Your out of cannons and find yourself very outmatched. Now what? The answere is to STILL abandon some of your cities, despite you cant counter attack exploit it. The reason being, the AI seems to stockpile military units in these, even stuff it SHOULDN'T. This causes his armies to march against you with lesser units, while you get to ramp-up the odds doing so. I've seen the AI park Artillery units in abandoned cities for ages, while any human player would have eaten me alive with those. Buwahaha!