In the Amerika board game, there are a few rules when attacking city territories. The first is that artillery fires first in the opening round of combat and casualties are removed before continuing. The second is each city has it’s own Anti-aircraft guns which fire before combat begins and casualties are removed. This is not like the AA guns on factories, these are for ground assault. Lastly, the attacker can only use one round of combat to simulate the difficulty and length of time it takes to capture a city. I don’t know if this would transfer well to A&A though because there is also a stacking limit in Amerka. You would never be able to capture a capital in A&A if you stacked 20-30 units on it. You could make a limit of 2 or 3 rounds or something like that though.
