I checked FAQ and forums but could not find the answer for my question:

When a city of mine (with auto defense bonus) is exhausted because I spent the influence points earlier, can I still apply the auto-defense bonus when another player is conducting a siege against it?

Another question, and in retrospect, this question should have preceded my previous question:

If I have Forge as one of my cities, does another player conducting a siege on it have to meet the 9 Strength cost first and then conduct combat with my army defending it? Or do the armies just conduct combat?

To your first question, yes you always get the auto-defense bonus on your cities when under siege by another player, whether your city is exhausted or not.

To your second question, an opponent does not have to meet the strength of 9 on that city. They just have to exceed your strength with their army's strength. But don't forget to add the auto-defense bonus to your strength total for that combat.

Welcome to the game! Please post if you have any other questions!

Thank you for the clarifications! This game is awesome.