DarkSchneider
King
I used to think that the AI is completely inept at combat, even at the higher levels, now I have completely confirmed it. Anytime you are in a war with someone, and you are able to capture two of their cities in the same turn they will offer you huge sums of money to make peace with you, this means a) All your exposed and injured troops get to rest, and b) you are getting some decent tech/money in a process you can repeat the next two turns anyway. They will never catch on to this 
Second, anytime you are defending you own (or recently aquired) territory, just leave one of your workers (preferably captured) one square in from your opponents territory. This will draw any fast mobile unit to capture it, then you can defeat that unit, save your worker, and repeat the process until your opponent's entire knight/cavalary/tank battalion is destoryed. Once you don't have to worry about those units, feel free to march all of your fact units into the opponent's territory and take their cities. The computer always offers you more money when they have no units left to attack you with.

Second, anytime you are defending you own (or recently aquired) territory, just leave one of your workers (preferably captured) one square in from your opponents territory. This will draw any fast mobile unit to capture it, then you can defeat that unit, save your worker, and repeat the process until your opponent's entire knight/cavalary/tank battalion is destoryed. Once you don't have to worry about those units, feel free to march all of your fact units into the opponent's territory and take their cities. The computer always offers you more money when they have no units left to attack you with.