Aye!
Chris is right. I usually lay siege and wait... 90% chances that someone will come to rescue those poor souls I plan to exterminate, and than... "the day is mine"
AI sallies forth when the spy opens the gates?
Hmm never happened to me... maybe because I don't use spies :D
I'm just dumb barbarian from the steppes, dunno what da "spy" is... :D
attacking army in the city vicinty is also a good idea, happened to me maybe twice...
Hoplites, hoplites... ah! those slow, humans which looks like a dead hedgehog when I finish with them ;>