. Need I say it? The party was over. What I don't understand is how, with four cities, they were able to build and support an army of that size so early. Live and learn, I guess.