I think I just discovered another AI weakness. I assume that you already know how the AIs like to protect their resources...by pretending to come after their resources, they may abandon their fortification to come after you. Although this was a good trick, it doesn't always work. You see...if your stack is too big, they won't take the bait. Anyway, I think I just found something better; I call this one "Religious Fanatic Suicide Pact". Basically, if you camp a large stack of your force (on a hill top) right next to a holy city of their state religion, they will invoke their religious suicide pact.
Now, just turn on some music, sit back, relax and watch them die endlessly at your feet. I once emptied a holy city which was heavily defended by longbows and axemans without fire a single shot. According to the combat calculator, my stack had less than 3% of chance against their fortified bowmans. Thanks to their suicide pact, they all came out trying to storm my hill. In the end, they left a spearman to guard their city.

