How to enter the battlefield, retain advantage and then expand it, is quite troublesome.
A commander proposed the idea of building defensive structures on-site. They could have engineers utilize some buildings to construct some fortifications, like nailing a peg in the city, using the defensive structure as a springboard to expand outward.
This approach has no inherent problems, but the only drawback is that it's too slow. Constructing defensive structures takes time; by the time they are stable and then expand outwards, a few days or even a week could have passed.
They need to capture a city, not a stronghold, so this idea clearly isn't very suitable here.
Compared to such a slow approach, some commanders still prefer finding ways to destroy the enemy's equipment capable of shooting down planes, followed by saturation bombing.
Erasing the entire city from the map removes any problems.
