That they have other experience at war and allies worries me significantly, but that also solidifies the fact that we need to keep the pressure up. Although I doubt we'll be able to deal a fatal blow, giving them time to regrow and get stronger is clearly a mistake as the next time we roll in they'll probably have soldiers of their own and more fortifications set up. The objective here will be to cripple their food supply and gather manpower to even the population game, so next turn we can deliver the finishing strike. Perhaps we can desiccate their religious icons? Our method of 'conquering' is just spreading our religion, after all, so we need to keep the actual objective in mind.