Quote Originally Posted by therother
For my core cities, that are highly unlikely to face a significant enemy threat, I use peasants; I also always have an advanced army within a 2 turn "rush-in" distance if there is trouble. I always have a diplomat in each city as well, so if needs be, I'll just bribe the invaders. Although town watch are significantly better than peasants, I'd rather not have to fight with either, and peasants are better value per man in terms of garrison duty, as it's only numbers that count.
I do the same, only moreso. I use peasants exclusively. There's no significant enemy threat unless there's a significant enemy army, and that justifies a worthwhile army of my own.

The AI doesn't use its naval superiority well. I haven't had to cope with a hostile landing yet.